GPS World

Category: Opinions

  • Data collection of WGS 84 information — or is it?

    Location, location, location. It’s not just the tagline for real estate and sales; it’s about all of us, all of the time.

    Thanks to technology, everything revolves around location these days. It is in our cars, smartphones, exercise trackers, and even our packages. GPS has revolutionized so many things in our lives, but most people do not know how it truly works. They get the general idea of satellites beaming radio signals to Earth and translated into a position on the Earth, but that’s as far as it gets for most.

    Understanding the location relationship by points on the face of the Earth is something much more involved and gets quite complicated. Thanks to sophisticated computers and programming power, this complex bundle of formulas and computations are solved behind the scenes with little effort. All we know is that when our location shows up on our phone, we can share it with friends and family, search for the closest coffee shop, or have it tell us how long until we get home.

    This also affects professional surveyors more than many of them truly understand. The introduction of GPS has allowed many to produce work products with greater efficiency, but without understanding the true geodesy, math and positional accuracies behind the technology.

    Let’s take a look back in time to understand where we have come, to better understand why knowing the basis of datums is so important:

    IN THE BEGINNING

    Until the early 1900s, surveyors only measured what they could see and didn’t allow for any curvature of the Earth, (it is round, by the way…). Only after the introduction of long-baseline survey projects was there any consideration for adjustment to survey measurements.

    Extensive surveying observations were performed nationwide to establish a network of standardized horizontal positions throughout the land. Using least-square adjustment methods originally developed by Carl Friedrich Gauss to help with estimation of orbital movement of the planets, this network was developed using the Clarke Ellipsoid of 1866 with a base point of Meade’s Ranch, Kansas.

    The observed location of the initial point was determined at 39°13’26.686” North latitude, 98°32’30.506” West longitude; from here, all latitudes and longitudes are measured using the Clarke Ellipsoid for reference.

    This datum, called the North American Datum of 1927 (NAD27), was used extensively by government surveyors and geodesists for many decades, but because of the highly involved mathematics involved in the computations, very few private surveyors were trained to work within the datum.

    More than 26,000 survey stations were used in the computation of NAD27, all being manually observed and measured. The electronic distance meter and long-range theodolite help proliferate more reference points over time, but still required heavy-duty computation to determine results for the new positions.

    THE COMPUTER AGE

    The implementation of computers, both mainframe and personal computers, allowed for further development of programming that analyzed survey data faster and more accurately than humanly possible. This technology allowed geodesists to compute positions with more reliable results, but still lacked significant involvement by professional surveyors.

    As I’ve covered in previous articles, the development of a global positioning system by the Department of Defense created the ability to establish locations nearly anywhere. Their work started in the late 1950s with the development of an inter-continental geodetic system (World Geodetic System 1960 or WGS 60) to work with other nations. Continued refinement in the WGS data allowed for the development of a new geodetic datum that would be Earth-centered rather than the fixed-station method used by NAD27.

    In addition to the measuring method, there was also a much larger number of monuments now available for implementing into the new system. Approximately 250,000 points were included in the initial database for the new datum along with additional terrestrial and Doppler satellite data to create the North American Datum of 1983 (NAD83). Improvements with NAD83 over NAD27 included the correction and improvement of data distortion from earlier observations through the increased densification of information.

    A big difference from the previous datum was the use of the Geodetic Reference System of 1980 (GRS80) instead of the previously implemented Clarke Ellipsoid. It also offered global projection rather than localized realization of data. Because of these large differences based on projection methods, use of a larger ellipsoid and basis of coordinate values, it is somewhat easy to distinguish the difference between the two datums. But like life itself, everything is subject to change.

    BUT CHANGE IS INEVITABLE

    nga-logoThe National Geospatial-Intelligence Agency (NGA) published a Standardization Document in July 2014 outlining WGS 84, its parameters and history, along with the intended relationship with local geodetic systems.

    The standards covered in the document included:

    • Coordinate Systems
    • The use of GPS in the development of the WGS84 Reference Frame
    • Ellipsoid and its defining parameters
    • Ellipsoidal Gravity formula
    • Earth Gravitational Model 2008 (EGM2008)
    • EGM2008 Geoid Model
    • The World Magnetic Model (WMM)
    • WGS 84 relationships with other Geodetic Systems
    • Accuracy of WGS 84 and its models
    • Implementation Guidelines

    NGA continues to improve and refine the WGS 84 reference frame in order to standardize all future GNSS measurement. Let’s take a look at a few more specific characteristics of our current reference frames.

    WGS 84 BASICS

    The WGS 84 Coordinate System is a Conventional Terrestrial Reference System (CTRS). It has a right-handed, Earth-fixed orthogonal coordinate format. The system origin also serves as the geometric center of the WGS 84 ellipsoid, and the Z-axis serves as the rotational axis of this ellipsoid of revolution.

    It was established in 1987 with the intent of aligning with the Bureau International de l’Heure (BIH) Terrestrial System, also known as the BTS reference frame. Initial accuracies of the reference frame were 1-2 meters; ongoing refinement was important to the NGA team and development continued.

    The WGS 84 Reference Frame has been updated six times, with revisions taking place in 1994, 1997, 2002, 2012 and 2013. These updates are intended to incorporate international conventions and to align with the International Terrestrial Reference Frame 2008 (ITRF2008).

    Environmental changes in updated models and methods have begun to make discrepancies in the relationship between the reference frames, so improvements have been made to cause these periodic changes to the WGS 84 frame. The intent and result of each revision has been to improve its accuracy and precision, so applying constraints to WGS 84 in order to align it with ITRF results in maintaining continuity with other GNSS worldwide.

    With this latest revision to the WGS 84 reference frame, WGS 84 (G1762), the transformation differences with the International GNSS Service (IGb08) is essentially zero. This means users of the latest version of WGS 84 can use the data in its original state to translate to international measurements when necessary.

    ITRF2008 was recently updated to ITRF2014, but maintains its consistent relationship with WGS 84 (G1762) with centimeter-level accuracy.

    The original WGS 84 reference frame is still used by most consumer-grade GPS devices (smartphones, vehicle navigation, etc.). It has retained the original major-axis value to eliminate the need for various updates and modifications for these devices and mapping software. This allows existing collections of geospatial data to retain its values and not be subject to transformation or additional computation.

    NAD83 BASICS

    The NAD83 coordinate reference system is a horizontal adjustment of existing data from previous surveys, Doppler and Very Long Baseline Interferometry (VLBI) data. The geocentric datum is earth-centered/Earth-fixed, utilizes the GRS80 ellipsoid, and is intended to be identical to the original WGS 84 reference frame with the origin at the center of the mass of the Earth.

    The implementation of GPS-based data collection uncovered a discrepancy with the originally calculated center of the reference frame of up to 2 meters. This revelation rendered the reference frame flawed under its original configuration with positional errors up to 1-2 meters being commonplace.

    By 1997, additional observation data was introduced along with application of high-accuracy reference network (HARN) information to greatly increase horizontal accuracy. This was followed by the addition of continuously operating reference station (CORS) data through 2002, and then by the implementation of the National Spatial Reference System (NSRS) in 2007. The last major re-adjustment occurred in 2011 with more observation and CORS data.

    It is from this framework that the State Plane Coordinate (SPC) systems were developed for localized use. Transformation parameters were created to allow smaller coordinate values for easier use in all types for mapping and data collection. This is also where most surveyors were introduced to a simplified form of geodesy, but without the complicated formulas generally associated with its use.

    Hardware and software enhancements have made the implementation of SPC systems much easier than past computations. The continued refinement of the NAD83 system through significant adjustments and equipment upgrades has given the surveyor a lot of confidence in this system, but I still caution our profession to promote QA/QC programs to verify the information being collected. GPS data acquisition techniques are not infallible and appropriate caution during use is still required.

    SYSTEM COMPARISON

    The concept of a world geodetic system is to provide a globally dedicated reference system and to minimize or eliminate the need for local systems. The usual reason for a local coordinate system was to meet the needs for an area before the implementation of a larger system was possible. So often, the worst part of having and maintaining a horizontal system separate from a world system is the means and methods of transformation/translation of data.

    In the meantime, here are a few of the main differences between WGS 84 and NAD83:

    • While both use a similar ellipsoid, they differ slightly and thus create different results.
    • The coordinate system for WGS 84 is geographic, and the NAD83 system is projected.
    • WGS 84 values are points in space, while NAD83 coordinates are physical locations on the Earth.
    • WGS 84 is based upon the NAVSTAR satellite system, and the NAD83 system is based upon a network of ground points, observation data and CORS.
    • WGS 84 ellipsoid is defined as a geocentric, equipotential frame, whereas NAD83 considers GRAV-D data collection and tectonic plate velocities.
    • While the original WGS 84 system aligns with the NAD83 (1986) adjustment, further refinement of WGS 84 has been completed to maintain similarity to ITRF realizations.

     

    Until there is a redevelopment of the GPS system (including hardware), we must realize the limitation of each system and work together to make sure the relationship is understood by all who work with it.

    DATA COLLECTION NOTES

    With the advances in GNSS receivers, data collectors and RTK network opportunities, GPS data has proliferated greatly in the past 20+ years. What began as simple data collection with complex computing necessary to determine positional values has now turned into a plethora of available systems at your fingertips. Surveyors are now considered an “expert” in geodesy overnight, with very little education or knowledge of what they are truly measuring and publishing for coordinate and geodetic values.

     

    A majority of GPS data collection happens in a real-time network (RTN) scenario: (1) with a base station on a published coordinate point or OPUS-derived value, or (2) with a cellular-based RTN. Both situations are typically constrained by built-in NAD83 parameters within the data collector software to produce localized or state plane coordinate values. For projects that rely on these coordinates, these methods are perfectly acceptable.

    google-earthWhere the fork in the road appears is when geodetic values are required for data collection of geographic information system (GIS) database creation. Many GIS users understand the difference between WGS 84 and NAD83 data, whereas the typical professional surveyor does not. The data required for GIS use (such as Esri, Google Earth and Microsoft Virtual Earth) is typically defaulted to WGS 84 because most mapping is done for use by those with the simplest needs: the consumer. Consumers are using GPS in many personal devices, and keeping the programming and mapping requirements simple is key to their success. Excessive accuracy is not necessary when it comes to these devices, so a meter or two variations is perfectly acceptable. That is why the original WGS 84 reference frame is programmed into these devices and is still utilized for most large-scale mapping needs. But what happens when the mapping needs to be more precise?

    The need for precise data collection gets us back to the surveying community. Information collected by most surveyors is assumed to be in WGS 84 because “That’s what my data collector told me it was.” Ideally, the best way to gather actual WGS 84 values is to occupy the required locations and collect satellite data using a stationary, dual-frequency GPS receiver and noting the correct epoch and associated fixed-station GPS coordinate data used. Locations derived from data collected in local coordinate systems and transformed to WGS 84 values will be subject to characteristics and distortions potentially affecting the local system. This leads your subject data down an uncertainty path that may not be acceptable to your delivered product.

    Typically, data collected in NAD83 (2011) is in the 1- to 2-meter accuracy range from WGS 84 as previous discussed. These accuracies are not usually acceptable in the surveying world and hopefully not in most GIS base-layer situations either.

    One of the best solutions for high-accuracy data collection that will be more compatible with GIS database needs is to start your data collection with ITRF-based points, if possible. This method keeps your data consistent with current WGS 84 reference frame parameters and will fit seamlessly into most systems as required. Most hardware and software systems allow for its implementation as a coordinate system option and is just as easy to use as our normal NAD83 based systems. This helps provide less headache with data correlation to the client’s requirements and keeps the playing field closer to level.

    For surveyors, here’s the bottom line: our responsibility is to provide the client data in the most accurate and precise condition possible. Our profession needs to re-educate ourselves to better understand what the data collector is truly producing rather than relying on a wing and prayer that it meets the client’s needs.

    Think back to your early math class days; we spent many hours learning trigonometry functions by hand before we were turned loose with a calculator with sin, cos, and tan buttons. Learning longhand what was being produced helped us to understand how those complex calculations were completed.

    We need to think of this GPS data collection process in the same manner, and not just hope the “ghost in the machine” spits out the right numbers for the project. The worst thing you can tell a client is that you “think” the data is correct because you’re just not sure…

    BUT THERE IS GOOD NEWS…

    The good news for geographic data users in the United States is that the National Geodetic Survey (NGS) is working on a new datum that will incorporate radical new changes in combining horizontal and vertical datums. Visit the NGS website for more information. The initial framework sounds very robust and user-friendly, so keep your eyes and ears open for more details as they develop. I’m looking forward to the new system and so should surveyors everywhere.

    The problem sometimes with technology is that it moves forward so quickly  that good innovations get passed over due to previous acceptance and reluctance to upgrade (such as Sony Betamax, Microsoft Zune, etc.). This has been true with geodetic datums and the introduction of GPS for mainstream use. It will be an age-old issue, but I look forward to better and brighter days ahead.

    Now, where did I leave my trusty Junior Geodesist Secret Decoder Ring?

  • Canada, US workshops focus on PNT threats

    Canada, US workshops focus on PNT threats

    Two workshops convened in recent weeks in the U.S. and Canadian capitals, respectively, sought to bring into focus looming threats to the nations’ positioning, navigation and timing capabilities and critical infrastructures. Some of the threats are pervasive — jamming and spoofing — and formed the general topic of the Canadian workshop. Some threats are specific — powerful terrestrial transmitters overwhelming GPS/GNSS receivers — and occasioned the U.S. gathering.

    Canada. In a first for Canada, the October 21 GNSS Vulnerabilities Innovation Policy (VIP) Workshop brought together 19 federal government departments as well as  provincial and municipal agencies and private sector companies.  U.S. State Dept. and Homeland Security gave presentations, as did the European Space Agency, Bell Canada, NovAtel and Spirent Communications.

    Integrity challenge for automotive positioning, presented by NovAtel
    Integrity challenge for automotive positioning, presented by NovAtel

    The workshop was sponsored by the the Federal Global Navigation Satellite Systems Coordination Board (FGCB), a government board with representations from various government departments and agencies. The GNSS Coordination Office (which organized the workshop) is hosted at Canada’s Ministry of Innovation, Science and Economic Development and sponsored by the FGCB members.

    Presentations covered such topics as Demonstration of the Geolocation of GPS Jammers, GNSS & the Telecom Sector, Detecting and Protecting Against GPS Cyberthreats, and Safety Critical, High Precision, GNSS Positioning for Autonomous Vehicles.

    United States. The U.S. Department of Transportation (DOT) hosted its fifth workshop on the GPS Adjacent-Band Compatibility Assessment effort on October 14. This lengthy, thorny and occasionally acrimonious process started out benignly enough in 2010 with the statement, “Demand for commercial spectrum to support broadband wireless communications has led the government to consider repurposing various radio frequencies, including the satellite communications bands next to GPS.”

    The workshop discussed the results from testing of various categories of GPS/GNSS receivers including aviation (non-certified), cellular, general location/navigation, high precision and networks, timing, and space-based receivers. The workshop also included a discussion on the development of use-case scenarios for these categories — which is where the going got heavy and differences of opinion truly emerged.

    DOT has posted all presentations from the workshop.  Scroll down to “October 2016 Workshop.”

    The furor stems from a renewed effort by Ligado, formerly known as LightSquared and now re-emergent from a 2-year bankruptcy process, to convert relatively inexpensive satellite-to-earth spectrum into very valuable terrestrial spectrum. The company stands to gain billions of dollars and secured rights from the process.

    Members of the DoT team presented the first results from the GPS Adjacent-Band Compatibility (ABC) Assessment, an effort to determine the power limits by frequency, or interference tolerance masks (ITM), needed to protect both existing and future GPS receivers. Test results indicated a need to limit interfering signals at different levels depending on the type of receiver being used. 80 receivers in six categories were tested: cellular, general location/navigation, general aviation, timing, high precision and space receivers. Certified and military receivers are undergoing separate tests.

    The tests of current receivers took place April 25–29 at White Sands Missile Range, New Mexico, using a 100 x 70 x 40 anechoic chamber. The signals used in the test included GPS L1 C/A-code, GPS L1 P-code, GPS L1C, GPS L1 M-code, GPS L2 P-code, SBAS L1, GLONASS L1 C, GLONASS L1 P, BeiDou B1I and Galileo E1 B/C. Tests were conducted within 100 megahertz on either side of the GPS L1 center frequency of 1575.42 using a 10-megahertz LTE signal and a narrow bandwidth 1-megahertz bandpass white noise signal.

    The tests were conducted for GPS and GNSS receivers processing signals in the 1559–1610 MHz Radionavigation Satellite Service (RNSS) frequency band, as well as receivers that process Mobile Satellite Service (MSS) signals in the 1525–1559 MHz band to receive differential GNSS corrections.

    The tests determined the power levels at which each device experienced a one-decibel degradation in the carrier-to-noise density ratio (CNR) at a particular frequency. The DoT team graphed results for each device. The recommended power limits were the lowest in frequencies closest to the GPS bands.

    The receivers most affected by the test transmissions were identified as high-precision receivers. They experienced interference at power levels as low as –90 to –95dBm at around 1550 MHz and –90 dBm at roughly 1610 MHz.

    highprecision-gps-l1-receiver-category

    The strictest limit for both the general aviation, general navigation/location, and timing receivers was a little below –80 dBm at about 1550 MHz, while space-based receivers were equally sensitive on both sides of the RNSS band with the toughest limit being about –85 dBm.

    FAA. The Federal Aviation Administration (FAA) has authority to set power and out-of-band emissions limits to meet aviation safety standards, and it had been thought that these limits might  address interference with other types of receivers as well. But the test results showed that “protecting the FAA-certified mask does not necessarily protect the rest of the receiver categories,” according to Hadi Wassaf, technical lead for GPS interference analysis at DoT’s Volpe Center.

    Use Cases. Ligado has proposed that position error as experienced by the user is a better guide to interference levels than degradation in the carrier-to-noise density ratio. The GPS community generally opposes this approach. The next step is the development of use cases. According to the test plan, use cases define the regions of operations for a receiver, and they identify applications that “that are vital to economic, public safety, scientific, and/or national security needs and any other factors supporting why this particular receiver model is important to be tested (e.g., quantity in use, economic impact, etc.).”

  • How to dissolve funding logjams in Congress

    [Editor’s note: This is the Signals Leadership Award acceptance speech given by Clark Cohen at GPS World’s 2016 Leadership Dinner in September. The Award was recognized the development of alternates to GPS based on communication satellites: a method for adding high-accuracy ranging capability to Iridium by modifying the transmitted signal structure of an already flying, programmable constellation. ]

    Thank you GPS World, industry sponsors, and colleagues who engaged in the selection process. I appreciate the honor.

    The Advanced Waveform was the second and most ambitious broadcast that we developed for the DoD-sponsored iGPS program. It is a wide-bandwidth (10 MHz maximum spectrum allocation), near-white, high-power broadcast with independently resolvable code and carrier capable of illuminating regions of the world at any time. Yet Iridium was never designed for navigation.

    I am grateful to the Naval Research Lab, the Office of the Secretary of Defense, Boeing, and Iridium for their support. Also, many capable people comprised our team. Completeness is impossible, but I’ll highlight the efforts of Dick Cervisi, Kamran Ghassemi, Ann Stevens, Robert Scholl, Tom Guffey, Bernie McCormick and Mark Psiaki.

    The commercial Iridium constellation is built on billions of dollars of private capital. Meanwhile, the iGPS overlay required Congressional appropriation. But if the technical part weren’t challenging enough, the politics were, in my view, a bit too hard.

    My topic is the future of public-private partnerships. Such partnerships include the GPS space and ground segments and most other government projects. Our broken, inflexible Congress is not helping. My answer here for the family dinner table is not political — it’s structural, non-partisan, systems engineering.

    We can do better than handicapped innovation, winner-take-all procurements, Nunn-McCurdy triggers, continuing resolutions, debt-limit brinksmanship and government shut-downs. This is not to judge people. Good people are operating under imperfect rules.

    House elections now resemble a stuck, one-bit, analog-to-digital converter. Hundreds of individual races, cumulate the equivalent of input noise and bias, rendering the House largely unresponsive to voters. Consent of the governed demands a healthy, moderating feedback loop from people to representatives to laws and back. Cutting this loop spells trouble.

    A major root cause of dysfunction is winner-take-all, single-member districts. Geographical voting made sense in the 18th century. But in an increasingly complex, connected world, where you live is no longer a stand-in for what you think.

    We need to start dissolving district boundaries themselves. An elegant approach is aggregating adjacent single-member districts into larger multi-winner “super districts” with three to five members each. A refinement called Ranked Choice Voting eliminates spoiler hazard and incentivizes positive campaigns. No change to the Constitution is needed — only passing a law.

    We should reset our expectations. Congress should be able to pass the nation’s budget on time every time. We don’t need drama around GPS modernization, backup terrestrial navigation, and spectrum protection. And America should boldly pioneer aspirational, cathedral-and-moonshot-scale, public-private initiatives.

    Working hard and playing by the rules implies a value-added, positive-sum relationship with society. But to the extent that the rules are imperfect, don’t vestiges of zero-sum exchange imply collateral damage somewhere in society? Voters are rebelling by the millions. We should pay attention. America’s defining Revolutionary War was fought over taxation without representation.

    Whether applied to sword or plowshare, precision feedback from GPS provides guidance to help minimize collateral damage. Updated voting rules will do the same for the nation. Everyone benefits from more efficient and effective execution. Yet perhaps our greatest harvest — should we choose to claim it for ourselves and our children — will follow from sowing new seeds of discovery and innovation through public-private partnerships on a vast and visionary scale.

     

  • Utility GIS users meet at Esri GeoConx

    I spent time this week at the Esri GeoConx conference in Phoenix, Arizona. The GeoConX conference is a gathering of ~800 GIS users from gas, electric and telecom utility companies.

    I always enjoy listening to GIS professionals from utility companies because they are faced with the most interesting GIS and data management problems. High on the list is data integration. Not necessarily the integration of disparate GIS datasets (although that’s an ongoing challenge), but rather GIS data integration with other systems that manage work orders, financial systems and more.

    geoconx-1-w geoconx-2-w

    I took a lot of pictures at GeoConX and I think they tell an interesting story about the issues GIS professionals at these utility companies are facing.

    geoconx-3-w

    Eight hundred people from 44 U.S. states, and countries as far away as New Zealand, attended GeoConX.

    Esri President Jack Dangermond re-emphasized the System of Record (authoritative data source), System of Engagement (collaboration/sharing), and System of Insight (analytics) concept that he introduced at the 2015 Esri International User Conference.

    He also made a comment, which he has before, that Esri spends ~27 percent of Esri’s annual revenue on research and development. That’s about $230 million per year. To put in that perspective, in 2015 Apple Computer spent 4 percent of its revenue on R&D. Renown automobile innovator Tesla spent ~18 percent of its revenue on R&D. Toyota spent 4 percent.

    Granted, those companies have significantly higher annual revenues than Esri, but you have to give Esri kudos for re-investing and keeping the company ownership closely held. If Esri was a public company, or had significant external shareholders expecting typical investment ROI (Return on Investment), shareholders would want a piece of that R&D budget in their pockets.

    A devil’s advocate might say that a different corporate structure might pressure Esri to be more efficient with R&D spending, but I have a lot of respect for Esri’s chosen business model, which enables it to remain ably nimble.

    geoconx-4-w

    Location-based services are “hip.” The 18- to 29-year-old demographic leads the pack in all usage categories. Getting “kick-back” from employees who are hesitant to trust or embrace GIS technologies? Just wait a few more years as the 18-29 demographic works its way through age groups like a rat in a snake’s belly.

    geoconx-5-w

    This slide will be interesting to those of you whom have asked where GIS lies in the adoption curve. According to Esri, GIS technology adoption has passed through the “early adopter” stage and is building momentum with the “early majority.”

    geoconx-6-w

    The BART (Bay Area Rapid Transit) presented its implementation of enterprise GIS. I’ve heard similar stories in the past, but perhaps their most interesting data was the statement that BART has derived $3.11 in value for every $1 invested in GIS technology.

    geoconx-7-w

    A look at Esri’s software release schedule for the next year.

    geoconx-8-w

    Tracking and traceability was one of the hot topics, especially in the natural gas industry. While the natural gas industry is driving the technology, once it’s developed there’s no doubt the concept and technology will seep into other industries. Better systems and data = better decisions and accountability.

    geoconx-9-w

    NYSEG/Avangrid gets my vote for “quick and dirty” mobile GIS deployment of the year. Six months, 300 iPads, develop app, train staff, deploy tablets. No enterprise-level MDM (Mobile Device Management) system. Don’t accept that iOS 10.x update prompt!

    geoconx-10-w

    Construction as-built data should be treated as a valuable asset, not a luxury that can be cut at the end of the project. As one who has created many construction as-built maps over the years, they are preaching to the choir. An accurate construction as-built housed in an accessible database is worth its weight in gold.

    geoconx-11-w

    This slide shows “decreased GPS performance close to buildings and under trees.” Please read my column from last month.

    geoconx-12-w

    Last but not least…

    This slide is worth a thousand words. It succinctly illustrates the problem facing nearly all enterprise GIS that are loaded with legacy data.

    This particular slide describes new attributes that are being added to Esri’s pipeline data model. The driver of this action is the fact that GNSS data being collected is likely more accurate than the legacy vector data. It doesn’t matter if it’s a pipeline, a tract boundary, a valve or any other infrastructure, the age-old question is “Why doesn’t my GPS data line up with my basemap?” The answer, nine times out of 10, is because the basemap is less accurate than the GNSS data. Therein lies the rub.

    When this situation occurs, there are two choices:

    1. “Move” the basemap data (I’m being overly simplistic) to match the more-accurate GNSS data.
    2. “Move” the more-accurate GNSS data to match the less-accurate basemap data.

    Common sense tells one to move the less-accurate basemap data to match the more-accurate GNSS data. However, moving basemap data can lead to all kinds of challenges. It’s the GIS house of cards. If you start moving the cards at the bottom of the structure, the foundation becomes weak and you’ll likely need to rebuild other parts of the basemap, which can be quite an undertaking.

    To that point, coordinate fields (GPSX and GPSY, and soon-to-be GPSZ) are added as attributes to store the high-accuracy coordinates of the features. Then, believe it or not, the more-accurate GNSS data is moved to match the less-accurate basemap! It seems counterintuitive, but the logic is that sometime in the future as the basemap data evolves and accuracy improves, the high-accuracy coordinate values of the features are preserved as attributes and can be “brought out of storage” and placed into service at an appropriate time in the future.

    Almost every enterprise GIS faces this problem. How are you handling it?

    Thanks, and see you next month.

    Follow me on Twitter at https://twitter.com/GPSGIS_Eric

    Photos: Eric Gakstatter

  • Why tether drones? Plus: Trimble divestiture, Intel expansion, ISIS

    Why tether drones? Plus: Trimble divestiture, Intel expansion, ISIS

    I’ve always thought that tethered drones would have a major disadvantage over regular flying vehicles, in that their range is really limited and therefore their applications would be few and far between. However, a recent release by Drone Aviation got me thinking otherwise.

    The company is taking the route many tech companies have followed to protect their technology and enhance their market position, by patenting unique technical elements — in this case, the Electric Tethered Aerial Platform (ETAP) technologies of their drone tether system.

    So why the change of heart about tethered drones? The drone industry is becoming increasingly specialized in its offerings, so why not drones and aerostats with the advantage of no detectable uplink or downlink transmissions, which can also stay aloft for 8+ hours? You might even load the base into a truck and move the area of operations around. Maybe more use to the military for somewhat covert reconnaissance missions, but Drone Aviation indicates that applications such as newsgathering, law enforcement, infrastructure and pipeline inspections, and event management would also benefit from longer endurance drone operations.

    Anyway, someone thinks this is a good idea, because Drone Aviation was just awarded a $400,000 contract by a “U.S. Department of Defense (DoD) customer” for WAAT electric tethered drones, plus complete in-field support packages and operator flight training.

    drone_inspectionAnd don’t forget those ads currently running on TV with dual operators inspecting oil refinery stacks using a free-flying six-rotor drone — maybe BP would also feel somewhat safer avoiding potential refinery-stack collision damage if the video inspection drone were to be tethered?

     

    Trimble and 3D Robotics Divest

    One of the hot-news items of the month has to be that Trimble has divested its UAS mapping business that it bought from Gatewing in Belgium in 2012. Having worked in this sector for the last four years, Trimble decided to concentrate on core software technology for UAS that integrates positioning, remote sensing and photogrammetry.

    Delair-Tech in Toulouse, France, has acquired the Trimble UAS business for undisclosed terms. Delair is already a supplier of long-range, fixed-wing UAS solutions for industrial inspection and asset management applications, and intends to grow the acquired business by joining the Trimble UAS business to its existing portfolio of airborne mapping solutions.

    Trimble has not entirely disconnected from its UAS business — rather, it has also formed a strategic alliance with Delair-Tech as a preferred provider of fixed-wing UAS solutions, with Trimble providing software, data processing and deliverables to UAS operators across multiple vertical markets. To ensure full segment coverage, Trimble has also joined up at the same time with Microdrones in Siegen, Germany, an existing provider of multi-rotor UAS solutions, under another preferred-supplier strategic alliance. Both Delair-Tech and Microdrones will support Trimble distributors to provide UAS mapping solutions for Trimble’s customers around the world.

    It’s easy to guess that Trimble may have found that directly competing in this emerging airborne mapping market to be harder than it looked, with many existing capable UAS operators and a market that is perhaps developing more slowly than expected. So stepping back to focus on its core competences and selling what it does best should cost less and allow it to address all airborne operators, rather than competing with all of them. Not a pattern that Trimble may have followed closely in the past as it entered more and more market segments, but one that might let it more easily pick winners in the UAS segment.

    And for 3D Robotics in Berkeley, California — the company that was seen as the U.S. supplier of drones at one time with its Solo and 3DR drones systems — it, too, is out of the UAV platform manufacturing and supply business. In just 12 months, the company has gone from the height of being an industry-leading drone startup to dumping its drone products. As a consequence, 3D Robotics has laid off more than 150 people and spent a good part of its initial funding.

    Poor sales at the beginning of the year and highly competitive drone products, mostly from DJI, have forced a move away from consumer drones. Initial production problems may have also doomed the launch of its commercial drone products.

    3D Robotics CEO Chris Anderson flying solo.
    3D Robotics CEO Chris Anderson flying solo.

    Although 3D Robotics might be up against the ropes, it is retrenching and, like Trimble, is focusing on the development of software and service applications. CEO Chris Anderson has declined to discuss his company’s financial situation, but has said that 3D Robotics is now solely focused on enterprise software.

    ISIS Flies Explosive Drones

    An unwelcome use of UAVs has now unfortunately emerged in Iraq. Kurdish forces fighting ISIS in northern Iraq last week shot down a small drone. They believed it was just one of many commercially available drones, such as the DJI Phantom, which have been seen flying reconnaissance missions, so they picked it up to transport it back to their outpost to examine it.

    Unfortunately, the drone had been rigged with on-board explosives disguised as a battery, and the device exploded, killing two. Of three known such drone attacks in Iraq, only this one has apparently caused casualties. There was only a small amount of explosives, but it was enough to kill. There may be several known existing systems that can be used to defeat such attack drones, but the equipment needed has not yet reached this war zone.

    Intel Extends Its Presence

    On a much happier note, while Trimble and 3D Robotics are getting out of UAVs, Intel is extending its UAS market presence with the launch of an improved Falcon 8+ system, now marketed for the first time under the Intel name.

    Intel Falcon 8+ octocopter drone.
    Intel Falcon 8+ octocopter drone.

    The UAV has full electronic system redundancy with redundant batteries, redundant communication between critical flight components and redundant aerial sensing. A triple-redundant autopilot uses three redundant inertial measurement units (IMUs) that compensate for environmental issues like strong electromagnetic fields or winds, and the vehicle also carries high-precision GPS.

    The Intel Falcon 8+ is aimed at industrial inspection, surveying and mapping, and is geared toward professionals and expert use. The system is capable of detailed images with millimeter accuracy and can provide structural analysis that helps users detect and therefore prevent more damage to infrastructure. Structural inspections can be run time and time again to monitor for wear and tear, as this UAV has repeatable waypoint navigation capability.

    Mock Medical Delivery

    Exploring another opportunity where the use of drones may improve life for the rest of us, UPS and CyPhy Works recently demonstrated the delivery of medical supplies to an island off Marblehead, Massachusetts.

    ups_medical_delivery_uavDuring the mock delivery, the Persistent Aerial Reconnaissance and Communications (PARC) UAS flew from Beverly, Massachusetts, to Children’s Island, about three miles off the coast, delivering an asthma inhaler to a child. UPS is investigating the use of drones for the delivery of humanitarian aid around the world, and at home is also testing drones to verify their warehouse stock.

    And finally, Heliceo in Nantes, France, has come up with the DroneBox, which contains most of the electronics you might need for a drone of your own making, or you could also buy one of Heliceo’s several complete drone models and systems built around the DroneBox.

    Heliceo’s patented solutions are available to suit both plane and multi-rotor drones. The unit contains GNSS RTK receivers, an autopilot, telemetry, data storage, communication, a flight controller and avionics. The DroneBox RTK is a “technology concentrator,” and with its 24-million-pixel camera is capable of detecting a coin from around 500 feet. Heliceo claims that its integrated solution can contribute up to 70 percent of the value of the entire drone.

    The box is equipped with two GNSS receivers (one for navigation and one for Trimble RTK measurements), and the camera is optimized by a calibration process that corrects optical lens aberrations. Each acquired image is recorded with its latitude, longitude and altitude, which allows the subsequent creation of georeferenced 2D scaled maps or 3D digital terrain models.

    So several steps forward for various UAV/UAS initiatives, some things from which we can still learn, and maybe a couple of steps back for a fledgling industry facing inevitable consolidation. But at this stage, it’s good to see there is still enough investment and enthusiasm to take on a wide range of opportunities. Some will fail, some will succeed, and the winners will hopefully find ways to further improve our way of life and hopefully make money in the process. And for goodness sake, let’s get some new or existing anti-drone solutions out there soon for U.S. troops and their allies.

    Tony Murfin
    GNSS Aerospace

  • Intergeo 2016 is buzzing

    Intergeo 2016 is buzzing

    Yes, there are drones everywhere. Drones of every size from mini electronic insects to a rather nice Zeppelin remake that is cruising around Hall 4 at the Hamburg Messe. Will Intergeo 2016 mark “peak drone?” I’m thinking not.

    The two main drivers of this year’s Intergeo conference are digitization and smart data, including Building Information Modelling (BIM). Hamburg itself is working at becoming a smart city, and the role of geodata and geospatial information is key to achieving the city planners dream of fast and efficient services for its “e-citizens.”

    Remarkably, this key role is not always initially appreciated by ‘smart city’ innovators. Nigel Clifford, CEO of the UK’s venerable Ordnance Survey pointed out in the plenary conference session that the perception of the value derived from geospatial data is changing as location data “uniquely unlocks value in others’ data.” He also coined the term Geovation – something we will be hearing more about in years to come I am sure.

    At the Trends in GNSS Positioning session, I was surprised to hear (or at least this how the translation came over) that both Herbert Landau of Trimble Terrasat GmbH and Bernhard Richter of Leica Geosystems were suggesting that if you bought their latest RTK/ PPP systems, you would never need to buy another one! Both had similar reasons: their systems had a “gazillion channels” for receiving positioning data, were equipped for multiple communication modes (terrestrial and satellite-based), had low power requirements but powerful computing on board, were easily portable, and the fact that in the near future some 120-140 GNSS satellites would be in the sky. This plethora of signals and multiple frequencies will allow a whole range of new possibilities.

    Along these lines, NavCom Technology announced the release of its Onyx multi-frequency GNSS OEM board. Offering integrated StarFire/RTK GNSS capabilities, Onyx features 255-channel tracking, including multi-constellation support for GPS, GLONASS, BeiDou and Galileo.

    Galileo Coming On Strong. Talking of new signals in space, what is the news on Galileo Initial Services?  Reinhard Blasi of the European GNSS Agency (GSA) gave an update at the conference, and we can expect to see Initial Services by “the end of 2016.” Reinhard thinks that once services are established, Galileo will be in a leading position as GPS is between system upgrades and the E5 signal has some unique features.

    Figure 2.2: Normalized autocorrelation functions for different modulations: BPSK of GPS L1, BOC of Galileo E1 with simplified demodulation4, CBOC of Galileo E1 and AltBOC of Galileo E5 signals5. Source: [Silva et al., 2012]
    Figure 2.2: Normalized autocorrelation functions for different modulations: BPSK of GPS L1,
    BOC of Galileo E1 with simplified demodulation4, CBOC of Galileo E1 and AltBOC of Galileo E5
    signals5. Source: [Silva et al., 2012]
    Galileo for Mass Market. This belief was supported at the ceremony for the Young Surveyors competition organised by the Council of European Geodetic Surveyors (CLGE) at the end of the first day at Intergeo. In the Galileo, EGNOS and Copernicus category the winner was Cecile Deprez from the University of Liege. She had looked at the possibilities for greater precision in mass market applications that might be possible by accessing the Galileo E5 AltBLOC. And the answer is yes it can. In fact she described the performance as “outstanding” compared to other GNSS signals. Which is probably fair comment.

    See what you think. Along with Desprez “Relative Positioning with Galileo E5 AltBOC Code Measurements,” you can find all the papers entered for the award on the CLGE website: http://www.clge.eu.

     

  • Expert Opinions: New US FAA rule on UAVs

    Q: What is the single most important take-away from the new Federal Aviation Administration rule on UAVs?

     

    simon_al-rockwell-collins
    Al Simon, Marketing Manager, Navigation Products, Rockwell Collins

    A: This regulation brings some stability to industry looking to invest in UAS operations and should stimulate technology development that benefits all classes of UAS. This first step should also allow the FAA to turn their attention to the more compelling parts of the market such as Beyond Visual Line of Sight operations and integration into the non-segregated airspace like Class A and Class E.

    Mitch Narins, Principal, Strategic Synergies
    Mitch Narins, Principal, Strategic Synergies

    A: UAV proliferation and safe operation is and will be a continuing challenge. Two of the many concerns I have are: the means that state and local governments will be able to be involved in UAS operations, specifically with privacy issues, as I am sure that the FAA does not want to deal with local complaints; and the FAA’s continued acceptance of GPS/GNSS sole means for positioning, navigation, and timing information and, in the case of UAS, potentially to support command and control links.

    Eric Gakstatter Contributing Editor, GIS & UAV, Geospatial Solutions
    Eric Gakstatter
    Contributing Editor, GIS & UAV, Geospatial Solutions

    A: The new UAV FAA Part 107 rules, effective August 29, 2016, opened up the entire United States to the world of UAVs for business use. Part 107 rules significantly lower the barrier to operating UAVs for business by no longer requiring the traditional FAA pilot certificate to operate a UAV for business. The response to the new rules echo the hyper-demand for UAVs for business use. In the first 15 days, more than 5,000 people took the Part 107 test.

  • High plains PNT: Awareness and sense of place

    The plenary talk by John O’Keefe at ION GNSS+ stimulated a lot of neuron firing inside this old noggin. For a synopsis of “The Positioning System of the Brain,” see this column by Managing Editor Tracy Cozzens. I had the difficult task of following this brilliant scientist to the podium and introducing ION’s track chairs for previews of the conference’s technical content. Here’s how I attempted to stitch together the two parts of the evening program.

    Dr. O’Keefe’s talk called two things powerfully to my mind. The first is us, here, now. In the Oregon Convention Center, where we have gathered four times before. How do we remember its hallways, spaces, electronic stairways? What will direct us to technical sessions over the next three days? Our neural system enables us to orient within an environment, to navigate from one place to another and to remember spatial information. I’ve always struggled to understand aspects and workings of memory. Now to find that place is a key driver, that’s powerful.

    The second thing it called to mind is a book I read forty years ago, that has lingered with me since. In Cheyenne Autumn, Mari Sandoz evokes the Native American precursive sense of place. Both past and future exist simultaneously in the present. When the nomadic tribe on their annual migration cycle rode to their summer hunting grounds or through their autumn passages, the events in their past that took place in those areas became very much alive in their awareness. And the figures from their history spoke to them and rode with them through the sandhills, ravines and river crossings of Nebraska and Wyoming.

    In their tragic 1878 outbreak for freedom, the Cheyenne eluded the technological might of the U.S. Army sent to intercept them. They did so through their multisensory connection, through memory, to place and direction. Though ultimately defeated, they left us a legacy, an awareness, a state of mind to nurture: understanding memory — with place. And understanding place — with memory.

  • Analyzing NGS’ GPS on benchmark dataset used to make GEOID12B — Part 9

    Analyzing NGS’ GPS on benchmark dataset used to make GEOID12B — Part 9

    These columns have focused on procedures and routines for establishing GNSS-derived orthometric heights. There are many ways to analyze and investigate GNSS data and adjustment results. I have provided some basic concepts that I believe are important for users to understand.

    The selection of constraints is a very important part of establishing accurate and consistent NAVD 88 GNSS-derived orthometric heights. All of the analysis and recommendations have been based on using the National Geodetic Survey‘s latest scientific geoid model.

    I recommend first performing the analysis using the scientific geoid model because the hybrid geoid model has been warped to be consistent with the published NAVD 88 values. However, as mentioned in Part 7 (June 2016), in practice, GNSS-derived orthometric heights are incorporated into the NAVD 88 using the latest hybrid geoid model GEOID12B. This column will focus on the NGS “GPS on BMS (GPSBM)” dataset that was used to create the hybrid geoid model.

    As mentioned in Part 3 (October 2015), the hybrid geoid model is designed to fit the published NAVD 88 leveling-derived orthometric heights. Saying that, the GPSBM dataset can be used to identify potential issues in the NAVD 88 published orthometric heights. GNSS users should be familiar with this dataset and how it can be used in their analysis. This column will provide tools and routines that can be used to identify potential issues in NAVD 88 heights and/or NAD83 (2011) published ellipsoid heights.

    The National Geodetic Survey provides information on the bench marks occupied by GPS that were used to make GEOID12B.

    The write up from the NGA website is given below. I have highlighted a few sentences that I’ll address in this column.

    Write up from: GPS On Bench Marks (GPSBM) Used To Make GEOID12B

    Each of the below regions uses variants of the NAD 83 reference frame and a local vertical datum. Several versions of NAD 83 exist conforming to significant plates: Pacific, Mariana, and North America. Likewise, each region has its own vertical datum. It is not possible to level across water, so islands will have selected a tide gauge to serve as the local datum point and all leveling is tied to that site. The only exception to this is Hawaii. No tide gauge was selected in the Hawaiian Islands and no vertical datum has been established as of yet. Hence, GEOID12B in Hawaii transforms between NAD 83 (PA11) and the same geopotential (geoid) surface as the USGG2012 model ( W0 = 62636856.00 m**2/s**2).

    Items that are listed in the below table include the final GPSBM files for each region as both Excel spreadsheets and text files as well as thumbnail images linked to larger images showing the distribution of the GPSBM’s. Alaska and the island regions are more consistent, so not many points were dropped and each is provided in its own spreadsheet/text file and identified with the appropriate ellipsoidal reference frame and level datum (see below).

    The most significant work occurred in the COnterminous United States (CONUS). For CONUS, there were 24,782 points with 911 rejected leaving 23,961. These were supplemented from the OPUS-database with 737 points of which 238 were rejected leaving 499. There were also 579 points in Canada with 5 rejected leaving 574. In Mexico, there 744 of which 497 were clipped since they were too far south and another 70 were rejected leaving 177. This brings a total of 26,932 points of which 1,721 were rejected or clipped and 25,211 retained for modeling GEOID12B. The data in Canada and Mexico provide continuity up to and across the U.S. borders but do not make the GEOID12B model valid in those countries.

    Points were rejected either because the State Advisor recommended it be dropped (e.g., known subsidence region), the residual ellipsoid height errors (from the NA2011 project) indicated a point was too noisy in comparison to other points in a state/region, the orthometric height was suspect, or the residual errors during geoid modeling were too high. The corresponding error flags are ‘S’, ‘h’, ‘H’, and ‘N’ as seen on the spreadsheet and text files. These points then represent the control data that were used to define the transformation between NAD 83 and NAVD 88 for CONUS.

    The control data were much simpler in other regions due to the lack of quantity (more than two orders of magnitude less). Data in these regions follows a similar pattern where some data are rejected based on the codes given above for CONUS. The columns on the right side give the respective datums realized by GEOID12B for each region.

     

    REGION Excel Spreadsheets GeoPDF maps Ellipsoidal Reference Frame Vertical Datum
    CONUS (xlsx)  ,  (xls) CONUS NAD83 (2011) NAVD88
    Alaska (xlsx) ,  (xls) AK NAD83 (2011) NAVD88
    Puerto Rico (xlsx) ,  (xls) PR NAD83 (2011) PRVD02
    U.S. Virgin Islands (xlsx) ,  (xls) USVI NAD83 (2011) VIVD09
    Am. Samoa (xlsx) ,  (xls) AS NAD83 (PA11) ASVD02
    Guam (xlsx) ,  (xls) Guam NAD83 (MA11) GUVD04
    CNMI (xlsx) ,  (xls) CNMI NAD83 (MA11) NMVD03

    Table 1 is an excerpt of the excel spreadsheet for the GPSBM dataset and provides a sample of the contents. The headings of the columns are fairly self-explanatory. What’s important here is that the excel spreadsheet provides the name, latitude, longitude, NGS’ PID, the ellipsoid height and orthometric height of the stations used in making GEOID12B.

    Table 1
    Excerpt of the Excel spreadsheet for GPS on benchmarks (GPSBM) used to make GEOID12B.
    table1-excerpt-gps-bench-marks

    The “GPS On Bench Marks (GPSBM) Used To Make GEOID12B” write up states that 1,721 stations were rejected and were not used in developing the hybrid geoid model. It also states that for the conterminous United States (CONUS), there were 24,782 stations with 911 rejected leaving 23,961. This column is going to focus on CONUS but the analysis can be performed everywhere.

    As the write up states, stations were rejected for four different reasons:

    • Code S – The State Advisor (now called Regional Geodetic Advisors) recommended it be dropped,
    • Code h – The residual ellipsoid height errors from the NAD 83 (2011) project indicated that the point was too noisy,
    • Code H – The orthometric height was suspect,
    • Code N – The residual errors during geoid modeling were too high.

    These rejected stations were not used to make the hybrid geoid model but since the hybrid geoid model is distorted to fit the NAVD 88, these rejected stations as well as stations nearby the rejected stations should be re-evaluated using the latest scientific geoid model, e.g. xGeoid16b.

    So, what should the user do with the GPSBM table? I recommend that users perform the following steps when analyzing the stations in the GPSBM table.

    • Step 1: Compare the modeled GEOID12B (N12B) value to the computed GPS/Leveling (h minus H) value using the following formula: Published N12B from the NGS data sheet minus (ellipsoid height from the GPSBM table minus orthometric height from the GPSBM table). We discussed this procedure a year ago in Part 3 (October 2015). It should be noted that the orthometric height in the GPSBM table may be different than the published NAVD 88 height on the NGS data sheet if the station has been readjusted since the GPSBM table was created.
    • Step 2: Repeat the procedure in Step 1 using the latest NGS experimental geoid model, e.g. xGeoid16b. At this time, NGS only provides the experimental geoid models referenced to IGS08 so the user will have to use NGS’ xGeoid16 web tool to obtain the station’s IGS08 ellipsoid height and xGeoid16b value. The input to the tool is the station’s NAD 83 (2011) coordinates (latitude, Longitude, and ellipsoid height). [An example of using the xGeoid16 web tool is provided in the box titled “Example of Using NGS xGeoid16 Web Tool.”] As discussed in Part 3 (October 2015), the user will have to remove a bias and trend based on the differences in the region.
    • The user could also transform xGeoid16b/IGS08 geoid values to xGeoid16b/NAD 83 (2011) geoid values using their own tools, and then remove a bias and trend based on the differences. Michael Dennis, a PhD candidate at Oregon State University, created an ArcGIS raster of the xGeoid16b model, where his model has been referenced to NAD 83 (Michael L. Dennis, RLS, PE, MS Civil Eng., Geodetic Analysis, LLC, 55 Creek Rock Road, Sedona, AZ 86351). He removed a trend using the GPS/Leveling data set as input; therefore, this raster file is a form of a hybrid geoid model distorted only to remove the tilt assumed to be in the NAVD 88. I will refer to this model as Geoid16B_NAD83 to avoid confusion with NGS’ xGeoid16b model.
    Example of Using NGS xGeoid16 Web Tool
    Your input in NAD83 (2011)/GRS80 Ellipsoid:
    Latitude Longitude Ellipsoid Height Station
    38 43 54.95105 79 58 19.75931 599.253 L 275
    Your Result in IGS08/GRS80 Ellipsoid:
    Latitude Longitude Ellipsoid Height
    38 43 54.98136 79 58 19.78679 597.984
    Geoid Model Geoid Height(m) Ortho Height(m) Change in Ortho Height(m)*
    GEOID12B -32.086 630.07 -0.493
    USGG2012 -31.592 629.576 0.001
    xGEOID16A -31.594 629.578 -0.001
    xGEOID16B -31.593 629.577 0
    *Orthometric height difference between xGEOID16B to model shown
    • Step 3: Use the station’s data sheet to identify how the station’s orthometric height was determined; for example, was it rigorously adjusted into the NAVD 88 (published height attribute – Adjusted). We discussed the attributes of the NGS data sheet in Part 5 (February 2016). A summary of the attributes from the NGS data sheet DSDATA.TXT file is provided in the box titled “Extracted from NGS’ DSDATA.TXT.” I have highlighted the most common attributes of the stations involved in making GEOID12B.
    Extracted from NGS’ DSDATA.TXT
    ***************************************************************************
    * dsdata.txt *
    ***************************************************************************
    There are various Vertical Control sources, as specified below:ADJUSTED = Direct Digital Output from Least Squares Adjustment of Precise Leveling.
    (Rounded to 3 decimal places.)ADJ UNCH = Manually Entered (and NOT verified) Output of Least Squares Adjustment of Precise Leveling.
    (Rounded to 3 decimal places.)

    POSTED = Pre-1991 Precise Leveling Adjusted to the NAVD 88 Network After Completion of the NAVD 88 General Adjustment of 1991.
    (Rounded to 3 decimal places.)

    READJUST = Precise Leveling Readjusted as Required by Crustal Motion or Other Cause.
    (Rounded to 2 decimal places.)

    N HEIGHT = Computed from Precise Leveling Connected at Only One Published Bench Mark.
    (Rounded to 2 decimal places.)

    RESET = Reset Computation of Precise Leveling.
    (Rounded to 2 decimal places.)

    COMPUTED = Computed from Precise Leveling Using Non-rigorous Adjustment Technique.
    (Rounded to 2 decimal places.)

    GPSCONLV = Leveled Orthometric Height tied to GPS HT_MOD Orthometric Height.
    (Rounded to 2 decimal places.)

    LEVELING = Precise Leveling Performed by Horizontal Field Party.
    (Rounded to 2 decimal places.)

    H LEVEL = Level between control points not connected to bench mark.
    (Rounded to 1 decimal places.)

    GPS OBS = Computed from GPS Observations.
    (Rounded to 1 decimal places.)

    VERT ANG = Computed from Vertical Angle Observations.
    (Rounded to 1 decimal place; If No Check, to 0 decimal places.)

    SCALED = Scaled from a Topographic Map.
    (Rounded to 0 decimal places.)

    U HEIGHT = Unvalidated height from precise leveling connected at only one NSRS point.
    (Rounded to 2 decimal places.)

    VERTCON = The NAVD 88 height was computed by applying the VERTCON shift value to the NGVD 29 height.
    (Rounded to 0 decimal places.)
    • Step 4: Use the station’s NGS data sheet to determine the adjustment date of the station’s published NAVD 88 orthometric height. We discussed this in Part 7 (June 2016). As mentioned in Part 7, if the station has a different adjustment date than other stations nearby, there could be inconsistencies due to adjustment distribution corrections and/or movement.

    Step 1 was demonstrated in Part 3 (October 2015) so we don’t need to describe the process in this column. Comparing published GEOID12B values with computed values is the first step; the difference is an indication of how well the data fit the model and can be useful for identifying large outliers. It can be helpful in prioritizing where additional observation should be obtained when there are limited resources. Provided below is an example of where to obtain the information for comparing the modeled GEOID12B (N12B) value to the computed GPS/Leveling (h minus H) value using the following formula: Published N12B from the NGS data sheet minus (ellipsoid height from the GPSBM table minus orthometric height from the GPSBM table). The user can obtain the GEOID12B value from the NGS data sheet [see box titled “Excerpt from NGS Data Sheet For Station L 275 (HW2088)”]; for this example, the GEOID12B value for station L 275 is -30.813 m. Table 2 is an excerpt from the GPSBM file that contains the ellipsoid height (599.253 m) and the orthometric height (630.016 m) for station L 275. It should be noted that the ellipsoid and orthometric heights in the GPSBM table are given in millimeters. The first row of table 3 provides the results of the computation: [-30814 mm – (599253 mm – 630016m m) = 51 mm], or 5.1 cm.

    Table 2
    Excerpt of the Excel spreadsheet for GPS on benchmarks (GPSBM) used to make GEOID12B – Stations on plots in this column.
    table2-excerpt-gps-bench-marks

    Excerpt from NGS Data Sheet For Station L 275 (HW2088)
    PROGRAM = datasheet95, VERSION = 8.9.1
    1 National Geodetic Survey, Retrieval Date = OCTOBER 1, 2016
    HW2088 ***********************************************************************
    HW2088 CBN – This is a Cooperative Base Network Control Station.
    HW2088 DESIGNATION – L 275
    HW2088 PID – HW2088
    HW2088 STATE/COUNTY- WV/RANDOLPH
    HW2088 COUNTRY – US
    HW2088 USGS QUAD – MILL CREEK (1995)
    HW2088
    HW2088 *CURRENT SURVEY CONTROL
    HW2088 ______________________________________________________________________
    HW2088* NAD 83(2011) POSITION- 38 43 54.95105(N) 079 58 19.75931(W) ADJUSTED
    HW2088* NAD 83(2011) ELLIP HT- 599.253 (meters) (06/27/12) ADJUSTED
    HW2088* NAD 83(2011) EPOCH – 2010.00
    HW2088* NAVD 88 ORTHO HEIGHT – 630.016 (meters) 2066.98 (feet) ADJUSTED
    HW2088 ______________________________________________________________________
    HW2088 NAD 83(2011) X – 867,581.099 (meters) COMP
    HW2088 NAD 83(2011) Y – -4,906,352.726 (meters) COMP
    HW2088 NAD 83(2011) Z – 3,969,521.039 (meters) COMP
    HW2088 LAPLACE CORR – 0.13 (seconds) DEFLEC12B
    HW2088 GEOID HEIGHT – -30.814 (meters) GEOID12B
    HW2088 DYNAMIC HEIGHT – 629.553 (meters) 2065.46 (feet) COMP
    HW2088 MODELED GRAVITY – 979,873.5 (mgal) NAVD 88
    HW2088
    HW2088 VERT ORDER – FIRST CLASS II
    HW2088
    HW2088 Network accuracy estimates per FGDC Geospatial Positioning Accuracy
    HW2088 Standards:
    HW2088 FGDC (95% conf, cm) Standard deviation (cm) CorrNE
    HW2088 Horiz Ellip SD_N SD_E SD_h (unitless)
    HW2088 ——————————————————————-
    HW2088 NETWORK 1.00 1.94 0.45 0.36 0.99 -0.05669181

    Table 3 contains the comparisons between modeled geoid values and their computed geoid values for five station pairs that have large relative differences. Looking at table 3 one can see that there are several large relative differences between the published GEOID12B model and computed geoid model (see column titled “N12B minus (h-H)” in table 3). This doesn’t mean that the model is incorrect, it only means that there were large relative differences that the model had to account for. As previously mentioned, GEOID12B was created to be consistent with the NAVD 88.

    Since the experimental geoid model xGeoid16b_NAD is not distorted to conform to the NAVD 88 everywhere, it should provide better information for identifying outliers and determining which stations appear to be inconsistent with its neighbors.

    Figure 1 - All GPS on BMS Residuals Using Geoid16b_NAD model (note: rejections by geoid team have been removed).
    Figure 1 – All GPS on BMS Residuals Using Geoid16b_NAD model (note: rejections by geoid team have been removed).

    Table 3
    Table of selected stations involving large relative differences depicted in plots in this column.
    (Results are provided for GEOID12B and Geoid16B_NAD Models*)
    *Michael Dennis, a Ph.D. candidate at Oregon State University, created the xGEOID16B ArcGIS raster, where the model has been referenced to NAD 83 with a trend and bias added to account for the apparent tilt in the NAVD 88. This model is denoted as Geoid16B_NAD (N16b) in this column.

    table3-excerpt-gps-bench-marks

    Figure 1 is a plot of all of the GPSBM residuals using the Geoid16B_NAD83 model. This plot indicates that there are a lot of large residuals. First, let’s define what I’m calling residuals. The residuals on my plots are the differences between the modeled geoid height value and the computed geoid height value using the ellipsoid height (h) and orthometric height (H) from the GPSBM data set; that is, residual = modeled gravity value – (h minus H). The largest negative residual is -37.3 cm and the largest positive residual is 33.8 cm.

    image012
    Figure 2 – Positive GPS on BMS Residuals Using Geoid16b_NAD model (note: rejections by geoid team have been removed).

    Figure 2 is a plot of the positive GPS on BMS residuals using Geoid16b_NAD geoid model. There are 5957 residuals greater than 5 cm (not including the stations rejected by the NGS geoid team). As you can see, it appears that most of the positive residuals are on the eastern half of the United States.

    Figure 3 - Negative GPS on BMS Residuals Using Geoid16b_NAD model (note: rejections by geoid team have been removed).
    Figure 3 – Negative GPS on BMS Residuals Using Geoid16b_NAD model (note: rejections by geoid team have been removed).

    Figure 3 is a plot of the negative GPS on BMS residuals using Geoid16b_NAD geoid model. There are 4113 residuals less than -5 cm (not including the stations rejected by the NGS geoid team). As you can see from the plot, the negative residuals appear to be more evenly distributed across the United States than the positive residuals. It does, however, appear that there are more negative residuals greater than -5 cm along the Gulf Coast, Atlantic Coast, and the Great Lakes than there are positive residuals greater than 5 cm. In addition, there appears to be a lot of negative residuals in the northeastern United States.

    image016
    Figure 4 – GPS on BMS Residuals Using Geoid16b_NAD model in North Carolina and South Carolina (note: rejections by geoid team have been removed).

    Figure 4 is a plot of the GPS on BMS residuals using the Geoid16b_NAD geoid model in the North Carolina and South Carolina border region. What’s interesting about this plot is that South Carolina doesn’t seem to have many negative residuals where North Carolina has both negative and positive residuals. We will look at this in more detail later in this column.

    image018
    Figure 5 – GPS on BMS Residuals Using Geoid16b_NAD model in Washington and Oregon Region (note: rejections by geoid team have been removed).

    Figure 5 is a plot of the GPS on BMS residuals using Geoid16b_NAD model in the Washington and Oregon Region. This graphic shows some large grouping of negative and positive residuals, especially along the Pacific Coast in Northwestern Washington State.

    Now, let’s look at some large relative differences in residuals between stations that are spatially close together. Figure 6 is a plot of large relative differences between groups of GPS on BMS residuals (using Geoid16b_NAD model) at the North Carolina/South Carolina border. In figure 6, two stations (FA1337 and FA1560) are about 20 km apart and the difference in residuals is -18.6 cm (-12.4 cm minus 6.2 cm). This is a large difference for only 20 km. What is even more significant is that the group of stations near FA1337 are all negative residuals (around -10 cm) and the group of stations near FA1560 are all positive residuals (around 6 cm), this could be an indication of a large distribution correction due to the NAVD 88 design. We discussed the distribution correction in Part 7 (June 2016). These stations definitely needs to be investigated.

    The next step in my process is to look at the NGS data sheets for these stations to determine how the stations were adjusted.

    Step 3: Look at the station’s data sheet to identify how the station’s orthometric height was determined; for example, was it rigorously adjusted into the NAVD 88 (published height attribute is “Adjusted”) or was it determined by precise leveling performed by horizontal field party (published height attribute is “Leveling”).

    The data sheet for station FA1337 states that the NAVD 88 attribute code is “GPS OBS.” [See box titled “Excerpt from NGS Data Sheet for PID FA1337.”] The data sheet for FA1560 states that the NAVD 88 attribute code is “Adjusted.” The orthometric height on the GPSBM file is different than the current published NAVD 88 orthometric height for station FA1337 (See table 3). This station’s leveling-derived orthometric height was superseded by a GNSS-derived orthometric height. Saying that, the GPSBM file only uses leveling-derived orthometric heights; therefore, stations that have been superseded by GNSS surveys are still included in the GPSBM file but their original published leveling-derived height is used for the analysis. Table 3 provides the orthometric height for FA1337 that was used in making GEOID12B. As previously mentioned, stations may be rejected by the geoid team based on the criteria outlined in the beginning of this column. Saying that, neither of the two stations were rejected by the NGS geoid team. This implies that the stations were consistent with their neighbors as far as the geoid model was concerned. Figure 6 confirms that all the stations around FA1337 and FA1560 are consistent with each other based on the Geoid16b_NAD geoid model. The fact that the two groups differ by 18 6 cm needs to be investigated.

    Excerpt from NGS Data Sheet for PID FA1337
    PROGRAM = datasheet95, VERSION = 8.9.1
    1 National Geodetic Survey, Retrieval Date = OCTOBER 3, 2016
    FA1337 ***********************************************************************
    FA1337 HT_MOD – This is a Height Modernization Survey Station.
    FA1337 DESIGNATION – RU 36
    FA1337 PID – FA1337
    FA1337 STATE/COUNTY- NC/RUTHERFORD
    FA1337 COUNTRY – US
    FA1337 USGS QUAD – FOREST CITY (1993)
    FA1337
    FA1337 *CURRENT SURVEY CONTROL
    FA1337 ______________________________________________________________________
    FA1337* NAD 83(2011) POSITION- 35 18 08.14237(N) 081 51 17.93516(W) ADJUSTED
    FA1337* NAD 83(2011) ELLIP HT- 249.869 (meters) (06/27/12) ADJUSTED
    FA1337* NAD 83(2011) EPOCH – 2010.00
    FA1337* NAVD 88 ORTHO HEIGHT – 281.79 (meters) 924.5 (feet) GPS OBS
    FA1337 ______________________________________________________________________
    Figure 6 - GPS on BMS Residuals: Large Relative Differences Between a Group of Stations at the North Carolina/South Carolina Border (note: rejections by geoid team have been removed)
    Figure 6 – GPS on BMS Residuals: Large Relative Differences Between a Group of Stations at the North Carolina/South Carolina Border (note: rejections by geoid team have been removed)

    Figure 7 is a plot of the GPS on BMS residuals using Geoid16b_NAD that depicts a large difference between two stations only 20 km apart near the Maryland/West Virginia border. I will use this station pair to demonstrate the next step in my process.

    Step 4 is to use the station’s NGS data sheet to determine the adjustment date the of station’s published NAVD 88 orthometric height.

    The NAVD 88 attribute on the NGS data sheet states that both of these stations are coded as “Adjusted” but station JW0639 adjustment date is April 1995 (see box titled “excerpt from NGS Data Sheet for PID JW0639”) and JW1296 adjustment date was in June 1991 (the General Adjustment of NAVD 88). These large relative differences could be due to inconsistencies between adjusted heights due to the adjustment distribution corrections and/or constraints imposed in the April 1995 adjustment. Bench marks near the stations should be observed to determine if the same large relative difference exists, and the 1995 NAVD 88 adjustment project report should be reviewed to determine if a large distribution correction was applied.

    Excerpt from NGS Data Sheet for PID JW0639
    1 National Geodetic Survey, Retrieval Date = OCTOBER 3, 2016
    JW0639 ***********************************************************************
    JW0639 CBN – This is a Cooperative Base Network Control Station.
    JW0639 DESIGNATION – J 17 RESET
    JW0639 PID – JW0639
    JW0639 STATE/COUNTY- MD/GARRETT
    JW0639 COUNTRY – US
    JW0639 USGS QUAD – ACCIDENT (1994)
    JW0639
    JW0639 *CURRENT SURVEY CONTROL
    JW0639 ______________________________________________________________________
    JW0639* NAD 83(2011) POSITION- 39 37 53.59739(N) 079 18 57.44776(W) ADJUSTED
    JW0639* NAD 83(2011) ELLIP HT- 701.266 (meters) (06/27/12) ADJUSTED
    JW0639* NAD 83(2011) EPOCH – 2010.00
    JW0639* NAVD 88 ORTHO HEIGHT – 732.713 (meters) 2403.91 (feet) ADJUSTED
    JW0639 ______________________________________________________________________
    *
    *
    *
    JW0639
    JW0639.The orthometric height was determined by differential leveling and
    JW0639.adjusted by the NATIONAL GEODETIC SURVEY
    JW0639.in April 1995.
    JW0639
    Figure 7 – GPS on BMS Residuals Using Geoid16b_NAD: Large Relative Difference Between Stations About 20 km Apart Along MD/WV Border (note: rejections by geoid team have been removed).
    Figure 7 – GPS on BMS Residuals Using Geoid16b_NAD: Large Relative Difference Between Stations About 20 km Apart Along MD/WV Border (note: rejections by geoid team have been removed).
    Figure 8 – GPS on BMS Residuals Using Geoid16b_NAD: Large relative Difference Between Stations 15 km Apart in Randolph County, West Virginia (note: rejections by geoid team have been removed).
    Figure 8 – GPS on BMS Residuals Using Geoid16b_NAD: Large relative Difference Between Stations 15 km Apart in Randolph County, West Virginia (note: rejections by geoid team have been removed).

    Figure 8 is a plot of GPS on BMS residuals using Geoid16b_NAD that depicts a large relative difference between stations 15 km apart in Randolph County, West Virginia. This plot involves station HW3677 which has a published NAVD 88 attribute of “Leveling.” (See box titled “Excerpt from NGS Data Sheet for PID HW3677.”) The excerpt from the data sheet has the following statement: “The orthometric height was determined by differential leveling. The vertical network tie was performed by a horz. field party for horz. obs reductions. Reset procedures were used to establish the elevation.”

    It would be useful if stations near this station were observed by GNSS surveys to determine what is occurring in this region.

    Excerpt from NGS Data Sheet for PID HW3677
    1 National Geodetic Survey, Retrieval Date = OCTOBER 2, 2016
    HW3677 ***********************************************************************
    HW3677 DESIGNATION – GPS 1
    HW3677 PID – HW3677
    HW3677 STATE/COUNTY- WV/RANDOLPH
    HW3677 COUNTRY – US
    HW3677 USGS QUAD – MILL CREEK (1995)
    HW3677
    HW3677 *CURRENT SURVEY CONTROL
    HW3677 ______________________________________________________________________
    HW3677* NAD 83(2011) POSITION- 38 37 50.21531(N) 079 55 29.64175(W) ADJUSTED
    HW3677* NAD 83(2011) ELLIP HT- 1129.355 (meters) (06/27/12) ADJUSTED
    HW3677* NAD 83(2011) EPOCH – 2010.00
    HW3677* NAVD 88 ORTHO HEIGHT – 1159.91 (meters) 3805.5 (feet) LEVELING
    HW3677 ______________________________________________________________________
    *
    *
    *
    *
    HW3677
    HW3677.The orthometric height was determined by differential leveling.
    HW3677.The vertical network tie was performed by a horz. field party for horz.
    HW3677.obs reductions. Reset procedures were used to establish the elevation.
    HW3677

    Figure 9 is a GPS on BMS residual plot of large relative stations about 30 km apart in Wasco County, Oregon. This plot has two stations with large differences and both stations have the NAVD 88 attribute of “Adjusted.” Their NGS data sheet states that they were both established in the general adjustment of NAVD 88 in June 1991. In this particular case, the leveling in this region is very old. As described in Part 7 (June 2016), you can retrieve all project identifiers for those projects with observations to or from a station using the station’s PID. The output from the NGS Data Sheet Mark Source Routine for PID RC1228 is shown in the box titled “Output from NGS Data Sheet Mark Source Routine.”

    Output from NGS Data Sheet Mark Source Routine
    Program: mark_sources Version: 3.0 Date: May 1, 2013RC1228OR/065 J 108
    ———————————————————-
    GPS_OBS
    ———–
    GPS_OBS FORE_POINT in GPS1655
    DIR_OBS
    ———–
    DIST_OBS
    ———–
    VERT_OBS
    ———–
    LEV_OBS
    ———–
    LEVEL_OBS
    ———–
    LEVEL_OBS STAND_POINT in L3410
    LEVEL_OBS FORE_POINT in L3410***********************************************************
    Figure 9 – GPS on BMS Residuals Using Geoid16b_NAD: Large relative stations about 30 km apart in Wasco County, Oregon (note: rejections by geoid team have been removed).
    Figure 9 – GPS on BMS Residuals Using Geoid16b_NAD: Large relative stations about 30 km apart in Wasco County, Oregon (note: rejections by geoid team have been removed).

    Figure 9 is a GPS on BMS residual plot of large relative stations about 30 km apart in Wasco County, Oregon. This plot has two stations with large differences and both stations have the NAVD 88 attribute of “Adjusted.” Their NGS data sheet states that they were both established in the general adjustment of NAVD 88 in June 1991. In this particular case, the leveling in this region is very old. As described in Part 7 (June 2016), you can retrieve all project identifiers for those projects with observations to or from a station using the station’s PID. The output from the NGS Data Sheet Mark Source Routine for PID RC1228 is shown in the box titled “Output from NGS Data Sheet Mark Source Routine.”

    Excerpt from NGS Data Sheet for PID RC1228

    PROGRAM = datasheet95, VERSION = 8.9.1
    1 National Geodetic Survey, Retrieval Date = OCTOBER 2, 2016
    RC1228 ***********************************************************************
    RC1228 DESIGNATION – J 108
    RC1228 PID – RC1228
    RC1228 STATE/COUNTY- OR/WASCO
    RC1228 COUNTRY – US
    RC1228 USGS QUAD – WAPINITIA (1996)
    RC1228
    RC1228 *CURRENT SURVEY CONTROL
    RC1228 ______________________________________________________________________
    RC1228* NAD 83(2011) POSITION- 45 06 49.69715(N) 121 19 19.81396(W) ADJUSTED
    RC1228* NAD 83(2011) ELLIP HT- 624.596 (meters) (06/27/12) ADJUSTED
    RC1228* NAD 83(2011) EPOCH – 2010.00
    RC1228* NAVD 88 ORTHO HEIGHT – 646.140 (meters) 2119.88 (feet) ADJUSTED
    RC1228 ______________________________________________________________________
    *
    *
    *
    RC1228
    RC1228 HISTORY – Date Condition Report By
    RC1228 HISTORY – 1934 MONUMENTED CGS
    RC1228 HISTORY – 1985 MARK NOT FOUND USPSQD
    RC1228 HISTORY – 1985 MARK NOT FOUND USPSQD
    RC1228 HISTORY – 20001010 GOOD OR-065
    Figure 10 – GPS on BMS Residuals Using Geoid16b_NAD: Large relative Differences between Stations along the Oregon/Washington Border (note: rejections by geoid team have been removed).
    Figure 10 – GPS on BMS Residuals Using Geoid16b_NAD: Large relative Differences between Stations along the Oregon/Washington Border (note: rejections by geoid team have been removed).

    Figure 10 is a plot of GPS on BMS residuals using Geoid16b_NAD depicting large relative differences between stations along the Oregon/Washington State border. It is the near Puget Island along the Columbia River. Station SC0330 and SC1086 are only 7 km apart and the relative difference is -20 cm (-11.4 cm minus 8.6 cm). This could be an issue with the NAVD 88 network design because there doesn’t appear to be many river crossing along the river between border stations. The fact that the residuals on the Washington State side are negative and the Oregon State side are positive is an indication that the stations need to be investigated.

    Figure 11 – GPS on BMS Residuals Using Geoid16b_NAD: Large Negative Residuals North of Border between Oregon and Washington and Positive (or Small Negative) Residuals South of Border (note: rejections by geoid team have been removed).
    Figure 11 – GPS on BMS Residuals Using Geoid16b_NAD: Large Negative Residuals North of Border between Oregon and Washington and Positive (or Small Negative) Residuals South of Border (note: rejections by geoid team have been removed).

    The last figure, figure 11, is a plot of the GPS on BMS residuals using Geoid16b_NAD model that depicts large negative residuals north of the border between Oregon and Washington and positive (or small negative) residuals south of the border. This plot shows that the northern side of the river has large negative residuals all the way to the Pacific Coast. Once again, this is an indication that this portion of the NAVD 88 network should be investigated.

    This column has focused on analyzing NGS’ GPS on BM data set that is used to make NGS’ hybrid geoid models. It provided procedures that users could employ when analyzing the differences between the modeled geoid values and the computed geoid values using GPS/Leveling data. This GPSBM data set or one similar will be used to make the next hybrid geoid model, as well as provide input to the transformation model between NAVD 88 and the new 2022 Vertical Reference System. All geospatial users should help develop this GPS on BMS data set to help improve the National Spatial Reference System and future hybrid geoid models. This column provided several examples of large relative differences in residuals between neighboring stations. Each example represents stations that should investigated based on different reasons, such as a weak NAVD 88 leveling network design in the region, the station’s published height attribute code implies that the station was not rigorously adjusted into the NAVD 88, and station pairs have different adjustment dates indicating a possible adjustment distribution correction issue or movement.

    NGS has a program called “GPS on Bench Mark” to support users that occupy bench marks with GNSS equipment. This web site contains a lot of good information and provides the users with methods to recover, observe, and report information about stations in NGS’ database. The write up from the webpage is given below. I have highlighted a few sentences that the reader may find useful.

     

    Write up from: GPS on Bench Marks?

    What is GPS on Bench Marks?

    Improve the National Spatial Reference System (NSRS):

    Recover: Look up the description of an existing bench mark and visit the bench mark of your choice.
    Observe: Record field notes, take digital photos, and collect GPS observations or coordinates for the bench mark you visit.
    Report: Use online tools to send the information to NGS.

    Where?

    Currently there are over 400,000 bench marks across the Conterminous United States (CONUS), Alaska, Hawaii and all U.S. territories. Tidal marks and bench marks are used for determining heights. Use the maps to prioritize which bench marks to observe.

    Who can participate?

    Anyone with Global Positioning System (GPS) enabled phones, hand held devices or survey-grade GPS receivers can participate. Recommended procedures vary depending on the type of equipment used.

    When should I start?

    You can collect and share information any time. Join volunteer efforts across the United States in celebration of National Surveyors Week beginning March 20, 2016. Contact the local National Society of Professional Surveyors chapter or your NGS geodetic advisor to learn about projects being planned in your local area.

    How?

    For specific information on how to help please visit the Recover, Observe, and Report web pages that have instructions. Other resources include “Hunting for Marks!” and Geocaching Benchmark Hunting.

    Why does this matter?

    By providing GPS on benchmarks today you can help NGS improve the next hybrid geoid model, increasing access to NAVD 88, and enabling conversions to the new vertical datum in 2022.

    You can also help the local surveying community know about nearby marks by improving scaled horizontal positions and updating the mark condition or description by submitting a mark recovery.

    What happens next?

    NGS will use your data to update its databases and improve future models and tools. If you still have questions, contact the GPS on BM Team.

    In addition to participating in the NGS’ GPS on Bench Mark program, all geospatial users should participate in NGS’ 2017 geospatial summit, which will be held in April in Silver Spring, Maryland.

    This summit is an opportunity for all users of the National Spatial Reference System (NSRS) to obtain a better understanding of NGS’ plans to modernize the NSRS. Users will be able to provide feedback directly to NGS leadership. My next column will address NGS plans to replace the North American Vertical Datum of 1988 in 2022.

  • Discover your inner GPS

    Discover your inner GPS

    O’Keefe (left). Grid cells form networks with the place cells in the hippocampus, a circuitry that creates a comprehensive positioning system — an inner GPS — in the brain. (Source: Nobel Committee)
    O’Keefe (left). Grid cells form networks with the place cells in the hippocampus, a circuitry that creates a comprehensive positioning system — an inner GPS — in the brain.(Source: Nobel Committee)

    The Institute of Navigation Satellite Division looked deeply inward for its keynote speaker at this year’s ION GNSS+ conference, held Sept. 12–16 in Portland, Oregon.

    Nobel Laureate John O’Keefe provided insight into how our brains determine position. In 1971, O’Keefe recorded signals from individual nerve cells in the hippocampus of rats roaming about a room. He found that a type of nerve cell in the hippocampus was always activated when a rat was at a certain place, and other nerve cells were activated when the rat was at other places.

    O’Keefe concluded that these “place cells” formed a map of the room. The place cells were not just registering visual input, but building an inner map of the environment. The hippocampus generates numerous maps, which can be seen by the activity of place cells activated in different environments. The memory of an environment can be stored as a specific combination of place-cell activities in the hippocampus.

    In 2005, co-laureates May-Britt and Edvard Moser discovered another key component of the brain’s positioning system. “Grid cells” generate a coordinate system and allow for precise positioning and pathfinding. Their research showed how place and grid cells make it possible for rats — and presumably us — to find our way around, determining where we are in the world and which way to go.

    Recent investigations show that place and grid cells also exist in humans. In patients with Alzheimer’s disease, the hippocampus is frequently affected, causing those afflicted to lose their way. Knowledge about the brain’s positioning system may help us understand the mechanism underpinning the disease.

  • Portrait of Galileo: European groups say constellation is ready for service

    galileo-programme-update-ion-2016-vf1
    From a Galileo programme update presented at ION GNSS+ 2016.

    Spokespersons from the European Commission, the European Space Agency and the European GNSS Agency (GSA) built a portrait of Galileo at the ION GNNS+ conference of a satellite constellation ready to step upon the world stage. Meanwhile, four new satellites are scheduled to launch aboard a single Ariane rocket on Nov. 17, leading to declaration of initial services by the end of the year.

    With 14 satellites in orbit, 12 ordered and four on the launchpad, system operators feel confident in predicting initial operational capability by the end of this year. They already have their eyes set on additional service distinctions driven by emerging new requirement from user communities:

    • Authentication, for applications requiring trusted position and timing information; a key feature to enable new types of commercial applications such as pay-as-you-drive car insurance, road user charging (highway tolling) and access to mobile content
    • A robust timing service
    • Advanced receiver autonomous integrity monitoring (ARAIM)
    • Emergency warning services
    • A Galileo regional service
    • Ionosphere prediction service
    • SBAS authentication

    Key areas identified to drive Galileo evolution included timing for 5G telecoms, digital video broadcasting and autonomous vehicles.

    GNSS will increasingly be used not as a sole localization solution but deeply integrated with several positioning networks and sensors to work across an array of contexts, according to the several European experts. However, despite growing alternative solutions, GNSS will remain core as the most cost-effective global positioning technology, especially for outdoor location information and larger scale applications.

    Looking at the future, for the majority of mass-market applications, an accuracy of a few meters is sufficient, but key strategic users will need (some already need) better performance that must be satisfied. Galileo evolution has to offer enhanced performance, enabling new and strategic applications, to remain at the center of the positioning and timing market.

    Galileo’s evolutionary targets to improve in the future were listed as: a ranging accuracy between 2 and 5 times that to be declared at Galileo FOC (in 2020?); position accuracy down to sub-meter level; timing accuracy increased by two times over Galileo FOC; better support of spoofed users; enhanced authentication (nav message authentication) and anti-replay.

    New Operations Center in Spain. The European GNSS Agency (GSA) is gearing up to assume its operational role for Galileo in early 2017. During the summer the GSA formally accepted their Loyola de Palacio facility in Madrid, Spain that houses the European GNSS Service Centre (GSC).

    GSA already oversees the operation and service provision for the European Geostationary Navigation Overlay Service (EGNOS) (since 2015) along with managing the security accreditation and general security provision for both programmes.

    Since 2013, the core team at GSC has been providing limited services and working as a precursor to GSC v1. Its key work includes supporting the lead-up to Galileo Initial Services provision, along with operating the GSC Helpdesk, disseminating orbital products to the Search and Rescue (SAR) community, supporting GNSS-related research and industrial activity and monitoring user satisfaction. Once operational, GSC v1 will be connected to the Galileo core system, thus enabling the long anticipated Commercial Service. This service is expected to enter operations by mid-2017.

    Galileo Hackathon in Berlin. The GSA invites coders, app developers and other interested parties to a two-day event in early November, the Galileo Hackathon. “Be one of the first to use Galileo!” The online invitation seeks those who want to shape the future of Location-Based Services (LBS) and Geo-IoT to become pioneer developers, showcase their skills, connect with the Geo-IoT app-dev community, and win prizes. November 3–4 in Berlin.

  • Galileo Initial Services looming

    With Galileo Initial Services at last on the horizon and a quadruple satellite launch scheduled for November, here’s hoping that Europe’s GNSS constellation will be delivering limited, but reliable, global PNT services before the year is out.

    The four Galileo satellites for Arianespace’s first Ariane 5 mission for the constellation are being prepared at ESA’s launch facility in French Guiana. The flight is scheduled for 17 November. However neither these four new satellites, nor the two orbited in May, are required to deliver Galileo Initial Services, which should be launched officially some time in November. Fingers crossed.

    The European GNSS Agency (GSA) is gearing up to assume its operational role for Galileo in early 2017. During the summer the GSA formally accepted their Loyola de Palacio facility in Madrid, Spain that houses the European GNSS Service Centre (GSC). This is a significant milestone in the development of the programme and its service provision as Galileo’s “door to the GNSS world” as GSA Executive Director Carlo des Dorides described the facility at the handover ceremony.

    GSA already oversees the operation and service provision for the European Geostationary Navigation Overlay Service (EGNOS) (since 2015) along with managing the security accreditation and general security provision for both programmes.

    The GSC offers over 1,100 square metres of space and currently employs over 40 people. Since 2013, the core team at GSC has been providing limited services and working as a precursor to GSC v1. Its key work includes supporting the lead up to Galileo Initial Services provision, along with operating the GSC Helpdesk, disseminating orbital products to the Search and Rescue (SAR) community, supporting GNSS-related research and industrial activity and monitoring user satisfaction. Once operational, GSC v1 will be connected to the Galileo core system, thus enabling the long anticipated Commercial Service. This service is expected to enter operations by mid-2017.

    Once the Galileo Operations Contract is awarded and Initial Services officially declared, the GSC is expected to see a significant increase in staff.

    Also in the summer CNES President and France’s inter-ministerial coordinator for European satellite navigation programmes Jean-Yves Le Gall was elected as the new chair of the GSA Administrative Board with Mark Bacon, representing the United Kingdom, elected as deputy chair.

    “I am honoured to have been elected chair of the GSA Administrative Board, with Galileo now poised to enter its operational phase,” said Le Gall. “This election confirms the desire of Member States to join forces on the cusp of a prolific period for European space as we move Galileo towards full operational capability.”

    Brexit blues?

    Mark Bacon added “I am very pleased to have been elected to work with the Board and I look forward to helping the GSA deliver on the Galileo and EGNOS programmes over the coming years.”  However the UK’s decision to leave the EU (Brexit) must make his position rather uncomfortable – and temporary – to say the least.

    The GSA Administrative Board is composed of representatives from each EU Member State, the European Commission, and the EU parliament. The Board meets three times per year to ensure that the Agency performs its tasks correctly. As things stand if the UK is no longer an EU Member State it must lose its representative(s) on the advisory board.

    However, the relationship between the UK and EU space programmes is, of course, subject to the Brexit negotiations. The UK will almost certainly remain a member of the European Space Agency (ESA) as this is a pan-European body not an EU agency, however when it leaves the EU the country will have to renegotiate terms if it wants to continue to participate in the key EU programmes such as Galileo GNSS and Copernicus Earth Observation system.

    The ESA is autonomous from the EU and should not be directly affected by Brexit confirmed Jean Bruston, head of ESA’s EU policy office at a media briefing in mid-September. But “As soon as it [Britain] is leaving the EU it is not participating in these programmes [Galileo / Copernicus] any longer,” he observed.

    In addition, UK-based companies hold contracts worth tens of millions of euros from ESA to supply hardware for the Copernicus and Galileo GNSS. “If nothing changes [and Brexit goes ahead], we would have to stop these contracts,” said Bruston bluntly.

    Of course, Britain could still contribute to Galileo and Copernicus if it negotiated a third-party agreement with the EU, as Norway and Switzerland (both non EU members) have done. The down side is that this may take some time to initiate, let alone complete, and if Britain sticks to its guns on issues such as free movement of people then the likelihood of a successful outcome for the UK is not high.

    In an interview with French media ESA director-general Jan Woerner reinforced Bruston’s views saying that “the UK will remain a member state of ESA, this is very clear” but also continuing “As we are also dealing with European programmes like Copernicus and Galileo, and also the question of UK citizens working on the continent and all these legal issues, we have to take this into account.”

    EU opportunity

    Many in ‘continental Europe’, as we Brits so often condescend to describe our fellow Europeans, will be more than happy to see the U.K. no longer participating in deciding key aspects of EU space and other policy areas.

    It is no coincidence that the European Commission has become much more vocal on plans for a European defence force since the Brits announced their departure. The U.K. has long been opposed to the concept of an ‘EU Army.’ However planning and military cooperation between Member States outside normal NATO channels has been increasing over many years. The small and discreet (so discreet that I didn’t realise the exact location of its HQ in Brussels until the recent terrorist incidents meant burly Belgian paratroopers were stationed outside and I asked them what they were guarding. Has to be said they were not discreet!) has seen its budget frozen for the last five years, but this may now change.

    The interface of EU space and defence policy – in particular ‘dual use’ issues – will also become simpler without the U.K.’s protests. A leaked draft of the upcoming EU Space Policy communication talked directly of dual-use synergies to reinforce security from space, in particular to reduce costs and improve efficiency, and that the next generation of EU GNSS and Copernicus programmes should be designed from the start to be more relevant for security purposes. Defence-related research is also slated for future Horizon 2020 calls.

    The draft policy document also underlines that with EU space programmes becoming fully operational, building stability, trust and confidence in users is a key objective. Current services must be fully deployed and their long-term continuity and evolution assured. This continuity should be driven by user needs and take into consideration the mid-term (hardly mid-term for Galileo!) evaluation of the programmes that should happen in 2017. For Galileo and EGNOS, the document looks to improvements in the current services, including greater robustness and performance, and provision of additional services, such as regional or timing services.

    California dreaming

    So with Brexit what is the U.K.’s GNSS – and space-related – industry and research community to do? Of course many of the UK industrial players are multi-national companies and internal transfer of people and/ or projects will overcome many issues. And bi-lateral collaborative agreements on exchange of talent and ideas between partners can also achieve the same results for smaller companies and research groups. However not having a seat in the policy process and the development of programmes will put ‘UK plc’ at a distinct disadvantage in my opinion.

    But U.K. leaders say that Brexit is an opportunity to be seized and that the U.K. should be looking to sell  goods and services in other global markets than the EU. Which is something most U.K. industry has been doing since trade/ time began. And in my experience U.K. business leaders have always been much more eager to go jump on a plane to the States or Australia than go visit their European neighbours – something to do with our renowned national language skills perhaps?

    Space is no exception – and one that has been shown to be a success in recent times. A helping hand is provided by InnovateUK, the U.K.’s government innovation agency, that is organising its third ‘Space Mission UK’ to the US in November. These are trade and investment missions specifically designed to support U.K. start-up companies to build world-leading space and satellite application businesses.

    Space Mission 1 visited Utah, LA and Silicon Valley in August 2015 and Space Mission 2 landed in Houston in November 2015. Space Mission 3 will visit San Francisco and LA from 5-11 November this year.

    Mission programmes are varied but typically include visits to companies working at the forefront of the sector, networking opportunities with investors and corporate venture people interested in space, visits to incubators, accelerators and technology hubs, and masterclasses on pitch development, business culture and market entry.

    The previous two Space Missions have had immediate impact for the companies involved, including securing over £1 million in investment, and initiating collaborations with major organisations such as NASA and (ironically) ESA, and winning contracts with the UK Ministry of Defence at home.

    GNSS-related companies in previous missions include Arralis who build high-end semiconductor chips but have also been funded to develop novel GNSS antennas, and an exciting data fusion start-up – Gyana – that takes complex inputs from multiple data sources, including satellite, to build simple to understand 3D situational images. The founder of the business, engineering graduate Joyeeta Das, has raised US $1.1m since the mission.

    You can find a complete list of companies who have participated on the previous missions here.

    The selection for Space Mission 3 has closed and I am told there is at least one GNSS applications company that has been chosen to be on the plane in November. Good luck to them all!

    Google emergency LBS upgrade

    E112 is a location-based version of the 112 universal European emergency number, where the telecommunication operator transmits location information to the emergency centre in parallel to the call itself. With more than 70 percent of calls to emergency services coming from mobile phones, getting help fast and efficiently to the caller can be challenging if they don’t know where they are. Now, in a major step forward for implementation, Google has created and rolled out in two European countries (U.K. and Estonia) its Emergency Location Service on Android, with other regions to follow. The feature, when supported by the caller’s network, sends the phone’s location to emergency services when the 112 (or equivalent) emergency number is dialed.

    Emergency Location Service is supported by more than 99 percent of existing Android devices (version 2.3 and above) through Google Play services. The service activates when supported by the mobile network operator or emergency infrastructure provider.

    The new geographical location system claims to identify the source of a mobile phone emergency call to typically within 0.003 square kilometres (less than half the size of a football field) instead of a current average of around 12 square kilometres.

    When an emergency call is made with an enabled Android smartphone, the phone automatically activates its location service and sends its position by text message to the 112 service. This usually takes less than 20 seconds. This text message is not visible on the handset and is not charged for.

    And the first European Galileo-ready smartphone has been launched with the Aquaris X5 Plus smartphone, produced by the Spanish technology company BQ, and based on the Galileo-supported Qualcomm Snapdragon 652 processor with Galileo capability accessible via a software update to be released in Quarter 4 2016.

    U.S.-based Qualcomm announced in June that it was adding support for Galileo across its Snapdragon processor and modern portfolios for smartphone, computing, automotive and IoT applications.

    As well as Galileo capability, the Aquaris X5 Plus is powered by the latest Google Android OS and has all the usual features of a top end smart phone including 16 mega pixel ‘back’ camera and support for 4k video recording with a stabiliser and fingerprint recognition for added security.

    If you want to take the pulse of the GNSS user technology industry and keep up with the latest trends then you’ll need to get your hands on the GSA’s GNSS User Technology Report due out at the beginning of October.

    The 2016 report will be launched on 4 October as part of the Horizon 2020 Space Information Days in Prague. This two-day GSA-hosted event will introduce the third call for GSA-funded Horizon 2020 research and innovation proposals for Galileo and EGNOS.

    The document will take an in-depth look at the latest state-of-the-art GNSS receiver technology, along with providing expert analysis on the various trends that are defining the future global GNSS technology landscape. The report will focus on three key areas: mass market solutions; transport safety and liability-critical solutions; and high precision, timing and asset management solutions.

    Pulsar GNSS for deep space

    The use of pulsars, highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation with a very precise period, have been potential candidates for a deep space navigation system for many years. Now a paper from the U.K.’s National Physical Laboratory (NPL) and the University of Leicester shows that pulsars can be used to obtain position along a particular direction in space to an accuracy of two kilometres in the direction of the pulsar. Furthermore such a technology could operate autonomously and greatly increase the number and capabilities of space missions, the paper claims.

    To calculate their position a space craft would need to carry a small X-ray telescope. The method uses X-rays emitted from pulsars, which can be used to work out the position of a craft in space in 3 dimensions to an accuracy of 30 km at the distance of Neptune. Certain types of pulsar, called ‘millisecond pulsars’, emit pulses of radiation with the regularity and precision of an atomic clock and therefore could be used much like GNSNS in space.

    The paper, published in Experimental Astronomy[1], details simulations undertaken using data, such as the pulsar positions and a craft’s distance from the Sun, for an ESA feasibility study of the concept. The simulations took these data and tested the concept of triangulation by pulsars with current X-ray telescope technology and state-of-the art position, velocity and timing analysis. This generated a list of usable pulsars and measurements of how accurately a small telescope can lock onto these pulsars and calculate a location.

    The key finding was that at a distance of 30 astronomical units – the approximate distance of Neptune from the Earth – an accuracy of 2km or 5km can be calculated in the direction of a particular pulsar (PSR B1937+21) by locking onto the pulsar for ten or one hours respectively and that by locking onto three pulsars, a 3D location with an accuracy of 30km can be calculated.

    This is an improvement on the current navigation methods of the ground-based Deep Space Network (DSN) and European Space Tracking (ESTRACK) network as it could be autonomous with no need for Earth contact for months or years, if an advanced atomic clock is also on the craft. Also ESTRACK and DSN can only track a small number of spacecraft at any one time. It is also possible that the pulsar technique could be quicker.

    Dr Setnam Shemar from NPL commented: “How these [space]craft navigate will in future become a limiting factor to our ambitions. The cost of maintaining current large ground-based communications systems based on radio waves is high and they can only communicate with a small number of craft at a time. Using pulsars as location beacons in space, together with a space atomic clock, allows for autonomy and greater capability in the outer solar system.”

    This simulation uses real-world technology and proves its capabilities for this navigation task. The X-ray telescope can be launched into space due to its low weight and size and it will be flown on a mission to Mercury in 2018. Could we be seeing the emergence of a navigation technology that can enable a new era of space exploration?

    And with that look into the future it is time to say “adios” to this column. From now on my EAGER dispatches will be sprinkled through other GPS World imprints and platforms. I’ll be at the global geospatial fun-fest that is Intergeo in Hamburg in October and sniffing around the first Galileo ‘hackathon’ in Berlin in early November, so I hope to see many of you at those and subsequent Euro-GNSS events in the future.

    A bientot as they say in these parts.

    [1] Towards practical autonomous deep-space navigation using X-Ray pulsar timing’ Shemar, S., Fraser, G., Heil, L. et al. Exp Astron (2016). doi:10.1007/s10686-016-9496-z