The Survey Summit agenda format is a bit different this year. First of all, it’s at the Hyatt Hotel next to the San Diego Convention Center. Second, it’s starting two days later, on Saturday, as opposed to starting earlier in the week on Thursday. The first day of the Summit is now a series of lightning talks and presentations followed by a keynote presentation to wrap up the day into the the expo and reception.
1:30 p.m. – 2:15 p.m.Technology PresentationSurveying the New Frontier, Mike Beavers, Frontier Surveying
2:15 p.m. – 2:30 p.m.Break
2:30 p.m. – 3:15 p.m.Keynote PresentationNOAA’s Geospatial Information Officer, Tony Lavoi , NOAA
3:30 p.m. – 6:30 p.m.Survey Summit EXPO and Reception
On Sunday, the technical presentations are in a traditional format (45-minute presentations) on subjects from surveying in the cloud to UAV mapping to handling lidar data. Of course, there’s also the annual discussion of surveying vs. GIS.
There’s no real discussion about GPS/GNSS (albeit a talk about GEOID12) at the Survey Summit, which is surprising given that GPS/GNSS such a prolific tool for surveyors and high-precision GIS users. But, you have to realize that at the end of the day, this is a vendor conference and not an industry conference. I see a real shift going back to state and regional conferences, as opposed to a national surveying conference. It just seems that attendees will get more localized and relevant information in that type of venue, and I also see the trend of state/local conferences bringing in nationally recognized speakers talking about national issues that complement the local speakers and presentations.
Esri International User Conference
Yes, it’s a vendor conference, so you get a lot of Esri Kool-Aid. But, that said, there’s no better place in the U.S. to network with your colleagues about geospatial technologies and issues like this venue. If nothing else, it’s due to the sheer volume of geospatial people that converge on San Diego…~13,000.
Nearly all, if not all of the geospatial technology trends I write about (mobile GIS, BIM, UAVs, GPS/GNSS, RFID, satellite imagery/lidar, etc.) are being discussed at this conference in some form or another. You may have to dig into the agenda a bit to find them, but they are there, and there are plenty of experts attending the conference who are presenting, manning exhibit booths, and otherwise walking around that can answer nearly any question you have. The challenge is finding the people you want to talk to among the 13,000 other people.
I’ll be there all week attending sessions and talking with exhibitors about their work, products, services, and vision. If you want to keep up with me during the week, make sure you follow me on twitter. Twitter is replacing blogging to a certain degree. I’ll be posting photos, links, and interesting comments via Twitter throughout the day, every day at the conferences. You’ll get the latest news in almost real-time.
On Wednesday, I’ll have a professional film crew following me around the User Conference as I talk with different exhibitors and attendees. We’ll produce some pretty neat videos of the conference that will be posted to a special Video Gallery section at 98.27.162.175/gpsworld.com. I’ll be asking exhibitors to talk about their newest GIS, surveying, and mapping products and services, their customers’ requirements and success stories, and any special features they may be unveiling at the show. The videos will be edited to 3- to 5-minute clips for posting to the Geospatial Solutions website. Relevant interviews may also be featured on GPS World’s website.
On Thursday at 10:15 a.m. in Room 31B, I’ll be giving a presentation on the latest developments in GPS and GNSS technology. It’s part of the “Using a Mobile GIS to Manage Assets in the Field” session in the Mobile GIS topic track. I’ll be touching on the newest developments in SBAS, GPS, GLONASS, Galileo, and maybe a little bit about LightSquared. As always, there’s a lot happening in the world of GPS/GNSS and some major changes that you should know about, so stop by and join me.
Esri Acquires ArcPad Developer Maptel
In late-breaking news today, Esri announced it has acquired Austrailian-based ArcPad developer Maptel. This adds an interesting twist to Esri’s mobile GIS development efforts. While it’s been clear that Esri has been pushing ArcGIS for Mobile as the mobile GIS path for the future, the acquisition may be signaling a change in that strategy. ArcPad is the most widely deployed mobile GIS software in the world with well over 500,000 copies deployed. Look for more on this subject from me next week while I’m in San Diego.
Taoglas is launching the AA.16X Dominator series of antennas, which have a wider bandwidth to cover the GLONASS operating frequencies up to 1610 MHz, a good axial ratio, and a double resonance design for optimum reception at the center frequencies.
Taoglas’ GPS antennas are being used in the field by many different M2M solution providers including tracking, telematics, and GPS manufacturers, the company said.
The AA.161 Dominator is a magnetic mount GPS-GLONASS IP67, external antenna incorporating a 35-millimeter ceramic patch. It is a wide-band active patch antenna product with a large integral ground that delivers a gain up to 35 dB. With the Dominator antenna series, Taoglas has a comprehensive range of GPS-GLONASS active embedded antennas (AGGP series) and passive embedded (CGGP) antennas for automotive first-tier TS16949 and after-market applications.
“In the coming months, for the first time the true availability of GPS and GLONASS satellites along with the latest generation of GNSS receivers are going to dramatically change the performance of M2M location devices,” said Ronan Quinlan, Director Taoglas. “With close to double the amount of satellites to draw from compared to a stand-alone GPS constellation, we are now going to see quicker time to first fixes with accuracy improving from meters to sub one meter. The ability to view and lock on four or more satellites in traditionally difficult reception areas such as urban canyons, city centers or locations with restricted views of the horizon, will give M2M manufacturers the ability to triangulate and pinpoint locations with greater accuracy and with quicker time to first fix.
Taoglas’ new Dominator antennas have been rigorously tested and pre-approved by the GNNS receiver companies worldwide and have been shown to display higher and more consistent gain in comparison to competing antennas, the company claimed. Two key components have been engineered from scratch for the Dominator series, a wide-band front-end SAW filter (critical to prevent out of band noise entering on both GPS and GLONASS degrading the signal) and a high-gain 35-mm patch.
CONTACT INFO
Company: Taoglas
Country: United States (USA)
URL: http://www.taoglas.com
Taoglas is launching the AA.16X Dominator series of antennas, which have a wider bandwidth to cover the GLONASS operating frequencies up to 1610 MHz, a good axial ratio, and a double resonance design for optimum reception at the centre frequencies. The company will showcase its line of antennas at CTIA in New Orleans May 8-10.
Taoglas’ GPS antennas are being used in the field by many different M2M solution providers including tracking, telematics, and GPS manufacturers, the company said.
The AA.161 Dominator is a magnetic mount GPS-GLONASS IP67, external antenna incorporating a 35-millimeter ceramic patch. It is a wide-band active patch antenna product with a large integral ground that delivers a gain up to 35 dB. With the Dominator antenna series, Taoglas has a comprehensive range of GPS-GLONASS active embedded antennas (AGGP series) and passive embedded (CGGP) antennas for automotive first-tier TS16949 and after-market applications.
“In the coming months, for the first time the true availability of GPS and GLONASS satellites along with the latest generation of GNSS receivers are going to dramatically change the performance of M2M location devices,” said Ronan Quinlan, Director Taoglas. “With close to double the amount of satellites to draw from compared to a stand-alone GPS constellation, we are now going to see quicker time to first fixes with accuracy improving from meters to sub one meter. The ability to view and lock on four or more satellites in traditionally difficult reception areas such as urban canyons, city centers or locations with restricted views of the horizon, will give M2M manufacturers the ability to triangulate and pinpoint locations with greater accuracy and with quicker time to first fix.”
Taoglas’ new Dominator antennas have been rigorously tested and pre-approved by the GNNS receiver companies worldwide and have been shown to display higher and more consistent gain in comparison to competing antennas, the company claimed. Two key components have been engineered from scratch for the Dominator series, a wide-band front-end SAW filter (critical to prevent out of band noise entering on both GPS and GLONASS degrading the signal) and a high-gain 35-mm patch.
There’s no doubt that geospatial data collected today is more accurate than it was five years ago and will be more accurate five years from now than it is today. A couple of items had me thinking (once again) about the challenge that higher accuracy geospatial is posing and is going to pose in the future.
The first was an interview I did with Dale Lutz this week. Dale is the vice president of software development and co-founder of Safe Software. Dale is a great person to talk to about trends in geospatial data because Safe Software produces geospatial data conversion software tools. Essentially, the company’s software allows users to seamlessly merge geospatial data sets from different sources. For example, a user may have a requirement to merge data sets from AutoCAD, Esri, and Smallworld along with lidar data. Doing so manually can be a terribly laborious task. Not only does the user have to deal with different data formats, but also data of varying accuracy and unknown sources.
“One thing that is an ongoing issue, we see a lot of files that frankly don’t have the right coordinate systems in them or it’s missing, so then that relies on users to know,” said Lutz. “That kind of lack of metadata is going to pose a challenge for people as time goes on because folks aren’t going to remember and the file is going to get passed around. They are not going to know which datum it was collected with and they may not get exactly the correct answer.”
Dale succinctly summarizes the problem. After 20+ years in the geospatial industry, working in many places in the world, and teaching numerous workshops, matching spatial data is the #1 problem people ask me about. It’s fascinating to watch how diligent people are in acquiring the best data collection devices and collecting the most accurate data in the field, only to see it be diluted as it is integrated into a GIS or passed around without the metadata being communicated.
I’m guilty of it as much as anyone. On many mapping projects, I integrate data from several different data sources. Many times the data is a free download from the web with no metadata provided and no technical support. If I’m able to reach someone to ask a detailed question about the data, 90% of the time they will make their best guess as to the datum used and when the data was collected. Was it in the original NAD83 horizontal datum? HARN? NSRS 2007? And even, ugh, NAD27? The difference can be more than a meter or much greater. It doesn’t take much of an error to negate the value of the expensive high-precision GPS receiver you spent thousands of dollars to acquire.
Dale knows all too well. “When we used to deal with a MicroStation file that was accurate to a meter, we didn’t lose too much sleep, but now it’s more of an issue.”
Not only are horizontal datums an issue, vertical accuracy is a challenge of a different kind.
“It’s really doing a good job with the Z (elevation) that is the challenge we are working on. That’s been a big focus for us,” said Lutz.
Another item about geospatial data accuracy I ran into this week was a thread on an Autodesk discussion forum. It was an entertaining thread about parcel maps and how they don’t reconcile nicely.
The original poster summarizes the problem:
“I am trying to draw a parcel map in AutoCAD, using the distance and bearing info that was added by to the original hand-made drawing by the surveyor. The parcels don’t quite close perfectly… Does anyone know what the acceptable tolerances are for parcels of say 1 acre and under, 1-5 acres, and 5-20 acre sites? Will it ever close EXACTLY, or am I a dreamer?? WOuld you send the surveyor back out to take new measurements if, lets say, he was off by .3″? Or a foot? Or 4 feet on a huge parcel? I am new @ this and just getting started. Thanks!”
An obviously well-informed poster responded:
“That is one major open-ended question…
There are all kinds of things that come into play. Some of it is the age of the original plat. There are many places around our country where we have plats created in the 1700’s, using the proverbial “one-eyed goat and a rope”. Those surveys could have major errors, when compared to what we can achieve with today’s technology. But there’s a whole string of law that decides how all of that gets resolved, and it favors the “original survey” whenever possible. But above that, it favors any monuments that are found and recovered. Those typically hold precedence, even if they disagree with the legal record.
There are also standards that you may need to live to now, in our current age, especially if you’re doing something like an ALTA (Land Title) Survey. You have to make sure to perform within the standards set by the law. With today’s technology, this is often relatively easy, but you still may run into issues when dealing with older neighborhoods, laid out in past times when measurements were not as exact, and especially when original monumentation can’t be found… It can get worse; sometimes you find inconsistent monumentation, and have to try to sort through different surveys, figuring out which monuments were set when… It can become quite a puzzle.
Learning all of this stuff is what becoming a professional land surveyor is about. And it takes years to do that. So there’s no real way to explain it all in a forum post.”
Finally, in one sentence the same poster summarizes the colliding worlds of digital cartography, one of the newest digital technologies, and land surveying, one of the oldest professions.
“A jig-saw puzzle made by blind men with dull saws. As I sometimes describe it.”
Two weeks ago I gave a presentation, at the Transportation Research Board (TRB) annual meeting. This is one of those mega-meetings attended by almost anyone involved in the transportation related professions. TRB is part of the National Research Council jointly administered by the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. TRB’s active members include more than 7,000 engineers, scientists, and other transportation researchers. The program is supported by state transportation departments and federal agencies including the U.S. Department of Transportation.
The TRB annual meeting is huge — 11,000 attendees spread out among eight D.C. area hotels in four main venues. TRB is involved in every possible aspect of transportation: public transportation including highways, mass transit, aviation and marine, and freight movement by rail, water and pipelines. With more than 4,000 presentations, it reminded me a lot of the ESRI Users Conference — absolutely impossible to see and hear it all.
The presentations ran the gamut from political and financial, engineering and construction to advanced research into safety, human factors, energy and the environment. As you would expect there were many presentations that were Greek to me, as I’m sure some of the geospatial ones were Greek to other attendees. There were a lot of engineering/construction-related sessions. A significant number of advanced research presentations dealt with statistical analysis of factors related to highway safety, including a heavy emphasis on the mind-eye interaction. Even the poster sessions were tough to comprehend, with a lot of statistical analysis covering human factors related to safe highways. Although I had calculus and calculus-based statistical courses, it hurts my head to see a lot of integral signs in a poster. The learning curve to understand the work is just too tough in a “drive-by” viewing.
Several sessions dealt with FAA GIS and the NextGen air control system in particular. See the column on Airport GIS for more details and to understand where we are headed in aviation. The GIS-related presentations were concentrated in a track under the broader concept of Virtual Design and Construction (VDC). These sessions were organized by Lance Parve, MSCE of the Wisconsin DOT, Charles Hixon of Bergmann Associates and Kevin Gilson of Parsons Brinckerhoff. They did an exceptional job of tying together visualization, GIS, CAD and BIM with a focus on interoperability in final construction.
My attendance was prompted by a presentation I did in August at the once-every-5-year TRB Visualization Symposium. The conference committee invited three presenters out of 120 to speak at the TRB Annual Meeting, so I was pleased to be one of the three. I spoke about the benefits of oblique imagery and related 3D models for planning, public safety and public involvement meetings.
I wrapped up my presentation by highlighting the superb example of a 3D web application for public involvement visualization built by Fairfax County under the leadership of Tom Conry.
Combining GIS and GPS technology, David Brown of Delcan explained how his firm kept track of quality control inspection results using Trimble GeoXT GIS GPS Data Collectors. His team of inspectors recorded each inspection point and inspection results in a GIS. The collection and creation of the GIS database was accomplished quickly and efficiently using the GeoXTs to capture the location and inspection values in one step. They also used cameras to record problems and bar codes/readers to speed data entry. At left is a GIS plot of all the data points. The GIS analysis tools helped identify clusters of poor samples that signaled the start of quality issuesso they could be corrected early in the construction process.
There were sessions on LiDAR point cloud captures and converters to 3D models. A very impressive example was TopoDOT by Certainty 3D is a MicroStation application for extracting topography and digital models from point clouds. The system tool suite extracts ground topography quickly and accurately from airborne, mobile or terrestrial point clouds and calibrated images. It then extracts breaklines, elevations, cross-sections, and other DTM componentsaccording to project requirements.
Not surprising is that the common thread was a path to BIM models. Civil engineers have adopted BIM models aggressively and all this technology has led to VDC (Virtual Design and Construction) a technology wave that is revolutionizing the construction industry. In March 2011, I wrote about how even Granite Counter Tops were being measured, digitized and the digital design models fed directly into the digital controlled stone cutting machines to fabricate the tops quickly and accurately. The same kind of process is revolutionizing civil engineering.
Back in the Paleozoic era, when I was in college, I worked part time in a machine shop. Traditional machining was done by moving rotating cutting tool across metal blanks to create objects described in mechanical drawings.The machinist did this by manually turning operating wheels that adjusted the cutting tool to fabricate the part according to the design blueprint. Early automation at that time, called Numerical Control, used digitally controlled motors to move the same cutting tools according to predefined paths to make the same parts. There was considerable time spent manually programming the machines to do the jobs. Current technology, just like the granite cutting system, goes directly from the digital design to fabrication of the finished product.
The same process is being done on a mega scale with bulldozers and other heavy earth-moving machines. You may remember that a number of years ago farmers started using aerial CIR imagery to map soil and water conditions of their land. They then used GPS to do precision farming by metering the optimal distribution of fertilizer based on mapped water content and the location of their tractor relative to the GIS data. The same kind of GPS machine control has been perfected by companies like Trimble and John Deere.
On the right is a bulldozer that is accomplishing its work no differently than a machine shop milling machine or precision farming tractor. There are GPS receivers mounted on each end of the dozer’s blade. The operator in the cab can be guided by the CAD image or turn over steering and blade depth control to the automated system. There is no longer a need to place wood marker stakes and constantly survey the progress of the excavation. The bull dozer operator is clearing the land at double speed guided by GPS and a GIS/CAD/BIM 3D model.
It’s strange seeing this kind of automation and precision in heavy earth moving equipment, but this type of technology is making inroads into all phases of construction. So next time you pass a major construction site, see how many GPS receivers you can spot and appreciate the GIS link.
By Jared B. Bancroft, Valérie Renaudin, Aiden Morrison, and Gérard Lachapelle
INNOVATION INSIGHTS by Richard Langley
GPS IS VIRTUALLY UBIQUITOUS with more than 400 million units estimated to be in use in the United States alone. Some of these units are standalone devices such as those used in surveying and timing applications and those used for vehicle navigation or tracking with permanent or temporary mountings. However, the majority of the units are integrated into cellular telephones, tablet computers, personal digital assistants, watches, cameras, and other devices, which are designed to be operated in close contact with the human body. We even now have GPS shoes!
It is well known that the performance of the antenna of a radio receiver can be affected when it is used in close proximity to the human body. We only have to touch the whip antenna of a portable AM/FM or scanner radio to convince ourselves of the effect. So, when we use a handheld GPS receiver or wear a GPS watch, or put a GPS-equipped cellular telephone up to our ear, are there any effects on the operation of the receiver?
It turns out that there are four major effects that can change the performance of a GPS (or other GNSS) receiver antenna when placed near or on the human body. The impedance of the antenna may be changed causing a drop in power transfer to the receiver front end. The center frequency and bandwidth of the antenna may be changed again resulting in a loss of received power. The gain pattern of the antenna may be changed. However, the change may be favorable, improving reception for a given satellite azimuth and elevation angle. And lastly, there will be close-range multipath between the antenna and the body skin.
All of these factors need to be taken into consideration when a manufacturer is designing a GPS unit to be operated in close proximity to a human body. Trade-offs might be possible and certain designs may make the antenna less likely to interact with its surroundings.
But how does one go about assessing the antenna’s performance in a repeatable and quantifiable way?
In this month’s column, a team of researchers from The University of Calgary report on tests conducted on two different types of GPS antennas operated in the vicinity of a human phantom — an artificial body with similar electromagnetic properties as that of a real human.
“Innovation” features discussions about advances in GPS technology, its applications, and the fundamentals of GPS positioning. The column is coordinated by Richard Langley, Department of Geodesy and Geomatics Engineering, University of New Brunswick. To contact him with topic ideas, email him at lang @ unb.ca.
GNSS-based navigation is the foundation of many pedestrian navigation systems. The use and benefit of GNSS receivers to locate people has increased dramatically over the past few years. Pedestrian navigation applications include mobile phone users, first responders, health and activity monitoring, consensual tracking (such as offender management), recreational use, and tracking of military personnel. GNSS navigation systems are commonly available in watches and personal entertainment devices. Some applications contain GNSS receivers and antennas in shoes, glasses, and jackets. Since each application using a GNSS receiver to locate people requires an antenna, the optimal type, size, and location on the body is becoming increasingly important.
This article addresses adverse antenna effects when the antenna is placed near or on the human body, specifically in the reactive near field at the GPS L1 frequency. Using real data collected on a human phantom over prolonged periods, the changes within the antenna are observed as a function of distance from the body. Thus, a performance profile can be generated to quantify the power loss incurred by loading the antenna. The study applies equally well to all GNSS operating at or near the GPS L1 frequency.
The researchers have theoretically addressed performance of GPS antennas in close proximity to a human body. Using simulations to provide analysis of antenna detuning effects, one research group showed a 24.4-MHz shift in the resonance frequency of the antenna when placed 10–40 millimeters from a simulated human chest. The resonance shift was common at all distances, although the return loss decreased as the antenna was moved further away from the chest.
A few studies have developed antennas to be located in protective (or otherwise) garments for specific applications. Our team previously analyzed the impact of antenna location on the human body by comparing the solution of eight identical and simultaneous navigation solutions.
Antenna-Body Interaction
Antenna detuning refers to the consequence of the electrical interaction between an antenna and an adjacent object, the body of a user in this context, which causes the center frequency of the antenna to deviate from the desired center frequency. More generally, there are several effects that serve to degrade antenna performance that arise when an antenna operates near the body of a user.
The first of these effects is a change in the impedance of the antenna, as shown in FIGURE 1. (See online sidebar for antenna and electromagnetic radiation term definitions.) The change results in the impedance of the antenna no longer properly matching that of the network that it is expected to drive, therefore causing incomplete power transfer between the antenna element and the subsequent radio-frequency (RF) stages.
Selected Antenna and Electromagnetic Radiation Terms
Axial ratio. A measure of the polarization ellipticity of an antenna designed to receive circularly polarized signals. An axial ratio of unity, or 0 dB, implies a perfectly circularly polarized antenna.
Bandwidth. The range of frequencies over which an antenna is designed to operate efficiently. The bandwidth limits are typically determined by a particular reduction in gain compared to that at the antenna’s center frequency; for example, 3 dB or 10 dB.
Conductivity. A measure of a material’s ability to conduct an electric current. The reciprocal of resistivity. Units are mhos per meter.
Dielectric. A material in which there are no free charges that can move through it under the influence of an electric field. An insulator. However, minute displacements of positive and negative charges in opposite directions are possible. A dielectric in which this charge displacement has taken place is said to be polarized.
Far field. The area sufficiently far from an antenna where the gain pattern is essentially independent of distance. In the far field, the power of an electromagnetic wave traveling in free space drops off as the square of the distance from the transmitting antenna.
Fresnel reflection coefficient. A measure of the degree of reflection of an electromagnetic wave at the interface between two media. Dependent on the properties of the media, the polarization of the wave, and the angle of incidence.
Gain. For a transmitting antenna, the ratio of the radiation intensity in a given direction to the radiation that would be obtained if the power accepted by the antenna was radiated isotropically. For a receiving antenna, it is the ratio of the power delivered by the antenna in response to a signal arriving from a given direction compared to that delivered by a hypothetical isotropic reference antenna.
Gain (amplitude) pattern. The spatial variation of an antenna’s gain.
Human phantoms. Models of parts of the human body used in engineering, science, and medical studies designed to mimic a particular physical, chemical, or electrical behavior.
Impedance. The complex ratio of the voltage to the current in an alternating current circuit. Sometimes called complex resistance in which case the absolute value of the complex resistance is called the impedance. Units are ohms.
Lossy material. A material in which a significant amount of the energy of a propagating electromagnetic wave is absorbed (dissipated) per unit distance traveled by the wave.
Near field. The region around an antenna within a few wavelengths where there are strong inductive and capacitive effects from the currents and charges in an antenna that cause electromagnetic components not to behave like far-field radiation. Within the radiating part of the near field, the gain pattern is dependent on the distance from the antenna.
Polarization. The sense of vibration of electromagnetic radiation. There are two main types of polarization: linear, in which the radiating wave’s electric field vector is confined to a particular direction (typically vertical or horizontal); and circular, where the electric field vector rotates as the wave propagates through space. Depending on the sense of rotation, a signal’s waves may be left-hand or, as with GPS signals, right-hand circularly polarized. For maximum response, the polarization of a receiving antenna should match the polarization of the signals.
(Absolute) Permittivity. A measure of how an electric field affects, and is affected by, a dielectric material. In a sense, it describes a material’s ability to transmit (or “permit”) an electric field. Since the response of most materials to external fields generally depends on the frequency of the field, permittivity is expressed as a complex quantity with real and imaginary components as a function of frequency. Units are farads per meter.
Relative permittivity. The ratio of the permittivity of a material to that of free space or a vacuum. Also called the dielectric constant. Unitless.
Return loss. A measure of the effectiveness of power delivery from a transmission line to a load such as an antenna or vice versa. If the power incident on an antenna is Pin and the power reflected back to the source is Pref, the degree of mismatch between the incident and reflected power in the traveling waves is given by the ratio Pin/Pref. Units are dB. Functionally related to the Fresnel reflection coefficients and VSWR.
Voltage standing wave ratio (VSWR). A measure of the size of the reflected waves in a transmission line due to impedance mismatches between the line and a connected antenna. The ratio of the maximum voltage along the line to the minimum voltage along the line. Ideally, an antenna should have a VSWR value of unity.
FIGURE 1. Change in the reactive portion of the impedance of a patch antenna versus separation distance between the antenna element and imitation human skin (Courtesy, Buckley et al., 2010; see Further Reading).
The figure provides an example of the impedance for a patch antenna plotted against the separation distance of a simulated human wrist. When mounted directly on the user’s skin surface, this specific antenna gains significant reactive impedance that results in a large voltage standing wave ratio (VSWR) with the network.
A second effect of antenna proximity to human skin is the alteration of the center frequency, as well as the alteration of the antenna bandwidth. Depending on the bandwidth of the signal of interest, the bandwidth of the antenna element, and the degree of center-frequency shifting and bandwidth loss experienced, these factors can contribute to significant loss of received power.
Thirdly, it is important to note that in some configurations, a “lossy” medium adjacent to an antenna may improve the apparent performance of the antenna due to changes in its gain pattern that result in better receive or transmit performance for a given azimuth and elevation angle.
For any application in which the antenna may be either in free space or directly adjacent to a lossy medium such as a human body, the use of balanced antennas is recommended. The image current of a balanced antenna is contained within complementary structures of the antenna itself, not within the casing or adjacent material of the antenna, therefore making the antenna much less likely to interact with surrounding media.
Fourth, the close proximity of a reflective material increases close-range multipath. If the distance between the reflector (that is, skin) and the antenna is close to half a wavelength, giving a 180º phase shift of the carrier, deconstructive interference can occur. There are several factors that contribute to this including the back lobe of the antenna gain pattern, reflection coefficient of the skin beneath the antenna, and the incident angle of the incoming ray. Approximation via simple ray tracing becomes dauntingly complex due to the variation of the antenna properties listed above, resulting from detuning. Therefore, observation of the effect becomes easier than modeling an incoming ray and its multipath counterparts.
Phantom Body Simulation
To conduct an assessment of the impact of the human body on the radiation patterns of diverse antennas in the context of tracking GNSS signals, a human body phantom has been designed for collecting the experimental data. Variations of the locations and orientations of the antenna rigidly mounted on a human shoulder, head, or any other locations would render the repeatability and comparison of the collected data hardly feasible. Furthermore, the distance that separates the antenna from the human body surface could only be precisely controlled using an artificial modeling of the human body. Therefore, a human body phantom is required for productive analysis.
Because the human body is mainly composed of water, the presence of human tissue in the vicinity of the antenna introduces an absorption and reflective effect that alters the performance of the antenna. Different mathematical models have been developed for representing the different component combinations of a human body. Based on the study of numerous women and men of different ages and sizes, a classic model predicting the fat-free mass of a person has been developed and assumes that 73 percent of a human body consists of water. Looking at the elemental composition in the human body, it can be found that a concentration of 7 grams of salt per liter of water provides an acceptable modeling of the human tissues. Complex shapes of the human body are used for modeling more precisely the layered structure of the human tissues using either a more realistic human phantom or a more detailed model comprising the extensive data on the dielectric properties of each layer constituting the human tissues of interest. For context of this study, the phantom was kept simple and was made of a large plastic container filled with a 7 percent concentration of a saline solution.
The radiative transfer of the human body phantom on the reception of GNSS signals can be evaluated through the understanding of the dielectric permittivity of the solution. Different models, including the Wagner, Debye, Cole & Cole, or Fricke, are commonly used for studying the dielectric behavior of biological tissues. The Debye model gives the permittivity of an aqueous saline solution of salinity, S, at a fixed temperature, t, as
(1)
where
is the angular frequency (Hz),
εi equals 8.8419 ×10-12 (farads per meter),
τ is the relaxation time (seconds),
σ is the ionic conductivity of the dissolved salts (mhos per meter), and
ε0 and ε∞ are the static and high frequency dielectric constants.
Equation (1) gives the dielectric proprieties of the human phantom solution for a specific temperature, saline concentration, and temperature. The experiments we conducted and report on in this article lasted several days and were conducted outside, which unfortunately resulted in temperature fluctuations. Consequently, the 7 percent saline solution over the temperature range of 11º to 31º C for L1 (1575.42 MHz) results in a 9 percent variation of permittivity. As shown in FIGURE 2, the dielectric constant over the experimental temperature range is in the interval [74.6, 81.9]. Because the variation is small, the permittivity value can be closely approximated to a mean value of 78.
FIGURE 2. Real part of the permittivity of the human body phantom as a function of temperature for the GPS L1 frequency.
Reflection Coefficient of the Phantom Body
The Fresnel reflection coefficients for a smooth flat surface depend on frequency, the incident angle, polarization, and ground characteristics. Since the container is full of salted water it can also be considered a reflective surface.
The relative permittivity of the saline solution given in Equation (1) can be reformatted as
(2)
The reflection coefficients with vertical and horizontal polarizations, respectively, of the electromagnetic wave on the surface of the saline water are given by the following Fresnel equations:
(3)
(4)
where Rv and Rhare the vertical and horizontal polarized reflection coefficients, respectively, and θ is the incident angle.
Assuming that the water surface is flat and infinite, Equations (3) and (4) are plotted against the incident angle in FIGURE 3. The reflection coefficients were estimated using a mean temperature of 21°C, a salt concentration of 7 percent and at the L1 frequency.
FIGURE 3. Fresnel coefficient for L1 considering a flat surface of salted water.
While the saline solution of the human phantom has an angle of incidence and direction of polarization dependent on reflectivity, the fact that the GPS carrier is circularly polarized must be considered. Due to the circular polarization of the carrier and that of most antenna elements intended for GPS use, the received signal strength of the reflected wave will always appear to be equal to or higher than that of the reflected portion of the horizontal polarization.
Test Setup
To evaluate the change in gain pattern as function of distance from the phantom, we collected 24-hour data segments. These segments allowed the receiver to observe all satellites. A high-performance GPS L1 receiver module evaluation kit was used with two antennas. The first was a patch antenna while the second was a quadrifilar helix antenna. FIGURE 4 shows both antennas without their coverings. Each antenna has a built-in low noise amplifier (LNA). The antenna specifications are listed in TABLE 1.
FIGURE 4. Patch (above) and quadrifilar (below) antennas used in the tests.TABLE 1. Antenna specifications.
A water container holding the saline solution was placed on the roof of a building as shown in FIGURE 5. The container had a slight inclination to move a small air pocket to the corner of the container away from the antenna. After a successful 24-hour data collection period, the antenna was supported by a small plastic box and oriented in the same direction. Six vertical distances were selected, namely 0, 11, 22, 30, 41, and 52 millimeters.
FIGURE 5. Data collection with patch antenna fixed to phantom body.
The gain pattern as measured by the C/N0 values of the path antenna is shown in FIGURE 6. In general, the largest effect is seen near the zenith where the power decreased by 10–15 dB when the antenna was 22 millimeters from the phantom body. It is also observed that the effect is maximized at 22 millimeters, and then reverts back to near normal operation at 52 millimeters. Additionally, at lower elevation angles (< 30º), the gain behaves more linearly, where the largest distance has the least gain, while the smallest distance has the most gain. The effect of the phantom body appears to flatten the gain pattern.
The pattern shown in Figure 6 shows the effect of the proximity to the phantom body over all elevation angles. However, a prominent pattern emerges for measurements made at elevation angles of 45º and 85º. In the case of a 22-millimeter antenna distance from the body, a significant power decrease occurs. For satellites with an 85º elevation angle, nearly 8 dB is lost compared to 5 dB loss at a 45º elevation angle.
FIGURE 6. Gain pattern of the patch antenna as measured by the measured C/N0 at all elevation angles as a function of antenna distance from body. Elevation angles [0º, 90º] have azimuths [180º, 360º], while elevation angles [90º, 180º] have azimuths [0º, 180º].FIGURE 7 provides the trend as a function of distance from the body. The trend of the power loss at 22 millimeters is common on all measurements, albeit more significant for higher-elevation-angle satellites. For satellite measurements made at an 85º elevation angle, the power varies by 12 dB. When all measurements are considered, which includes more frequent lower-elevation-angle satellite measurements and the fact that the gain pattern deviates significantly at higher elevation angles (as shown in Figure 6), the fluctuation is less prominent.
FIGURE 7. Mean C/N0 measurements of the patch antenna from all measurements and those only at 45º and 85º elevation angles as a function of antenna distance from the body.
To assess the cause of the impact, we removed the phantom and replaced it with a flat aluminum reflector placed beneath the antenna. The antenna was then placed at the same distances above the reflector as previously. Since the gain pattern had been established and this test was to observe the effect of the reflector, only 60 seconds of data was collected at each distance.
FIGURE 8 provides the change in C/N0 for two tests, which has a comparable trend to that of Figure 7. From the corroboration of the two tests, it appears that the salt water provides similar multipath effects to that of the aluminum sheet. The power loss is then attributed to destructive interference.
FIGURE 8. Mean C/N0 measurements (over 60 seconds) of satellite PRN 8 with 85º elevation angle when placed above an aluminum reflector.
Similar data collections were conducted with the quadrifilar helix in order to assess its ability to perform close to the human phantom. The quadrifilar antenna has the LNA circuitry vertically below the antenna and therefore was placed horizontally on the water container. FIGURE 9 shows its gain pattern. The overall C/N0 is lower but is subject to less variation compared to that of the patch antenna. In general, we noticed lower C/N0 values with the quadrifilar antenna, regardless of the environment and despite the LNA having 5 dB more amplification. Some moderate variations of up to 10 dB appear on the east side of the antenna (zenith angle [0º, 90º]), but overall the pattern appears to be more regular.
FIGURE 9. Gain pattern of the quadrifilar antenna as measured by the C/N0 of all measurements as a function of antenna distance from body. Elevation angles [0º, 90º] have azimuths [180º, 360º], while elevation angles [90º, 180º] have azimuths [0º, 180º].The overall power variation was assessed in a similar method. FIGURE 10 shows cubic-like functions with 3-dB variations. There is also no consistent downward power loss trend at 22 millimeters as observed with the patch antenna. As expected, due to the balanced nature of the quadrifilar antenna, the degree of apparent power loss caused by adjacent material is substantially lower compared to the patch antenna. While the peak level of power received is not as high as that experienced with the patch antenna, the consistency of the received power level is better.
FIGURE 10. Mean C/N0 measurements of the quadrifilar antenna from all measurements and those only at 45º and 85º elevation angles as a function of antenna distance from the body.
Conclusions
We have investigated the impact of the proximity of the human body on received signal power associated with operation of L1 GPS antennas through experimental tests. GPS signals have been collected using two different antenna types (a patch antenna and a quadrifilar helix antenna), placed on a human body phantom with different separation distances. A strong relationship between these distances and the averaged received signal power has been observed for both antennas with overall lower C/N0 values for the quadrifilar antenna. The largest attenuation is not observed when the antenna is directly adjacent to the user body but when it is about 22 millimeters above it. We found that the attenuation mainly results from destructive interference due to multipath. These results suggest that body-mounted GPS antennas should be directly in contact with the user’s body for achieving better tracking performance. Our future research will include theoretically assessing the experimental results for better understanding of the underlying effects.
Acknowledgments
This article is based on the paper “GNSS Antenna-Human Body Interaction” presented at ION GNSS 2011, the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation, Portland, Oregon, September 19–23, 2011. The authors would like to thank Prof. Ron Johnston, Dept. of Electrical and Computer Engineering, The University of Calgary, for his insight and consultation in preparing that paper. We thank John Buckley, Tyndall National Institute, Ireland, and his co-authors for permission to use Figure 1, a version of which appears in “The Detuning Effects of a Wrist-Worn Antenna and Design of a Custom Antenna Measurement System” (see Further Reading).
Manufacturers
The tests discussed in this article used a u-blox AG EVK-6T evaluation kit using a LEA-6T L1 GPS module, an Allis Communication Co. Ltd. M827B active L1 patch antenna, and a Sarantel Ltd. SL1206 active L1 quadrifilar helix antenna.
Jared B. Bancroft is a senior research engineer in the Position, Location And Navigation (PLAN) Group in the Department of Geomatics Engineering at The University of Calgary in Calgary, Alberta, Canada. He received his Ph.D. in geomatics engineering in 2010 and has worked in the area of navigation since 2004. Dr. Bancroft’s research interests include pedestrian and vehicular navigation through data fusion of sensors and satellite navigation data.
Valérie Renaudin is a senior research associate in the PLAN Group. She received an M.S. in geomatics engineering from the Ecole Supérieure des Géomètres et Topographes, France, in 1999 and a doctorate in geomatics engineering from the Ecole Polytechnique Fédérale de Lausanne, in 2009. She was previously the technical director at Swissat AG. Her research interests include low-cost sensors, hybridization techniques, magnetometers, and indoor navigation.
AidenMorrison is a senior research associate in the PLAN Group. He received his B.Eng. in electrical engineering from Ryerson University, Canada, in 2006 and a Ph.D. in geomatics engineering from The University of Calgary in 2010. His research interests include development of integrated navigation systems.
Gérard Lachapelle holds a Canada Research Chair in Wireless Location in the Department of Geomatics Engineering at The University of Calgary, where he has been a professor since 1988 and heads the PLAN Group. He has been involved in a multitude of GNSS R&D projects since 1980, ranging from RTK positioning to indoor location and GNSS signal processing enhancements.
Further Reading
• Previous Work by Authors
“GPS Observability and Availability for Various Antenna Locations on the Human Body” by J.B. Bancroft, G. Lachapelle, T. Williams, and J. Garrett in Proceedings of ION GNSS 2010, the 23rd International Technical Meeting of the Satellite Division of The Institute of Navigation, Portland, Oregon, September 21–24, 2010, pp. 2941–2951.
• Interaction between Receiving Antennas and Human Body Parts
“The Detuning Effects of a Wrist-Worn Antenna and Design of a Custom Antenna Measurement System” by J. Buckley, K.G. McCarthy, B. O’Flynn, and C. O’Mathuna in Proceedings of the 40th European Microwave Conference, Paris, France, 28–30 September 2010, pp. 1738-1741.
“One-Layer GPS Antennas Perform Well Near a Human Body” by T. Kellomaki, J. Heikkinen, and M. Kivikoski in Proceedings of EuCAP 2007, the Second European Conference on Antennas and Propagation, Edinburgh, Scotland, November 11–16, 2007, 6 pp.
“Effects of Human Body Interference on the Performance of a GPS Antenna” by M. Ur Rehman, Y. Gao, X. Chen, C.G. Parini, and Z. Ying in Proceedings of EuCAP 2007, the Second European Conference on Antennas and Propagation, Edinburgh, Scotland, November 11–16, 2007, 4 pp.
• Wearable Antennas
“Design of a Protective Garment GPS Antenna” by L. Vallozzi, W. Vadendriessche, H. Rogier, C. Hertleer, and M.L. Scarpello in Microwave and Optical Technology Letters, Vol. 51, No. 6, June 2009, pp. 1504–1508, doi: 10.1002/mop.24372.
“Wearable Antennas in the Vicinity of Human Body” by P. Salonen, Y. Rahmat-Samii, and M. Kivikoski in Proceedings of the IEEE Antennas and Propagation Society International Symposium, Monterey, California, June 20–26, 2004, pp. 467–470, doi: 10.1109/APS.2004.1329675.
“A Small Planar Inverted-F Antenna for Wearable Applications” by P. Salonen, L. Sydänheimo, M. Keskilammi, and M. Kivikoski in Digest of Papers, the Third International Symposium on Wearable Computers, San Francisco, California, October 18–19, 1999, pp. 95–100, doi: 10.1109/ISWC.1999.806679.
• Dielectric Properties of Human Tissue and Sea Water
“New Permittivity Measurements of Seawater” by W. Ellison, A. Balana, G. Delbos, K. Lamkaouchi, L. Ey, C. Guillou, and C. Prigent in Radio Science, Vol. 33, No. 3, 1998, pp. 639–648, doi: 10.1029/97RS02223.
“Studies on Body Composition. III. The Body Water and Chemically Combined Nitrogen Content in Relation to Fat Content” by N. Pacen and E.N. Rathurn in Journal of Biological Chemistry, Vol. 158, 1945, pp. 685–691.
• Human Phantoms
“Solid Phantoms for Evaluation of Interactions Between the Human Body and Antennas” by K. Ito and H. Kawai in Proceedings of IWAT 2005, the 2005 IEEE International Workshop on Antenna Technology: Small Antennas and Novel Metamaterials, Singapore, March 7–9, 2005, pp. 41–44, doi: 10.1109/IWAT.2005.1460993.
“A High-Precision Real Human Phantom for EM Evaluation of Handheld Terminals in a Talk Situation” by K. Ogawa, T. Matsuyoshi, H. Iwai, and N. Hatakenaka in 2001 Digest, IEEE Antennas and Propagation Society International Symposium, Boston, Massachusetts, July 8–13, 2001, Vol. 2, pp. 68–71, doi: 10.1109/APS.2001.959623.
There’s been a tremendous push in the past three decades to map what is outdoors. While there is still a long way to go, the path to a complete, accuracy outdoor GIS seems clear. On the other hand, mapping the unseen and indoors is in its infancy, and the path to a complete and accurate GIS of unseen infrastructure (eg. underground) and indoors (eg. building infrastructure) is not clear.
Cost-effective and efficient methods of data collection are the primary reasons for the proliferation of outdoor GIS. Remote sensing (satellite/aerial imagery, lidar, etc.), GPS, and other sensors have become common technologies for populating an outdoor GIS. If one studies the data sources in a typical GIS, they can be sourced to one of the technologies mentioned above.
The challenge of populating a GIS with spatial details of hidden infrastructure and indoor features is purely a function of efficient and cost-effective sensors. Satellite/aerial imagery doesn’t help and GPS doesn’t help in either case. Therefore, new sensor technologies must be adopted that make data collection efficient and affordable. The good news is that there are many
INTERGEO, held in Germany every year, is the best all-around geospatial conference that allows vendors to showcase their technologies. With ~17,500 attendees, it’s certainly the largest geospatial conference in the world. From my experience, it’s also the best.
Simply, INTERGEO attracts vendors who offer a collection of technologies from GPS/GNSS to remote sensing, 3D scanners, and mapping software that would satisfy the curiosity and needs of any geospatial professional. As I wrote last year, don’t expect to be tied up in sessions, this is a trade show where people come to visit the vendor booths, and the foot traffic is non-stop.The display booths are fantastic. Check out Topcon’s booth below. The seating looks like the airliner I flew in to Germany on.
Topcon introducing Magnet, their Cloud-Based Precise Positioning Solution
Lidar data processing and management software, such as Terrasolid’s solution, was common at INTERGEO. As the cost of high-precision data becomes much cheaper to collect, the bottle-neck becomes data processing and management.
Lidar data management
3D mobile mapping was a hot topic. This 3D Laser Mapping vehicle was used to help assess damage in Japan after the March 11, 2011 earthquake.
3D scanning autos were abound on the trade show floor
The world’s leading GNSS receiver manufacturers attend in full force. You’ll see every major vendor.
Javad GNSS displaying their receivers as well as their new iPad app
As expected and reported over the past few years, the market for machine control products is developing and expanding. There were a number of interesting displays, including this one from Moba AG.
Demonstration of Moba’s excavator machine control system
UAV’s (Unmanned Aerial Vehicle) also continue to be a hot topic. The benefits of UAV for remote sensing geospatial activities are clear. What’s not clear is the commercial adoption of UAVs for mapping. Europe and other countries have been much more progressive than the U.S., which still severely limits the use of UAVs for non-government and non-university activities.
Of course, BIM (Building Information Modeling) is another significant trend and there were no lack of vendors at INTERGEO on that topic. The GIS world has just started to get a handle on mapping outdoors while indoor mapping is vastly untouched. OrthoGraph displays their indoor mapping app for the iPad.
OrthoGraph Architect for iPad
I heard some good things about OpenStreetMap. I’ve written about OSM before. Take a look at their website when you have a chance. Also exhibiting was OpenSeaMap.
Open Street Map stand
At the Nuremberg Messe, there was plenty of space to accommodate the ~17,500 attendees as well as an outdoor demonstration area.
INTERGEO 2011 outdoor demonstration area
On the second day of the INTERGEO conference, the Forum for Satellite Navigation (SatNav-Forum) held its one-day meeting. This was the first time it was co-located with INTERGEO. You can view the agenda here, though it’s in German so you’ll need to use an online translator. Note that yours truly gave a short presentation in the afternoon. Some Galileo literature I read tried to make the point that Galileo is superior to GPS and GLONASS. I tried to make the point that GPS and Galileo (Europe’s GPS) are complimentary systems, not competitive systems. By using both GPS and Galileo, high-precision horizontal and vertical data will be very easy and inexpensive to collect in the future. I hope I made my point.
SatNav-Forum display at INTERGEO
Back to the INTERGEO conference. If your company manufacturers something related to geospatial hardware or software, you’re making a big mistake if you are not attending INTERGEO. This is, by far, the single best conference in the world to attend in order to understand the latest trends and developments in GIS, surveying, engineering, and all other geospatial-related disciplines.
Four weeks ago I attended a USSOCOM and Navy Post Graduate School event known simply as Camp Roberts TNT. Located in a remote part of the California Central Valley near the town of Paso Robles, the best way to describe Camp Roberts is that it’s like a Boy Scout Jamboree for engineers, scientists, and military operators. However, Camp Roberts focuses on the serious business of Special Operations that was made even more somber by the loss of 30 Navy SEALS the day before the start of the event.
Sunday, as I was packing to go to Camp Roberts, I couldn’t help but reflect on the loss of the Special Operations team that day. I knew that throughout the country there were 30 Navy and Marine Corps officers putting on their dress uniforms to personally deliver the most horrific news a family can get. Each officer held a message that would turn into a dagger which would penetrate and twist in the heart of a mother, wife, or children. At Camp Roberts many attendees had personal connections to the lost troops but everyone hunkered down to the business at hand.
The USSOCOM Camp Roberts TNT (Tactical Network Testbed) was well attended with more than 850 registered attendees. Camp Roberts is about 15 miles from the charming wine country town of Paso Robles. The camp is mostly dirt roads and gravel, 42 degrees in the morning up to 98 by noon. There are two primary buildings (double wides): a large briefing room that was designed for about 80 but packed with 200, and the TOC (Tactical Operations Center) with numerous flat screens showing different displays depending on who was demonstrating.
Unlike trade shows, TNT is mostly live equipment demos, outside, in the dirt with very informal discussions. But unlike contract delivery testing, perfection was not expected since some of the equipment was still in the development stage. Uniform of the day was khakis, jeans, T-shirts, polo shirts, caps and water bottles. Lunch was a vendor tent with hot dogs, chips and drinks. TNT has become so popular, that other COCOMs are looking to start their own.
Every morning there was a group meeting led by Dr. Buettner (NPS, retired Navy) who heads up the TNT effort. The staff reviews the plan of the day, demos, weather, safety (heat, snakes, foxes, elk, moving equipment, etc.) and logistics. Each participant quickly explains their demo, time, and location. I highlighted my 30-minute lunch time session on oblique imagery. Dr. Buettner, who has a dry sense of humor, interjected that I may or may not be there in November with a live aircraft demo if the audience gives me a thumbs down. I had good attendance at my presentation and closed by asking for a show of hands if we should come back in November for a live aircraft capture demo. Fortunately all hands went up, which I was quick to point out to Dr. Buettner. He muttered something about old Navy guys being mission focused.
The majority of demonstrations focused on communications equipment ranging from very secure high bandwidth line of sight to satellite up and down links. Although there was a schedule, the schedule was done primarily to prevent frequency interference so demonstrators had a clean hour or two. Most of the demos went on all day as attendees walked from one tent to another or to remote locations on the base.
Ball Aerospace highlighted geospatial technology. Ball had helicopter flying overhead carrying its Flash liDAR system downloading imagery and 3D data.
For those of you not familiar with Flash LiDAR, it is what the name implies. Rather than a raster point scan the Flash LiDAR shoot all points at once. That permits the union of other data such as full-motion video with the 3D data of the Flash LiDAR. Therefore, 3D video on the fly. Their field of view is was a relatively narrow but engineers are working to widen it.
Outside the two main buildings were numerous companies set up under pop-up canopies ranging from Lockheed Martin and Harris with high-end communications gear.
Shown here are two battery powered UA’s. The helos with installed video cameras have loiter times of up to 45 minutes. There were many examples of wireless handheld com gear and high bandwidth Line of Sight transmission devices such as the example below.
There was a demonstration of paint-on antennas that turn trees or wall into an antenna and very compact fuel cells shown here.
ITT had a field demonstration of a two-way audio/video link designed for corpsman operating in remote locations. The corpsman wore a vest that contained mics, earphones and a video camera (the white device on this man’s vest). The entire system was very light and unobtrusive. It permitted multiple corpsmen to communicate directly with mobile field locations or even a specialist in a hospital. The doctor could see exactly what the corpsman was seeing and give the corpsman directions real time and hands free. This also permitted the doctor to make advance preparations to receive the patient when he was medevaced.
All during the field exercise each corpsman was tracked via GIS on an image base map. The tracking and communications were never lost even though the corpsmen were traveling behind hills with no line of sight to the mobile bases. This was accomplished through a system of local and satellite communications that reached back to Reston, Virginia. I could see that this would be beneficial for domestic first responders as well as the military. The quality of the video being sent from the corpsman was extremely good and the GIS display at the mobile base station tracked their movements very accurately.
Camp Roberts is unique in that it’s not a “sound clip” marketing bombardment like most trade shows. Since attendance is by invitation only, marketing is discouraged. What does happen are informal and in-depth discussions between field operators and engineers. Attendees get a chance to see equipment in action and exchange ideas freely. I felt lucky to be invited and hope that I can do some small part to help our troops accomplish their missions.
A few months ago, I wrote a little about ArcGIS Explorer (AE), a free GIS viewer from Esri. It’s a nice tool for non-GIS users who want to view GIS data. Looks like another feature is creeping into AE to make it a bit more powerful. Bern Szukalski, product strategist and evangelist at Esri, blogged earlier this week about new functionality in AE that will allow direct GPS support. In other words, you can connect a GPS receiver (Bluetooth or otherwise) to a device running AE and be able to visualize and record GPS data as its tracking.
Borrowing from Bern’s Blog, following is a 2D map as he was driving, showing the waypoints and tracks as he was moving. He said he set AE to collect a GPS point every 10 seconds, centering the map as he moved. GPS waypoints and tracks are stored as notes.
(Click to enlarge.)
The next screen shot shows his path in 3D. Green represents GPS points/paths collected by mouse click. Yellow represents GPS points/paths collected at 10-second intervals.
(Click to enlarge.)
Bern blogged that he was using a borrowed $18 USB GPS receiver in this example. Don’t pay much attention to the accuracy (or inaccuracy) of the GPS positioning. He could have just as easily connected a sub-meter or centimeter-level GPS receiver (outputing NMEA 0183 messages) and had enough precision to accurately position the center of a 6-inch water meter cover plate on the sidewalk. That’s where this is headed, folks.
A Quick Note on the Annual GITA Conference
I didn’t attend the annual GITA (Geospatial Infrastructure Technology Association) conference this year, but I received several reports that this was the last GITA annual conference. That’s pretty sobering (but not surprising), given that it was the 34th such conference that started in the late 1970s. I blogged last year that I thought this years was going to be a really tough one because it wasn’t co-locating with another conference as it was last year with ACSM (American Congress on Surveying and Mapping). Although the demise of the GITA annual conference was predictable, it’s still sad to see it go. Last year, I thought the technical presentations were quite good and clearly demonstrated a need for continuing promoting and developing geospatial apps in the world of infrastructure. Without the GITA conference, I wonder where these folks will go to share their knowledge and experiences. I’d like to reiterate that there are too many niche conferences related to GIS. GIS folks can’t afford the time or expense, and neither can GIS sponsors/vendors, to attend three different small GIS conferences in a 90-day window. What I wrote a year ago is just as relevant today.
Let’s discuss conferences for a minute
As good as the content was for both the GITA and ACSM conferences, the attendance was horrible. If there were 1,000 people there (for both), I’d be surprised. At this pace of decline, something’s got to give. I attended the annual GITA conference in Seattle in 2008. If I recall correctly, there were about 1,400 attendees. This year, in 2010, there were maybe half of that including exhibitors. Next year, the GITA conference is operating as a stand-alone conference in a suburb of Dallas, Texas. I predict it might be even worse than this year. The ACSM annual conference is not doing any better, but rumor has it will co-locate in 2011. The two conferences won’t be co-located next year. It’s a time for conferences to start working together. Size Matters
It’s a vicious cycle. The fewer attendees there are, the less interested vendors are in exhibiting and sponsoring the event. Each year, attendance erodes until it doesn’t make sense any longer. Now is the time for conference consolidation, especially in the GIS industry. GIS is tough to segment because it stretches across so many industry boundaries. In April alone, there was the GIS-T (GIS in Transportation) conference in West Virginia, the GITA/ACSM co-located conference in Phoenix and the ASPRS (American Society for Photogrammetry and Remote Sensing) conference in San Diego. All of these are small conferences that are becoming increasingly difficult to justify, financially, for both the operators and the attendees. I can safely say that attendees and vendors certainly would prefer to attend one conference in one location that includes GIS-T, GITA and ASPRS rather than three separate conferences spread out all over the US. They need to consolidate at the same time in a single location.
I suppose the demise of the annual GITA conference is part of the consolidation I wrote about. Being accelerated by the current economy, people will just stop attending some conferences and pick/choose the conference(s) they feel fit their needs the best.
Upcoming Events/Publications:
Following are a few upcoming events you might be interested in:
Webinar: April 21st. “LightSquared and GPS: Our Story So Far”. I’ll be participating in a moderated discussion about this issue. If your organization relies on GPS, I strongly encourage you to register. If you aren’t available during that time, register anyway and you’ll be provided a link to view the webinar at a time that’s convenient to you.
Space Weather Workshop:April 26-29. I’ll be presenting at this conference and blogging about what I hear in order to keep you informed about space weather as the next solar cycle warms up.
Western Forester: April issue. Look for my article and accompanying articles on Lidar, laser rangefinders, GPS and other emerging technologies that concern the forester and other natural resource professionals.
In the early 1990s, I recall being tasked with training a group of foresters on how to use a new-fangled handheld data collector the company I worked for had developed, along with various pieces of software on it for traversing, timber cruising, vegetation surveys, profiling, etc. Being fairly young and somewhat inexperienced, I didn’t fully understand the challenge of trying to convince a group of seasoned foresters to put away their pencils and “Rite in the Rain” tally cards and pick up an electronic gizmo in which they punched in their cruise plot info, traverse bearings, and various other pieces of field data. Of course, being involved in the development of the new-fangled handheld data collector, I thought it was the best thing since sliced bread. Who could deny the value of error-checking to check for typos, graphic plot of traverses, and no transcribing back in the office?
It’s too bad none (of mostly none) of the foresters in the room felt the same way.
“I see how it will help the office people, but what’s in it for me?” questioned one.
“It takes longer for me to punch it in the data collector than it does to write it down,” argued another.
Upon sensing the building resentment, the HFIC (Head Forester In Charge) stood up in front of the room full of 40 or so foresters and said, “Well, folks, this is the direction we are going, so you need to get with the program.”
Eventually, most of them adopted the new technology and some even embraced it. But some of the more technologically-resistant folks would go as far as using “Rite in the Rain” paper to record data in the woods only to return to their truck and enter it into the data collector. However, I believe after a period of time they became quite adept at data entry in their truck, so much so that the data collector eventually made its way into the woods with them.
That was 20 years ago. The 80386 was the mainstream computer CPU, e-mail was still a novelty, websites were few and far between, and a mobile phone was about the size of lunch box.
DuraRite “Rite in the Rain” Pocket Notebook
Since that time, it seems like the forester has been bombarded with one mind-bending technology after another.
Sorry to break the news to you, but technology is not settling down anytime soon. Following is a taste of where I think some of the technology is heading. In this issue, you’ll also read from my colleagues their take on the various technologies they work with on a regular basis.
GPS
Of course, GPS is close to my heart as I have written for GPS World magazine for many years and have been involved with GPS for more than 20 years. My first 10 years in GPS were spent developing GPS mapping products while the past 10 years have been spent as a power user of all sizes and shapes of GPS receivers, from ultra-miniature receivers giving mediocre accuracy to some of the highest -precision receivers ever made.
Since GPS has been around a long time, you may think that is has reached a level of technological maturity. In some respects, you would be right. It’s been used by foresters since the late 1980s, albeit it has evolved significantly since then.
In the early 1990s, GPS mapping receivers used for forestry were backpack configurations with handheld data recorders. WAAS didn’t exist, DGPS/beacons didn’t exist, Bluetooth didn’t exist, RTK Networks didn’t exist, and Selective Availability (SA) was active. SA meant that GPS autonomous accuracy (without any sort of correction) was about 100 meters. To improve accuracy, users had to post-process their GPS data using GPS base-station data. Public GPS base stations were virtually non-existent, and the Internet access was not commonplace, so most folks had to install, manage, and maintain their own GPS base stations.
In May 2000, one of the most significant events in GPS history took place. The U.S. Government turned off SA. Overnight, the autonomous accuracy of GPS receivers increased ten-fold. It was never turned on again, and years later it was announced the feature wouldn’t be designed into future GPS satellites. It is gone forever.
Since then, GPS availability and accuracy has increased due to a number of GPS system advancements as well as GPS receiver advancements. The price of GPS receivers have also dropped significantly. In 1990, a GPS receiver designed for 2-5 meter accurate mapping was priced at more than $10,000. Today, a sub-meter accurate GPS receiver can be purchased for under $2,000. That trend is going to continue. In fact, GPS is going to change a lot more in the next 10 years than it has in the last 10 years.
Last year, the U.S. government launched a new generation satellite (model IIF) that adds another signal for civilians called L5. Once enough satellites are in orbit broadcasting L5 (as soon as 2015), you’ll likely see very inexpensive, high-accuracy GPS receivers.
The beauty of the L5 signal is that it’s supported by other GPS-like systems such as Europe’s Galileo. The European Union is scheduled to launch its first two operational satellites this summer with the second pair scheduled for launch in early 2012. The first 18 Galileo satellites are projected to be in orbit by 2015. Since Galileo satellites use the same L1 and L5 frequencies as GPS satellites, a receiver designed for GPS is easily designed for Galileo, too. One advantage of a GPS/Galileo receiver is that you’ll have more satellites in view, and for foresters working under tree canopy or on steep terrain, this will make mapping a lot easier and quicker. For example, today you might have 6-7 GPS satellites in view while you’re in the woods. With future GPS and Galileo satellites, you might have 12 or 13 satellites in view.
GPS receivers are becoming cheaper, better, and faster. Similar to personal computers, GPS receivers have declined in price and will continue to decline in price. Don’t be surprised if you see high-precision GPS receivers for mapping being sold for $100-200 in the future. WAAS is going to support L5, too. Today, the best accuracy you can get from WAAS is around two feet. Once WAAS supports L5 (around 2020), it will be able to provide accuracy of around four inches to inexpensive L1/L5 dual-frequency receivers.
The Russian satellite system (GLONASS) has brought a lot to the table for surveyors and engineers in the past 10 years. In 2000, it seemed the GLONASS program was dead in the water and heading for extinction. The Russian Federation has done a fantastic job of revitalizing GLONASS to the point that GLONASS has become a standard feature on high-accuracy GNSS receivers across the surveying and engineering industries. The value of GLONASS is not accuracy, but rather availability. If you’re in the woods and having trouble tracking enough GPS satellites, GLONASS can add another 5-6 satellite signals, which can be the difference between getting a shot or not in dense tree canopy.
While GLONASS used to be a feature only offered in high-accuracy surveying receivers due to its complex design, you will start to see mid-range GPS mapping receivers utilizing GLONASS. It’s also likely you’ll see consumer GPS receivers offering GLONASS as well because in the past couple of months, two of the GPS chipset companies introduced GPS/GLONASS chips for the consumer market.
Bottom line: GPS receivers are going to get significantly more accurate, cheaper, and work in more places than they do today.
Satellite Imagery
At the Esri conference la
st summer, Lawrie Jordan, Esri’s director of Imagery Solutions and founder of ERDAS, said this is the most exciting time to be involved in imagery in his 40-year career.
Commercial satellite imagery quality and availability is the best it’s ever been. It wasn’t that long ago that five-year-old, three-meter-pixel resolution, black/white satellite imagery was the norm. Today, GeoEye, DigitalGlobe, RapidEye, and Spot Image are delivering an amazing amount of digital imagery at even more amazing resolutions on a regular basis. Jordan predicts that in less than five years, every square inch of the Earth will be imaged (by satellites) constantly. He said we are already half-way there.
There is no better technology than satellite imagery for capturing the devastating impact of large-scale natural disasters such as the March 11, 2011, earthquake/tsunami in Japan.
The following image (half-meter resolution) of Miniami Sanriku Cho, Japan, was captured by the GeoEye-1 satellite on November 15, 2009, prior to the earthquake/tsunami.
Courtesy: GeoEye
The next image (one-meter resolution) was taken on March 12, 2011, a day after the fifth strongest earthquake in recorded history struck off the coast of Japan, creating a massive tsunami that caused devastating flooding and resulted in extensive infrastructure damage and loss of life.
Courtesy: GeoEye
The following one-meter resolution image was shot by GeoEye’s IKONOS satellite on March 23, 2011. According to GeoEye, this is the Indian Gulch fire burning near Golden, Colorado. As of March 24, the fire had consumed 1,500 acres and was 25 percent contained. GeoEye says this type of imagery may be used to assess and measure damage to forest and other types of land cover — especially when compared to a false-color image of the same area.
Courtesy: GeoEye
Bottom line: Commercial satellite imagery is becoming more readily available and at higher resolutions than ever before. Look for that trend to continue.
Lidar
Lidar (Light Detection and Ranging) is a remote sensing technology that is sometimes referred to as 3D scanning. Traditionally, LiDAR is thought of as an airborne technology with a scanner mounted in an aircraft that can map huge swaths of ground, collecting elevation data in order to create a digital elevation model (DEM) for topographic surveys and other types of analysis. While collecting the data is relatively quick (albeit expensive), a huge amount of data is collected and must be processed.
According to the US Geological Survey (USGS), two problems have hindered Lidar for scientific applications beyond creating bare-earth DEMs.
The high cost of collecting Lidar data.
The steep learning curve on research and understanding how to use the entire point cloud.
While airborne Lidar has been around for quite some time, terrestrial (land-based) Lidar has made a strong push in recent years, and has even made its appearance on mainstream television (Crime Scene Investigation – CSI on CBS, 2005). Working on the same concept of 3D scanning, terrestrial Lidar is not used from thousands of feet in the air looking down, but rather on a tripod scanning a room, or scanning a bridge from 200 feet in the distance.
Courtesy: Wikipedia
Personally, I coordinated a 3D scanning project many years to create a 3D model of a wrecked SAAB 9000 as part of an accident reconstruction project. The process of scanning was very quick. It was completed within a couple of hours. The process of creating a deliverable (this was circa. 2003), however, was another story. It was a very labor-intensive project that took weeks. Today, software to create a deliverable from these big “point cloud” files has improved dramatically and more increasingly, third party software developers are creating software tools that assist users in working with these data sets.
Terrestrial 3D scanners first started making their appearance in the land surveying and civil engineering professions. 3D scanners are an efficient way to create complex as-built maps such as in refineries.
Courtesy: Wikipedia
They still have somewhat of a steep price tag today, but they were especially expensive when they were first introduced, well over $100,000 at that time.
But terrestrial 3D scanning is hitting its stride and finding its way into other industries besides surveying and engineering. Yes, even forestry. Albeit in its early stages of development, 3D scanners are being hauled into the woods.
Take a look at the following illustration courtesy of TreeMetrics of Ireland.
Courtesy: TreeMetrics Ltd
According to TreeMetrics, millions of points are collected with each 30 meter scan. After downloading the scan data, software filters irrelevant data and creates a 3D profile of each tree. The DBH, height, taper, straightness and volume are calculated for each tree. Trees that weren’t scanned due to heavy branches or other obstructions are modeled. Stem data files are then produced from which simulation models can be developed that will be used to estimate the product value before a tree is harvested. If harvesting is not done at that time, data is recorded and can be compared to future scans to monitor growth and health.
Bottom line: 3D scanning, especially terrestrial 3D scanning, is a technology you’ll see in the not-so-distant future, maybe even in the woods. Prices of 3D scanning equipment will continue to decline while software to handle the massive point clouds will continue to become more powerful.
GPS, satellite imagery, and Lidar are only three of a number of advancing technologies that foresters will see working their way into their toolkit. Mobile phones are also advancing at a rapid pace, becoming significantly more powerful and performing many more tasks than just a phone. The more advanced mobile phones have a GPS chip built inside as well as street maps and aerial photos a la Google and Microsoft. If you look back at mobile phones 10 years ago and compare them to today’s phone, it’s hard to imagine where they will be 10 years from now. They could quite possibly be the central piece of office equipment for all your communications and document management.
My fellow geospatial editor, Art Kalinski, wrote about BIM (building information modeling) earlier this week in the GeoIntelligence Insider newsletter. I’ve touched on the subject before. All too often we think of GIS as it relates to outdoor infrastructure: street maps, utility systems, parcel maps, timber harvesting, land management, environmental management, etc.
Last summer at the Esri Surveying and Engineering Summit, I attended a talk presented by Stuart Rich, chief technology officer of Penobscot Bay Media, LLC. He presented on understanding, documenting, and building systems to support spatial data infrastructure’s security requirements as well as initiatives to move GIS inside the building footprint.
He said he was involved in using terrestrial LiDAR inside buildings to collect massive amounts of data. So much, in fact, that “the value of measurement is trending very close to zero” using very high-volume data collection at 250,000 points/second.
Stuart’s Factoid: Only 16% of cities are mapped, with a big vacuum being building interior maps in urban areas.
He also discussed the lack of attention to underground infrastructure mapping.
Another example of BIM detail, as provided in Art’s article, is a building wall which, in most GIS, if it exists at all, is a single polyline, maybe two polylines in rare cases. Thinking in a GIS sort of way, a building wall ”could contain more than six layers of data: paint, drywall, framing, blocking, fire stops, insulation, etc.” Think about this for a minute. Imagine how the quality of decisions would improve if the building owner was considering renovating his building and had this sort of information and software tools available. The decisions about which walls to leave or take down and future layout, for instance, would likely change if this information was readily available.
Honestly, for building design, and most kinds of design for that matter, CAD isn’t the right tool if you think about it. It doesn’t have the database or analysis tools behind the various points, lines, and polygons to make the best decisions. This is the foundation of the GeoDesign concept being promoted these days.
Although I didn’t set out to write about GeoDesign, it’s very fitting. According to Wikipedia, “GeoDesign brings geographic analysis into the design process, where initial design sketches are instantly vetted for suitability against a myriad of database layers describing a variety of physical and social factors for the spatial extent of the project. This on-the-fly suitability analysis provides a framework for design, giving land-use planners, engineers, transportation planners, and others involved with design the tools to leverage geographic information within their design workflows.”
Of course, as Stuart mentions and as I’ve written about before, a highly related topic is underground infrastructure (sewer, water, electric, gas, telecom). That’s a whole other subject and one that I’m close to as I spend quite a bit of time working with landscape architects who deal with underground infrstructure on a daily basis in their projects. For them, as opposed to “what’s inside the wall,” a landscape architect has to ask “what’s under the ground.” If he or she doesn’t know until the construction crew starts tearing down and digging, then the project risk increases substantially.
A good example and story I read this week was a short interview that Directions magazine published about the San Bruno gas pipeline explosion which killed nine people. You can read the interview here. Essentially, it’s a lesson in spatial data management with respect to underground infrastructure, with spatial data accuracy being the primary theme.
Data, Data, Data
In the world of real estate, it is said the three most important features of real-estate property are location, location, and location. I think you can say that the three most important feature of a GIS are data, data, and data. It’s not the software tools we are lacking, it’s the data. That’s why revenue from GIS data over the past eight years has grown at a compound annual growth rate (CAGR) of ~15 percent, while GIS software has grown considerably less, according to research firm Daratech, Inc.
Where Is the Data Coming From?
Data collection technology is changing rapidly. Look at two key sources of geospatial data: remote sensing and GPS. Remote sensining, in particular, is well-suited for building interior data collection.
At the same Esri Surveying and Engineering conference I mentioned above, Lawrie Jordan, director of Imagery at Esri, said that this is the most exciting time to be involved in imagery during his 40-year career.
Commercial satellite imagery quality and availability is the best it’s ever been. It wasn’t that long ago that three-year-old, one-meter-pixel resolution, black/white imagery was the norm. Today, GeoEye, DigitalGlobe, RapidEye, and Spot Image are delivering an amazing amount of digital imagery at even more amazing resolutions. Jordan stated that in less than five years, every square inch of the Earth will be imaged (by satellites) constantly. He said we are already half-way there.
Another form of remote sensing that’s busting at the seams is 3D scanning (terrestrial LiDAR). We’ve seen a lot of development in 3D scanning over the past 10 years. The equipment used to be pretty expensive, but the prices are coming down as the technology gains acceptance. I recall using the technology a number of years ago (circa 2003). I was tasked with an accident reconstruction project. Part of the task was to create a 3D model of a wrecked automobile. Traditionally, one would use a surveying total station and measure shot-by-shot at key points on the automobile. Even measuring 1,000 points on the automobile wouldn’t result in enough data points to create a reasonable 3D model. We decided to use a 3D scanner. We were able to scan the automobile in under two hours and collect a tremendous amount of detailed data.
The good news is that we had a tremendous amount of detailed data to work with. The bad news was the same, we had a tremendous amount of detailed data to work with. I think it took us four weeks to produce a deliverable from the data. However, keep in mind that this was nearly eight years ago and software tools have come a long way since then (Safe Software, Leica Geosystems, Trimble, Topcon, all have software tools for dealing with 3D scan data), so the process in producing a deliverable today is more efficient.
I’ve written and said this many times over: geospatial data fuels the GIS software engine. Esri and other GIS software developers are making very powerful GIS engines. In fact, the GIS software engines far exceed the quality of the geoespatial data we have to work with. BIM is a great example of that. There’s a substantial lack of BIM data, but with 3D scanning and other geospatial data collection technology advancing rapidly today
, that will change. GIS will move indoors.
![FIGURE 6. Gain pattern of the patch antenna as measured by the measured C/N0 at all elevation angles as a function of antenna distance from body. Elevation angles [0º, 90º] have azimuths [180º, 360º], while elevation angles [90º, 180º] have azimuths [0º, 180º]. Jared B. Bancroft, Valérie Renaudin, Aiden Morrison, and Gérard Lachapelle](https://stage.globalpositioningnews.com/wp-content/uploads/2012/02/Inn-Fig6.jpg)
![FIGURE 9. Gain pattern of the quadrifilar antenna as measured by the C/N0 of all measurements as a function of antenna distance from body. Elevation angles [0º, 90º] have azimuths [180º, 360º], while elevation angles [90º, 180º] have azimuths [0º, 180º]. Jared B. Bancroft, Valérie Renaudin, Aiden Morrison, and Gérard Lachapelle](https://stage.globalpositioningnews.com/wp-content/uploads/2012/02/Inn-Fig9.jpg)
