Geneq Inc. has announced the SXPad 1000P, a rugged handheld GPS data collector, which the company says is low-cost.
The SXPad 1000P is suitable for mobile GIS users in applications ranging from water, electric, gas utilities, transportation, mining, agriculture and forestry.
The high-performance 1000-megahertz device is designed to give professionals the power needed to work with maps and large data sets in the field. Its waterproof seal (IP67) and surviving 5-foot (1.5-meter) drops to concrete make the SXPad 1000P ideal for the outdoors. Its 3.7-inch color touchscreen (full VGA) is sharp and is sunlight readable.
Standard features include a battery life of more than 10 hours on a charge, 8-GB internal storage, slots for MicroSD cards and SIM cards as well as Windows Mobile 6.5.
The SXPad 1000P offers features typically seen in more costly mobile devices, the company said. These include 3.5G cellular modem, Wi-Fi, Bluetooth, video capture, a 5-megapixel camera and an internal GPS receiver.
The SXPad 1000P is optimized for GPS/GIS field data collection using its 1-3 meter accuracy internal GPS receiver or one of Geneq’s high-performance SXBlue GPS receivers for sub-meter and centimeter-level accuracy.
SBG Systems Chief Technology Officer Alexis Guinamard discusses the company’s full line of inertial sensors at Intergeo 2016, which was held Oct. 11-13 in Hamburg, Germany. SBG Systems featured its mobile mapping, aerial survey and georeferencing solutions at the trade fair.
Don Jewell passed away unexpectedly on Oct. 12. For more than nine years, Don wrote the Defense PNT monthly e-newsletter column for GPS World, after a distinguished 30-year career in the U.S. Air Force, retiring as Deputy Chief Scientist for Air Force Space Command with the rank of Lieutenant Colonel. A celebration of his life was held Oct. 20 in Colorado Springs.
Born in Louisville, Kentucky, Don earned a bachelor’s degree in political science from the University of Kentucky and a master’s degree from the University of Oklahoma. He served in the U.S. Air Force as an aviator, navigator and space subject matter expert, and completed two Command assignments at Schriever Air Force Base.
His involvement with GPS began in 1978, either as a test system evaluator or user. As Politico-Military Affairs Officer in the Reagan White House, he worked with foreign embassies making critical export control decisions concerning sophisticated military hardware and software.
After the Air Force, Don worked seven years as senior space executive at Motorola and General Dynamics and as senior VP at Infofusion.
He worked at the Institute for Defense Analyses (IDA) as a member of several advisory committees to the Department of Defense and U.S. government: the GPS Independent Review Team (IRT), Space Programs Assessment Group for SMC, Independent Assessment Team for WAAS and as Co-Chair of Military Critical Technologies Program for Space.
A close friend said, “Don was a real pillar for the PNT community and consummate spokesman for the truth, always offering constructive criticism where needed. An exemplary personality who always ‘did the right thing.’”
Another colleague remembered, “Don was a key player in all tasks undertaken in response to the Commander Space Command. One of his many significant roles was as key IRT debriefer of warriors returning to the U.S. through Ft. Carson following operational deployments, to get candid inputs on what shortfalls in PNT they had using GPS to execute their missions, so that Don could make sure DoD leadership didn’t get complacent in management and operation of GPS.
“His use of PNT as a vehicle for constant improvement was driven by Don selflessly serving our national security, helping our soldiers, sailors, marines, airmen and others operating in harm’s way to serve our country well in his passionate and very candid role with his ‘constructive criticism’ counsel to Air Force and DoD leadership to assure the troops’ mission success, returning home safely often after intense combat. A tragic loss to our Nation, as he did this for many years.”
“To think that all these billion-dollar companies, and the start-ups as well, depended to such a great degree on a ubiquitous utility that only became available on a global basis because of a seemingly insignificant, but in the end, deadly navigation error. Add to this the naked aggression and paranoia of the former Soviet Union and the benevolence and caring of a legendary U.S. President, and you have the beginnings of a tale that has changed our world forever, and whose final chapter may never be written.”
Don was active in the Military Division of the Institute of Navigation (ION). From 2010–2015, he helped assemble and co-chaired the Warfighter Crosstalk Panel in the Joint Navigation Conference (JNC); this was and remains today one of the most interesting and informative sessions of that conference, focusing on needs of military and first responder users for PNT.
Don regularly led weekly bible study meetings for more than 20 years and was recently appointed as president of Christ the King Lutheran Church.
Modern tower cranes can reach a height of more than 200 meters. They operate in a complicated, chaotic and constantly changing environment. This creates obstacles for the crane operator: poor visibility and dead angles — places the operator can’t see.
Aiming to solve the problem is the Augmented Crane Navigation System (ACNS) project, which provides innovative intelligent operation of tower cranes on construction sites through the integration of highly accurate navigation receivers and a powerful processor unit.
Polish researcher Piotr Krystek took home the DLR Special Prize from the European Satellite Navigation Competition (ESNC) for the ACNS, which is designed to increase efficiency and safety at construction sites.
Using the ACNS, the position of the crane elements can be determined and oriented using four to five low-cost yet highly precise Galileo or GNSS receivers. The central processor calculates the best possible route for load management. In addition to the position values of the various satellite navigation receivers, the digital model of the physical structure or Building Information Model (BIM) is used. Using a head-up display, the visualization is projected directly onto the crane operator’s field of view to enable easy and precise navigation.
The ACNS has a modular design and can be mounted on the crane easily; this includes the retrofitting of existing cranes.
The project is still in the concept phase. To implement the idea, the market must be explored and feasibility studies carried out with cranes in collaboration with crane manufacturers, Krystek said.
The ACNS also could be transferred to other construction machinery and commercial vehicles, Krystek said. As one of the leading economic sectors, the construction industry can benefit immensely from GNSS-based solutions.
Krystek was inspired to pursue the project because of the tower cranes visible from his window in Krakow — along with the availability of low-cost RTK receivers. He is also inspired by the trend to automate everything that can be automated, such as self-driving cars.
Fugro’s laser airborne depth sounder (LADS) technology is being deployed in New Zealand to assist in relief efforts following the damaging 7.9 magnitude earthquake near Christchurch on Nov. 14.
At the request of the New Zealand Government, the Royal Australian Navy LADS flight is to conduct a rapid hydrographic survey of the seafloor in the coastal margins of the north east coast of the South Island.
“We will fly over the area and collect hydrographic survey data, which will reveal what has happened below the waterline, and identify any shifts in the ocean floor which mariners need to be aware of,” explained Flight Lieutenant Commander Susanna Hung, who is serving as the mission’s commanding officer.
The navy’s airborne lidar bathymetry (ALB) system has been developed by Fugro for safe, high speed and cost effective surveys of shallow coastal areas. Under a long-term contract to the RAN, Fugro provides the LADS technology, a de Havilland Dash 8-202 aircraft and support services.
Fugro’s LADS technology is being deployed following the Nov. 14 New Zealand earthquake.
The airborne survey equipment is operated by navy personnel from the main cabin of the aircraft to rapidly collect high resolution data of the seafloor. Fugro’s system incorporates sophisticated sensors that utilize a high-powered laser, innovative scanner and receiver optics technology.
The survey tool complements traditional hydrographic survey methods (such as hull-mounted multibeam echo sounders) to support nautical charting and coastal zone management applications in the nearshore/shallow water environment. The speed of deployment and safe operating capability make it an ideal solution to confirm the safety of navigation and locate new hazards such as is now required in the earthquake affected area.
“The New Zealand deployment by RAN LADS is an excellent example of how our innovative technology can assist in the safety of navigation and management of the marine environment,” said Paul Seaton, Fugro’s regional business development manager.
Reyax Technology, an industrial and telematics systems provider for aftermarket telematics, has launched a new industrial router platform that incorporates cellular, short range and GNSS modules from u-blox.
The RYW2000 4G LTE and Wi-Fi hot-spot router platform uses the EVA-M8M, a tiny concurrent GNSS module, a TOBY-L2 cellular LTE module that offers throughput of up to 150 Mb/s with LTE Cat.4, and an ELLA-W131 2.4-GHz Wi-Fi and Bluetooth module.
“We selected u-blox modules because of their market-leading performance, excellent environmental tolerance characteristics and the fact they develop all of their technology in-house,” said Ritchie Chang, general manager of REYAX Technology. “Our RYW2000 router platform is designed for industrial and telematics applications where performance, reliability and conformance to changing environmental conditions are all critical to the success of our product.”
Front and back of the Toby L2 module.
The new router platform RYW2000 includes a router platform card for Industrial and telematics applications and measures only 50.95mm x 30mm. Its operating condition and power are DC 3.3V-5.5V.
Ming Chiang, country manager of u-blox Taiwan explains, “This is another example of our on-going collaboration with REYAX Technology and we are excited they have chosen to incorporate three of our modules into their RYW2000 product. Together we have a shared vision for the promotional of IoT and M2M technologies to benefit many industries and applications.”
GPS-enabled devices render large amount of assistance to a country’s armed forces on battlefields. In the modern-day scenario of combat, the need to be technically advanced and the ability to achieve precision strike with minimum self-loss are taking center stage.
This has resulted in greater use of GPS-guided devices and weapons by soldiers, which are considered in a new report by Research and Markets.
In Global Military GPS Device Market 2016-2020, analysts forecast the global military GPS device market to grow at a compound annual growth rate (CAGR) of 3.69 percent between 2016 and 2020.
The report covers the present scenario and the growth prospects of the global military GPS device market for 2016 to 2020. To calculate the market size, the report considers the expenditure of each of the three regions (Americas, EMEA and APAC) to acquire these military GPS devices for enhanced performance of warfighters.
The report has been prepared based on an in-depth market analysis with inputs from industry experts. It covers the market landscape and its growth prospects over the coming years.
The report also includes a discussion of the key vendors operating in this market.
Key questions answered in the report include:
What will the market size be in 2020 and what will the growth rate be?
What are the key market trends?
What is driving this market?
What are the challenges to market growth?
Who are the key vendors in this market space?
What are the market opportunities and threats faced by the key vendors?
What are the strengths and weaknesses of the key vendors?
Companies mentioned include:
BAE Systems
Lockheed Martin
Northrop Grumman
Raytheon
Rockwell Collins
Garmin
Harris
Thales
Buyers can request one free hour of the analyst’s time when purchasing thye market report. Details are provided within the report.
Trimble has introduced itsDPS900 Machine Control System for Dynamic Compaction, a dedicated 3D system for dynamic compaction applications such as airports, roads and large structures.
The DPS900 increases worker safety by eliminating the need for surveyors to work in close proximity to large machines. The number of drops per location and the depth of the hole can be accurately and automatically tracked and recorded, reducing errors from a manual reporting method.
In addition, the DPS900 system reduces setup time for each drop location, which can increase production and reduce costs.
Saphibeat Technologies’ new Adventure Monitor PhiPAL can save lives of outdoor enthusiasts by recognizing when an accident has taken place.
PhiPAL uses a proprietary machine-learning algorithm for accident recognition. If the user is unconscious, PhiPAL automatically sends a distress message with GPS coordinates to teammates and first responders through a cellphone or satellite connection.
PhiPAL uses an activity monitor mounted on or integrated into the user’s sports helmet.
The project, Drones2GNSS, also took home the Special Prize offered by the European GNSS Agency (GSA).
Space Geomatica Ltd.’s Tripolitsiotis Achilles joined with Panagiotis Partsinevelos, SenseLab Research, Technical University of Crete, to develop Drones2GNSS.
In the tracking procedure, the engineer with the surveying pole might move around, yet the UAV tracks in real time and provides the GNSS coordinates.
Drones2GNSS includes a prototype drone equipped with a highly accurate GNSS receiver and a camera/laser measuring system that retrieves the coordinates of custom surveying poles featuring Wi-Fi, a prism and a target marker.
The team’s image processing algorithms and error correction techniques provide real-time, centimeter-level coordinate estimation and can simultaneously measure multiple moving surveying poles.
The processing is performed on-board the UAV without any ground-based hardware. In this way, Drones2GNSS provides a fast, reliable, cost-effective alternative for absolute coordinate positioning in obstructed environments where GNSS fails. It can cover multiple targets, including cars, people and vessels.
It also offers a basis for other related challenges, including UAV GNSS networks, indoor positioning and error mitigation.
“Although Galileo Initial Services are expected to enhance the accuracy of existing solutions, Drones2GNSS proposes an off-the-shelf application that uses European GNSS (Galileo, EGNOS) as the primary means of positioning,” Tripolitsiotis said. “As GNSS signals are degraded in obstructed environments by skyscrapers, vegetation and geomorphology, our project proposes using drones as intermediate carriers of high-precision GNSS signals that can then transfer the geolocation accuracy to the ground.”
Drones2GNSS relies heavily on multi-constellation GNSS signal, which is where Galileo will make the difference. “As current constellations like GPS and GLONASS have proven inefficient in confronting the aforementioned surveying problem, the sector continues to rely on traditional surveying techniques,” Tripolitsiotis said. “However, with the launch of the Galileo era and the utilization of the Drones2GNSS approach, we can now provide surveying engineers a cost effective, accurate and fast positioning solution.”
Chinese car navigation systems company Skypine has adopted Furuno’s GPS receiver with a dead-reckoning function.
Furuno Electric, headquartered in Nishinomiya, Japan, said its receiver GV-86 has been adopted for use in the car navigation platform designed and produced by Skypine — a major car electronics manufacturer in China.
GV-86 will be installed in the car navigation systems designed for major automotive companies, not only in Japan but also around the world and the specialized companies, which Skypine contracted.
Furuno’s GV-86 is used by many automotive customers requiring high quality and reliability. Additionally, thanks to the dead-reckoning function, GV-86 achieves high-accuracy performances in deep urban canyons where the accuracy of GNSS-only positions could be reduced.
Skypine’s car navigation systems (left); Furuno’s Multi-GNSS Receiver Chip eRideOPUS 6 and GPS+DR Receiver Module GV-86.
Understanding the differences between the North American Vertical Datum of 1988 and the new 2022 Vertical Reference Datum
My Survey Scene columns have focused on procedures and routines for establishing GNSS-derived orthometric heights. My last column focused on analyzing NGS’ GPS on BM data set that is used to make National Geodetic Survey’s (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 the North American Vertical Datum of 1988 (NAVD 88) and the new 2022 Vertical Reference Datum. As I emphasized, 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.
Large relative differences in residuals between neighboring stations provided examples of stations that should investigated based on different reasons: No. 1, a weak NAVD 88 is leveling network design in the region; No. 2, the station’s published height attribute code implies that the station was not rigorously adjusted into the NAVD 88; and No. 3, station pairs have different adjustment dates indicating a possible adjustment distribution correction issue or movement.
It was mentioned that NGS has a program called “GPS on Bench Mark” to support users that occupy bench marks with GNSS equipment. It was also mentioned that in addition to participating in the NGS’ GPS on Bench Mark program, all geospatial users should participate in the NGS 2017 Geospatial Summit, which will be held in April 2017 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.
This column will briefly address NGS’ plans to replace the North American Vertical Datum of 1988 in 2022; and, in my opinion, why GNSS users need to obtain a better understanding of the differences between the NAVD 88 and the new 2022 Vertical Reference Datum.
I have highlighted three FAQs that I believe users should learn more about. (See box titled “Excerpts from NGS’ New Datums FAQs, below.) Under the FAQ “Why is NGS replacing the North America of 1983 and the North America Vertical Datum of 1988 (NAVD 88)” it states that the NAVD 88 is both biased (by about one-half meter) and tilted (about 1 meter coast to coast) relative to the best global geoid models available today.
Why is NGS replacing the North American Datum of 1983 (NAD 83) and the North American Vertical Datum of 1988 (NAVD 88)? NAD 83 and NAVD 88, although still the official horizontal and vertical datums of the National Spatial Reference System (NSRS), have been identified as having shortcomings that are best addressed through defining new horizontal and vertical datums. Specifically, NAD 83 is non-geocentric by about 2.2 meters. Secondly, NAVD 88 is both biased (by about 0.5 meters) and tilted (about 1 meter coast to coast) relative to the best global geoid models available today. Both of these issues derive from the fact that both datums were defined primarily using terrestrial surveying techniques at passive geodetic survey marks. This network of survey marks deteriorates over time (both through unchecked physical movement and simple removal), and resources are not available to maintain them. The new reference frames (geometric and geopotential) will rely primarily Global Navigation Satellite Systems (GNSS) such as the Global Positioning System (GPS) as well as an updated and time-tracked geoid model. This paradigm will be easier and more cost-effective to maintain.
How will accessing the National Spatial Reference System (NSRS) change with the release of the new datums?The NSRS will be accessed using Global Positioning System (GPS) technology that references Continuously Operating Reference Stations (CORS) and relies on a time-dependent gravimetric geoid model. This method of accessing the NSRS is a paradigm shift from accessing NAD 83 and NAVD 88 through the use of geodetic survey marks.
How can I learn more about the new reference frames?NGS will participate in and host meetings to discuss the transition from NAD 83 and NAVD 88 to the new reference frames. We will continue to update our website with events, announcements and new outreach materials, as they become available.
The “Get Prepared” section on the New Datum website explains how users can get a ready for the new datums. In this section, NGS provides a figure that depicts the approximate orthometric height change between the NAVD 88 and the 2022 Vertical Reference Datum (Figure 1).
[FIGURE 2]NAVD 88 minus NGVD 29 Datum Shift ContoursA similar difference was detected in 1929 when the NGVD 29 general adjustment was performed. Figures 3 and 4 depict the adjusted height differences between the NGVD 29 fully-constrained adjustment and a minimally-constrained adjustment. The heights of 26 tide stations were constrained in the fully-constrained NGVD 29 general adjustment. Four of the constrained tide stations have been labeled to show the differences between the east coast and the west coast of the U.S.
[FIGURE 3] Coast-to-Coast Height Differences in the National Geodetic Vertical Datum of 1929 General Adjustment – Plot AAs indicated in the plots depicting the results of the NGVD 29 General Adjustment, the difference between stations at St. Augustine, Florida, and Fort Stevens, Oregon, was 86.3 centimeters. This is similar to the trend between the NAVD 88 and NGVD 29. It should be noted that most of the original NGVD 29 leveling data were revealed, so the leveling data observed prior to 1929 were not included in the general adjustment of the NAVD 88. In 1929, the Coast and Geodetic Survey (the predecessor of the NGS) decided to constrain the heights of the 26 tide gauges and force the differences between the constraints.
[FIGURE 4] Coast-to-Coast Height Differences in the National Geodetic Vertical Datum of 1929 General Adjustment – Plot BPrior to performing the NAVD 88 general adjustment a special project was performed to evaluate possible constraints including constraining heights of various tide gauges. Regardless of which datum definition scenario was chosen, i.e., the height of one tide gauge or heights of multiple tide gauges on the east and west coasts of the U.S., the results showed that large differences between NAVD 88 and NGVD 29 heights would exist. These differences were due to many factors, such as large distribution corrections (residuals) from the NGVD 29 adjustment, better estimates of corrections applied to account for systematic errors, crustal movement, and estimating geopotential differences using real gravity values instead of normal orthometric height differences. Based on the results from the special study, NGS decided to constrain the height of one tide gauge and not force the differences between constraints. This was mainly because of the uncertainty of the heights of the tide gauges representing the same equipotential surface. The new 1988 heights are much better estimates of orthometric heights than are the NGVD 29 heights.
As part of the NAVD 88 datum definition study, NGS also compared Satellite-Derived Orthometric heights computed using the best available geoid model and ellipsoid heights with NAVD 88 leveling-derived heights. See box titled “Excerpt from 1992 report titled “Special Report – Results of the General Adjustment of the North American Vertical Datum of 1988.” As stated in the report, based on the comparison, combining VLBI-derived orthometric height difference data with leveling data in NAVD 88 would not have helped to control remaining errors in the leveling data, or significantly improved the estimates of adjusted heights in the network adjustment. The results were consistent with the accuracy statements of GEOID90. VLBI-derived orthometric heights did not show the same 1.5 m difference indicated by the LMSL (epoch 1960-78) tidal heights. Therefore, if the coast-to-coast leveling does indeed contain long-wave-length systematic errors, the errors probably are not as large as 1.5 m.
Corrections to account for known systematic errors were applied to the leveling data involved in the NAVD 88 but it is recognized that the leveling data could still have a small systematic error remaining in the data. The leveling distance from the east coast to the west coast is over 5,000 kilometers. If we assume that the leveling crew performed a setup every 150 meters, then the number of setup across the country would be over 30,000 setups. If we assume a systematic error of 0.02 millimeters, then the accumulated error could be at least 600 millimeters (60 centimeters). Although, there also could be a small systematic error in the scientific geoid model due to an undetected and/or unmodeled long wavelength error. (Of course, this statement is from the NAVD 88 Project Manager, me, and may be a little bias). At this moment, it really doesn’t matter why the systematic difference exists, just that it does and that the new 2022 Vertical Reference Datum will be established using the same process used to generate the scientific geoid models. Therefore, it is important for all users of geospatial data to prepare for the changes.
Comparison of NAVD 88 Adjusted Heights from the General Adjustment with Satellite-Derived Orthometric Heights
In a report by Despotakis (1987), discussed in the datum definition study by Zilkoski, Balazs, and Bengston (1989), numerical computations of geoid heights using several methods were compared with satellite-derived geoid heights (ellipsoid heights minus orthometric heights) at laser tracking stations around the world. Despotakis’s report states:
The numerical computations of the geoid undulations using all the four methods resulted in agreement with the “ellipsoidal minus orthometric” value of the undulations on the order of 60 cm or better for most of the laser stations in the eastern United States, Australia, Japan, Bermuda, and Europe. A systematic discrepancy of about 2 m for most of the western United States stations was detected and verified by using two relatively independent data sets. The cause of this discrepancy was not found.
The results of the 1989 datum definition report provided a possible explanation for this systematic discrepancy of 2 m in the western U.S. stations (i.e., the difference between NGVD 29 and NAVD 88 in western United States was about 1.5 m). Applying NAVD 88 heights to Despotakis’s study reduced the 2 m bias to 60 cm.
The problem with adjusting space-derived orthometric height data with leveling data is similar to the problem of using LMSL tidal heights as weighted observations in a leveling network adjustment: The uncertainties in space-derived orthometric height differences are too large to help control remaining errors in the leveling data. Space-derived ellipsoid height differences over long lines are probably more precise than leveling-derived orthometric height differences over the same distance. The uncertainties of geoid height differences used to convert ellipsoid height differences to orthometric height differences are large compared with the formal errors of leveling height differences. Several Very Long Baseline Interferometry (VLBI) stations, which were tied into NAVD 88, were included as special junction stations. The results of the final adjustment comparing NAVD 88 adjusted heights with VLBI-derived orthometric heights derived using the best available estimates of ellipsoid heights (Strange 1991) and geoid heights (Milbert 1991) are given in Figure 11.
Figure 11 indicates that the results are consistent with the accuracy statements of GEOID90. In coast-to-coast geoid height differences, the accuracy of the underlying geopotential model OSU89B (Rapp and Pavlis 1990) dictates the accuracy of GEOID90. OSU89B is believed to have a standard error of approximately 60 cm. VLBI-derived orthometric heights do not show the same 1.5 m difference indicated by the LMSL (epoch 1960-78) tidal heights. Therefore, if the coast-to-coast leveling does indeed contain long-wave-length systematic errors, the errors probably are not as large as 1.5 m. Combining VLBI-derived orthometric height difference data with leveling data in NAVD 88 would not have helped to control remaining errors in the leveling data, or significantly improved the estimates of adjusted heights in the network adjustment. As the accuracies of geoid models continue to improve, space-derived orthometric height data will be incorporated into NAVD 88 and future adjustments.
The “Get Prepared” section on the New Datum website has a “GPS on Bench Marks” option. This is where NGS recommends that you obtain accurate GNSS-derived ellipsoid heights on NAVD 88 bench marks. We discussed this program in my last column. In Addition to improving the transformation model from NAVD 88 to the new 2022 Vertical Reference Datum, occupying more NAVD 88 bench marks with GNSS will help to identify regions of the country where the GNSS-derived orthometric heights obtained using the 2022 Vertical Reference Datum will be more accurate than the current NAVD 88 leveling-derived orthometric heights.
My last column used the GPS on BMs dataset to identify potential issues in the published NAVD 88 heights. Figure 5, below, shows two stations (FA1337 and FA1560) are about 20 kilometers apart, and the difference in residuals is -18.6 centimeters (-12.4 centimeters minus 6.2 centimeters). This is a large difference for only 20 kilometers. What is even more significant is that the group of stations near FA1337 are all negative residuals (around -10 centimeters) and the group of stations near FA1560 are all positive residuals (around 6 centimeters). When the two stations are only 13 kilometers apart the GPS on BMs residual is 13.6 centimeters (Figure 6). These are two examples where the 2022 Vertical Reference Datum will provide a more accurate orthometric height difference between stations less than 20 kilometers apart. These differences are significant and could easily effect the results of many construction, transportation and flood plain mapping projects.
[FIGURE 5] Large GPS on BMS Residuals Between Stations 20 km Apart at the NC/SC Border (Note: rejections by geoid team have been removed)[FIGURE 6] Large GPS on BMS Residuals Between Stations 13 kilometers Apart in South CarolinaIn this column, we highlighted NGS plans for the 2022 Vertical Reference Datum and provided approximate height differences that users can expect to see. We also provided a little history behind the differences between the NGVD 29 and NAVD 88, and how each replacement of the vertical reference datum is improving the user’s ability to obtain the most accurate orthometric height.
![[FIGURE 2]](https://stage.globalpositioningnews.com/wp-content/uploads/2016/12/Fig2-NAVD-88-NGVD-29-Datum-Shift-Contours.jpg)
![[FIGURE 3] Coast-to-Coast Height Differences in the National Geodetic Vertical Datum of 1929 General Adjustment – Plot A](https://stage.globalpositioningnews.com/wp-content/uploads/2016/12/fig3-NGVD-29-genera-adjustment.jpg)
![[FIGURE 4] Coast-to-Coast Height Differences in the National Geodetic Vertical Datum of 1929 General Adjustment – Plot B](https://stage.globalpositioningnews.com/wp-content/uploads/2016/12/fig4-NGVD-29-general-adjustment.jpg)
![[FIGURE 5] Large GPS on BMS Residuals Between Stations 20 km Apart at the NC/SC Border (Note: rejections by geoid team have been removed)](https://stage.globalpositioningnews.com/wp-content/uploads/2016/12/Fig5-GPS-BMs-20km-NC-SC.jpg)
![[FIGURE 6] Large GPS on BMS Residuals Between Stations 13 kilometers Apart in South Carolina](https://stage.globalpositioningnews.com/wp-content/uploads/2016/12/Fig6-GPS-BMs-13km-NC-SC.jpg)