A new version 2.12 of the BKG NTRIP Client (BNC) will be available on April 18.
Originally developed in cooperation of the Federal Agency for Cartography and Geodesy (BKG) and the Czech Technical University (CTU) with a focus on multi-stream real-time access to GNSS observations, the software has been substantially extended.
The BKG Ntrip Client is an open source multi-stream client program designed for a variety of real-time GNSS applications. It was primarily designed for receiving data streams from any NTRIP supporting broadcaster. The program handles the HTTP communication and transfers received GNSS data to a serial or IP port feeding networking software or a DGPS/RTK application. In previous years, BNC has been enriched with RINEX quality and editing functions.
BNC on a Mac system for static real-time precise point positioning with Google Maps, such as for early warning of natural hazards.
Its primary objective is the promotion of open standards as recommended by the Radio Technical Commission for Maritime Services (RTCM). Implemented RTCM messages comprise satellite orbit and clock corrections, code and phase observation biases, and the Vertical Total Electron Content (VTEC) of the ionosphere.
Beside its graphical user interface, the real-time software for Windows, Linux and Mac platforms now comes with complete command line interface and considerable post-processing functionality. RINEX Version 3 file editing and quality check with full support of Galileo, BeiDou and SBAS — besides GPS and GLONASS — are among the new features.
Comparison of satellite orbit/clock files in SP3 format is another new feature of BNC.
BNC version 2.12 now allows a simultaneous multi-station Precise Point Positioning (PPP) for real-time displacement-monitoring of entire reference station networks.
BNC version 2.12 generates RINEX version 3.03 observation and navigation files to support near real-time GNSS post processing applications. Whenever BNC starts to generate RINEX observation files, it first tries to retrieve information needed for RINEX headers from so-called public RINEX skeleton files (skl files), which are derived from site logs. Therefore, BKG provides the current system observation types (sot files) per station. From April 18 onward, the sot files with BDS frequency bands consistent to the definition in RINEX version 3.03 will be provided.
Old configuration files cannot be used without problems. Nevertheless, BNC 2.12 download is coming out with a large set of examples for all the different applications, which can be easily adapted introducing a valid user account.
Basic procedures and tools for ensuring GNSS-derived orthometric heights meet the project’s desired accuracy
To date, this series of columns has addressed the following topics: basic concepts of GNSS-derived heights, National Geodetic Survey’s (NGS) guidelines for establishing GNSS-derived ellipsoid heights (NGS 58), differences between hybrid and scientific geoid models, procedures and tools for detecting GNSS-derived ellipsoid height data outliers, and basic procedures for estimating GNSS-derived orthometric heights (NGS 59). These columns are meant to provide the reader with basic concepts, routines, and procedures for analyzing, evaluating, and estimating GNSS-derived heights.
As mentioned in the last column “Determining valid North American Vertical Datum of 1988 (NAVD 88) published heights is the most important process when using GNSS data and geoid models to estimate GNSS-derived orthometric heights.” In Part 5 (February 2016) of this series, we discussed NGS 59 guidelines and methods for evaluating the results of the GNSS project. It provided methods for evaluating the results of the project and identifying stations with valid NAVD 88 published heights. In this column, we will continue to analyze the changes in adjusted heights due to different height constraints and compare the results to the published NAVD 88 orthometric heights.
First, we need to discuss what should be considered an outlier when identifying valid NAVD 88 published heights to be used as constraints. According to NGS guidelines for performing GNSS adjustments, the rule of thumb for outliers are shifts greater than 2 cm horizontally and 4 cm vertically (see highlighted section in the box below). The guidelines also stated that “It is important to realize that this threshold is merely a ‘rule of thumb.’ For individual projects, unconstraining a station may be necessary if shifts are less than the ‘rule of thumb’ threshold, and in some cases it can remain constrained even if shifts slightly exceed the threshold.”
It is important to understand this concept because constraining the height of a station influences the heights of stations nearby that constraint. Also, not constraining a published height of a station will result in establishing a new height for that station which means it could be inconsistent with other published stations nearby that station. If the station had moved since the last time it was leveled to then not constraining the height is the appropriate action to take. However, if the shift is due to some other reason (such as a previous adjustment distribution correction, or ellipsoid and/or geoid issue), then constraining the height may be the appropriate action to take. Selecting constraints is not an exact science; as a matter of fact, at times, it appears to be more like an art or like solving an enigmatic puzzle.
Excerpt of NGS Adjustment Document, adjustment_guidelines.pdf, under section 5 titled Constrained Horizonal Adjustment.
As a general rule, if the adjusted values of the constrained coordinates of a station shift by more than 2 cm horizontally and/or 4 cm in height, its horizontal coordinates and/or ellipsoid height, respectively, should be unconstrained. Doing so means that the published values for the unconstrained passive control station will be updated by the adjusted values determined in the submitted survey (CORS coordinates will not be updated). This 2 cm horizontal and 4 cm vertical threshold is consistent with that used by NGS for updating published CORS coordinates, although for CORS this is done by NGS independent of individual campaign-style GPS projects. It is important to realize that this threshold is merely a “rule of thumb.” For individual projects, unconstraining a station may be necessary if shifts are less than the “rule of thumb” threshold, and in some cases it can remain constrained even if shifts slightly exceed the threshold. The decision to constrain or not constrain also depends on other factors, such as the statistics of the adjustment, residuals, shifts at other stations, and station accuracies. It requires judgment and should not simply be an automatic response to constrained station shifts.
The NGS guideline mentioned above is for horizontal coordinates and ellipsoid heights. The NGS guidelines under section 6 implies that the user should apply the same guidelines for shifts between GNSS-derived orthometric heights and published NAVD 88 orthometric heights (see highlighted section in the box below). The guidelines also recommend that the user analyze the shifts of stations near each other to determine if stations nearby each other are shifting consistently or if one of the station’s value appears to be an outlier (see underlined section in box below).
Excerpt of NGS Adjustment Document, adjustment_guidelines.pdf, under section 6 titled Vertical Adjustment (Free and Constrained).
SECTION 6, VERTICAL ADJUSTMENTS (FREE AND CONSTRAINED)
6-1. Create the vertical free Afile (Afilevf). Fix one position and one published orthometric height. They can be from the same station or different stations (e.g., good horizontal position in one CC record for a CORS, good OH in separate CC record for a bench mark). Leaving column 77 of the CC record blank indicates the record contains an orthometric height value. Standard deviations of the constrained coordinates and heights should NOT be entered (i.e., columns 15-32 of the CC record should be blank).
Include the VS record from the horizontal constrained Afile.
70-76 Height, units of millimeters (integer)
77-77 Height Code blank — orthometric height
6-2. Run Adjust with minimum constraints. Input: Bfileght, Afilevf, Gfile, Output: adjvf.out, Bfilevf
Assuming the adjustment ran to completion, the statistics of this run will be identical to those of the horizontal free adjustment. Check adjvf.out for big shifts between published and free-adjusted heights.
It would be helpful to compute the shifts between the results of the vertical free adjusted and the published heights. Additionally, plot these shifts on a project sketch to determine if several heights near each other are shifting consistently or a height appears to be an outlier and therefore should not be used as control. For inconsistent shifts use resources available such as recovery notes, photographs, and rubbings of the mark. Possible causes could include movement, an unintended mark was observed such as the underground mark instead of the surface mark, or occupying a reference mark rather than the parent station. Look for inconsistent shifts as opposed to areas where the shifts, even high shifts, are consistent. Likewise, look at the geoid heights to ensure they are consistent. If no cause for the shift can be found, the orthometric height may need to be readjusted.
6-3. Create the vertical constrained Afile (Afilevc). Constrain all previously adjusted orthometric heights as indicated above and one NAD 83 adjusted position. The same comments about CC records apply. All GPS-derived Ht Mod heights should be constrained along with bench marks. For ht mod stations the datasheet will read:
HT_MOD – This is a Height Modernization Survey Station.
Include the VS record with its appropriate values.
6- 4. Run Adjust with vertical constraints. Input: Bfilevf, Afilevc, Gfile, Output: adjvc.out, Bfilevc
Run PrePlt2 to list and sort the residuals. Investigate observations with large shifts or residuals to see if any heights should be readjusted. Apply the same rule as in the horizontal constrained adjustment: no rejections due to constraints. Free any heights in question and rerun as a test. Note the differences between the published and readjusted heights obtained from the vertical constrained adjustment. Consider the requirements of the project before deciding whether to readjust additional points. Save the output Bfile from the final constrained vertical adjustment.
In Part 5, I highlighted a potential issue at station Phaniel. I’ve included the diagrams and tables from Part 5 that depicts the differences between GNSS-derived orthometric heights from a minimum-constraint adjusyment (using GEOID12B and xGeoid15b) and the published NAVD 88 height values (see figures 1-4, and tables 1-2). Looking at figures 1 and 2, there are several large differences between closely spaced constraints when using the hybrid geoid model – Phaniel, Buffalos 2, V 49, and Row 9. As stated in Part 2, the user should compute the results using both the hybrid and the scientific geoid models. Figures 3 and 4 depict the differences using the scientific geoid model xGeoid15b. Notice that the large differences between Phaniel and Buffalo 2 decreased from 4.9 cm using GEOID12B to 0.7 cm using xGeoid15b. However, the larger relative difference between Phaniel and V 49 (3.8 cm) and ROW 9 (5.2 cm) still exists. Also, the difference between Buffalo 2 and V 49 is large (3.1 cm), and Buffalo 2 to Row 9 is large (4.5 cm), but the difference between V 49 and Row 9 is less than 2 cm. The neighbor stations of Row 9 all seem to agree within a couple of centimeters indicating that Buffalo 2 may be a station that needs further investigation.
Figure 1. [Figure 3 from Part 5] Diagram depicting differences between GNSS-derived orthometric heights from a Minimum-Constraint Adjustment (using GEOID12B) and published NAVD 88 height values (units=cm).Figure 2. [Figure 4 from Part 5] Diagram depicting differences between GNSS-derived orthometric heights from a Minimum-Constraint Adjustment (using GEOID12B) and published NAVD 88 height values (units=cm).
Figure 3. [Figure 5 from Part 5] Diagram depicting differences between GNSS-derived orthometric heights from a Minimum-Constraint Adjustment (using xGeoid15b) and published NAVD 88 height values (units=cm).Figure 4. [Figure 6 from Part 5] Diagram depicting differences between GNSS-derived orthometric heights from a Minimum-Constraint Adjustment (using xGeoid15b) and published NAVD 88 height values (units=cm).
Next we need to look at the adjusted ellipsoid heights from a minimum-constraint solution compared to the published ellipsoid heights. This procedure was decribed and demonstrated in Part 4. Figure 5 is plot of adjusted ellipsoid height minus published NAD 83 (2011) ellipsoid heights for stations near Phaniel. Figure 5 indicates that the adjusted ellipsoid heights at Buffalo 2, Phaniel, and V 49 all agree within 2 cm. As a matter of fact, Buffalo 2 and Phaniel agree to better than 1 cm from the NAD 83 (2011) published heights. This is an indication that the orthometric height of station Phaniel may be an outlier and should not be constrained. The leveling network in the area requires investigation to validate this conclusion. This will be addressed in a future column. Looking at Tables 1 and 2, two other stations, stations Plaza and Row 3, have large differences between the GNSS-derived orthometric heights from a minimum-constraint adjustment and the published NAVD 88 heights, and they should be investigated.
Figure 5. Plot of adjusted ellipsoid height minus published NAD 83 (2011) Ellipsoid Heights for Stations near Phaniel (the number is the difference for that particular station; units = cm).Table 1. Differences between GNSS-derived orthometric heights from a minimum-constraint adjustment (using GEOID12B) and published NAVD 88 heights (GEOID12B results sorted and highlighted).Table 2. Differences between GNSS-derived orthometric heights from a minimum-constraint adjustment (using xGeoid15b) and published NAVD 88 heights (xGeoid15b results sorted and highlighted).
Figure 6 is a diagram depicting differences between GNSS-derived orthometric heights from a minimum-constraint adjustment using GEOID12B and published NAVD 88 heights surrounding station Plaza. The user should notice that the relative difference in height changes between Plaza and 37 DRD is -3.8 cm (-2.5 – 1.3) and between Plaza and Fifth it is -3.2 cm (-2.5 – 0.7). This is an indication that there is a potential issue with station Plaza. Next, we need to compute the results using xGeoid15b. Figure 7 is a plot of the differences surrounding station Plaza using xGeoid15b. Figure 7 shows that station Plaza outliers relative to station 37 DRD and Fifth are exactly the same, i.e., -3.8 cm (-3.2 – 0.6) and -3.2 cm (-3.2 – 0.0) respectively. Something interesting to note is that station J 181 difference decreased from 2.1 cm using GEOID12B (see figure 6) to 1.1 cm using xGeoid15b (see figure 7). Once again, this is a reason why users should use both the hybrid geoid model and the scientific geoid model when analyzing GNSS-derived orthometric heights.
Figure 6. (More Detail at Station Plaza) Diagram depicting differences between GNSS-derived orthometric heights from a Minimum-Constraint Adjustment (using GEOID12B) and published NAVD 88 height values (units=cm).
Figure 7. (More Detail at Station Plaza) Diagram depicting differences between GNSS-derived orthometric heights from a Minimum-Constraint Adjustment (using xGeoid15b) and published NAVD 88 height values (units=cm).
The other station to investigate based on the large difference in table 2 is station Row 3. Figure 8 is a diagram depicting the differences near station Row 3 using GEOID12B. Notice that the difference at Row 3 is considerably less than the 4 cm; however, the relative difference between Row 3 (-2.7 cm) and station 384 JAS (0.2 cm) is -2.9 cm. This doesn’t seem too large but computing the results using xGeoid15b indicates something different. Figure 9 is a plot of the differences using the scientific geoid model xGeoid15b. Notice that the difference at station Row 3 increased to -3.8 cm and the relative difference between Row 3 and 384 JAS is -3.9 cm. Note, this again emphases the importance of using both the hybrid and scientific geoid models when analyzing GNSS-derived orthometric heights. This large relative difference is an indication that the height of station Row 3 may not have a valid NAVD 88 published height and should be further investigated before constraining the height in the final adjustment.
Figure 8. (More Detail at Station Row 3) Diagram depicting differences between GNSS-derived orthometric heights from a Minimum-Constraint Adjustment (using GEOID12B) and published NAVD 88 height values (units=cm).Figure 9. (More Detail at Station Row 3) Diagram depicting differences between GNSS-derived orthometric heights from a Minimum-Constraint Adjustment (using xGeoid15b) and published NAVD 88 height values (units=cm).
After analyzing the differences between GNSS-derived orthometric heights from a minimum-constraint adjustment and published NAVD 88 heights to help identify potential outliers, the user can perform a constrained adjustment holding the published height values as constraints. The user should ensure that a constraint does not significantly affect the adjusted heights of neighboring stations. To understand the effects of the constraints on the heights of stations that are not constrained, the user can plot the changes in adjusted heights between the constrained adjustment and the minimum-constraint adjusted heights (with a bias removed). As mentioned in Part 5, any constraint can be used to obtain a minimum-constraint solution so removing a bias based on the differences between the published height values and the adjusted height values obtained from a solution constraining one published height is appropriate. Figure 10 is a plot that depicts the differences between the adjusted heights from an adjustment with all published NAVD 88 height values constrained and the adjusted heights values from the minimum-constraint adjustment. Figure 10 highlights the large relative changes of closely spaced stations such as between Phaniel (-2.8 cm) and Open (-0.6 cm). This means that the constraint at station Phaniel has changed the relative height difference between station Phaniel and station Open by 2.2 cm. This is a large change when you trying to obtain 2 cm heights. Another method to see the effect of the constraints is by plotting the changes in “dU” residuals between the constrained adjustment and the minimum-constraint adjustment. Figure 11 is a plot of the differences in vector “dU” residuals between the constrained adjustment (with all published heights constrained) and the minimum-constraint adjustment.
Figure 10. Diagram depicting differences between GNSS-derived orthometric heights from a Constrained Adjustment (All Published Heights Constrained) minus Minimum-Constraint Adjustment (using GEOID12B) – units=cm.
Looking at figure 11, the user can quickly see that constraining station Phaniel has changed the three vectors associated with Phaniel by 1.9 cm, 2.1 cm, and 2.3 cm. This means that the observed vectors were changed by 2 cm to be consistent with the constraint at Phaniel. This could have an impact on a surveyor performing leveling between these two stations. The analyst should now perform an adjustment not constraining the stations identified as potential outliers. At this moment, in this study, stations Phaniel, Plaza, and Row 3 are considered questionable and their heights will not be constrained.
Figure 11. Diagram depicting differences between dU Residuals of Vectors from a Constrained Adjustment (All Published Heights Constrained) minus Minimum-Constraint Adjustment (using GEOID12B) – units=cm.
Figure 12 is a diagram depicting the differences between the GNSS-derived orthometric heights from a constrained adjustment were the height values of stations Phaniel, Plaza, and Row 3 were not constrained. Figure 13 is a diagram depicting the differences between the dU residuals of baselines from the constrained adjustment with heights of stations Phaniel, Plaza, and Row 3 not constrained and the dU residuals from the minimum-constraint adjustment. Figures 14 and 15 provide more detail of the changes in residuals near station Phaniel. Figure 14 depicts the differences when all NAVD 88 heights are constrained and figure 15 depicts the differences when the suspected stations (Phaniel, Plaza, and Row 3) are not constrained. Comparing figures 14 and 15 clearly show that by constraining station Phaniel, the relative differences between station Phaniel and its neighbors are adversely effected by the constraint. For example, the difference in dU residuals between Phaniel and Brown Az Mk decreased from 2.3 cm to -0.2 cm resulting in a 2.5 cm relative height change.
Figure 12. Diagram depicting differences between GNSS-derived orthometric heights from a Constrained Adjustment (Three Stations Unconstrained) minus Minimum-Constraint Adjustment (using GEOID12B) – units=cm.Figure 13. Diagram depicting differences between dU Residuals of Vectors from a Constrained Adjustment (Three Stations Unconstrained) minus Minimum-Constraint Adjustment (using GEOID12B) – units=cm.Figure 14. (More Detail at Station Phaniel) Diagram depicting differences between dU Residuals of Vectors from a Constrained Adjustment (All Stations Constrained) minus Minimum-Constraint Adjustment (using GEOID12B) – units=cm.Figure 15. (More Detail at Station Phaniel) Diagram depicting differences between dU Residuals of Vectors from a Constrained Adjustment (Three Stations Unconstrained) minus Minimum-Constraint Adjustment (using GEOID12B) – units=cm.
As previously mentioned, station Plaza is another station with a large difference between the adjusted height from the minimum-constraint adjustment and its published height (see tables 1 and 2). Constraining station Plaza results in very large dU residuals between station Plaza and station 37 DRD, i.e, 3.7 cm over a distance of 1.1 km (see figure 16). By not constraining the height of station Plaza the dU residuals on the vector between station Plaza and station 37 DRD changed from 3.7 cm to 0.4 cm (see figure 17). Also, the dU residuals on the vector between station College and station Hudson changed from -1.8 cm to -0.1 cm, and dU residuals on the vector between station Dorsett and station Hudson changed from -1.7 cm to 0.2 cm. The distance between Dorsett and Hudson is 1.2 km. The allowable section closure for second-order, class 2 leveling in 1.2 km is 0.88 cm. If a user wanted to check their leveling work using these two stations they may not check within the allowable because of the large distribution correction applied to the adjusted heights due to constraining the height of station Plaza.
Figure 16. (More Detail at Station Plaza) Diagram depicting differences between dU Residuals of Vectors from a Constrained Adjustment (All Stations Constrained) minus Minimum-Constraint Adjustment (using GEOID12B) – units=cm.Figure 17. (More Detail at Station Plaza) Diagram depicting differences between dU Residuals of Vectors from a Constrained Adjustment (Three Stations Unconstrained) minus Minimum-Constraint Adjustment (using GEOID12B) – units=cm.
Next, the user should look at the differences in ellipsoid heights between minimum-constraint adjustment and published NAD 83 (2011) ellipsoid heights in the area of station Plaza (see figure 18). Station Plaza did not have a published NAD 83 (2011) ellipsoid height but the closest two stations (Dorsett and Salisbury CORS ARP) both agree within 0.6 cm of the published NAD 83 (2011) ellipsoid heights. This is a good sign tht the ellipsoid heights meet the desired accuracy but doesn’t help to explain the large difference at station Plaza.
Figure 18. (More Detail at Station Plaza) Diagram depicting differences between Adjusted GNSS-Derived Ellipsoid Heights (with average bias removed) minus Published NAD 83 (2011) Ellipsoid Heights (units=cm).
The third station with a large relative difference highlighted in table 2 is station Row 3. Figures 19 and 20 provide more detail of the changes in residuals near station Row 3. Notice that the dU residual of the vector between station Railroad and Magna changed from 1.5 cm to 0.1 cm when the height of Row 3 is not constrained. The distance between the two stations is 4 km so the effect of constraining this station is not really significant. It should be noted that one of the reasons it’s being investigated is because of the large relative difference between Row 3 and station 384 JAS using xGeoid15b (-3.9 cm, see figure 9). Figure 21 is a plot of the differences in ellipsoid heights obtained from the minimum-constraint adjustment and their published NAD 83 (2011) ellipsoid heights in the vicinity of station Row 3. Station Row 3 does not have a published NAD 83 (2011) ellipsoid height but all of the stations surrounding the station are less than 2 cm. There does not appear to be any large outliers compared with the published ellipsoid heights in the area. Once again, this means that the next step in the process is to investigate the leveling network in the area.
Figure 19. (More Detail at Station Row 3) Diagram depicting differences between dU Residuals of Vectors from a Constrained Adjustment (All Stations Constrained) minus Minimum-Constraint Adjustment (using GEOID12B) – units=cm.Figure 20. More Detail at Station Row 3) Diagram depicting differences between dU Residuals of Vectors from a Constrained Adjustment (Three Stations Unconstrained) minus Minimum-Constraint Adjustment (using GEOID12B) – units=cm.Figure 21. (More Detail at Station Row 3) Diagram depicting differences between Adjusted GNSS-Derived Ellipsoid Heights (with average bias removed) minus Published NAD 83 (2011) Ellipsoid Heights (units=cm).
Up to this point we have analyzed changes in adjusted heights due to different constraints and compared the results to the published NAVD 88 GNSS-derived orthometric heights to identity stations that should be constrained in the final adjustment. As one can see, performing GNSS-derived orthometric height adjustments is more like an art than an exact science. There are a lot of variables and unknowns. Every constraint has an influence on the final set of adjusted heights. Determining this effect and the consequences of selecting an invalid constraint has been described in this column.
When incorporating new geodetic data into the National Spatial Reference System, it is important to maintain consistency between neighboring stations. If the published height of a station is not constrained, it will be superseded by the newly adjusted height. If the station has moved since the last time its height was established then superseding the height is the appropriate action to take. If the difference is due to some other reason such as the results of a previous adjustment distribution correction then superseding the height may not be the appropriate action to take.
In my next column, Part 7, we will look at the design of the NAVD 88 leveling network and published heights in the area to help determine the final set of stations to constrain.
Leica Geosystems released its new generation of reference servers and monitoring receiver, optimized with multi-frequency 555-channel capabilities to connect with current and all anticipated GNSS signals.
The Leica Geosystems GM30 receiver.
The new Leica GR30 and GR50 reference servers and GM30 monitoring receiver are primed for the constantly changing requirements of GNSS technology, according to the company. The first equipped with 555 channels, the new reference stations and monitoring receivers support all global GNSS constellations, such as GPS, GLONASS, Galileo and BeiDou, as well as regional systems such as QZSS and SBAS.
The receivers seamlessly work with a multitude of signals so that monitoring professionals, geodetic research and engineering specialists can obtain high-quality data and continuous, uninterrupted accuracy.
These new reference servers and monitoring receiver are part of Leica Geosystems’ GNSS streamlined solution — with standard open interfaces, they can be seamlessly integrated with other existing systems. According to Leica, maximum benefit with minimum effort is achieved through automated firmware updates, plug-and-play connectivity, simultaneous and multiple communications interfaces, power supply and logging capabilities.
“When considering a GNSS reference station solution, superior quality and long product life is very important,” said Frank Pache, senior product manager of Leica Geosystems. “Our new reference servers fulfil this demand. In addition, users who have already invested in the previous generation Leica GR10 and GR25 Unlimited solutions can now benefit from the free upgrade to the new Leica GR30 and GR50 reference servers. They can enjoy the peace of mind that comes with being equipped with today’s and tomorrow’s GNSS signals.”
Thanks to the comprehensive and user-friendly web interface, both GNSS network beginners and highly experienced professionals have complete and easy control. Leica Active Assist’s support team make sure your GNSS projects run smoothly by providing live and secure onboard assistance whenever needed.
Scientists, researchers and engineers are also provided with detailed information about movements of man-made and natural structures as well as real-time position solutions. Three different modes, specifically designed to work with reference station, structural and network real-time kinematic (RTK) service monitoring continuously provide specialists with real-time precision data.
The Leica GM30 monitoring receiver is also part of the GeoMoS solution, delivering timely and actionable information to respond quickly and minimize dangerous and costly damages.
The reference servers and receiver are also part of the Leica Spider family, a suite of software providing RTK services for tailor-made solutions.
SkyTraq Technology Inc., developer of high-performance chipset and module solutions for the GNSS market, unveiled its new S2525F8-RTK low-power, single frequency RTK receiver for applications requiring centimeter-level accuracy positioning.
S2525F8-RTK is a multi-constellation GNSS RTK receiver that can use 12 GPS, eight SBAS, six BDS, and one QZSS signal. In situations where an RTK fix is not possible, a Float RTK mode can be used for decimeter-level accuracy positioning.
A moving-base mode supports a precise heading GPS compass application. The receiver is 25 millimeters by 25 millimeters form factor, weighs 3 grams and consumes 250 milliwatts of power for any outdoor mobile applications requiring high precision RTK positioning, SkyTraq reported in a news release.
S2525F8-RTK supports both base station and rover modes. As a rover, it receives RTCM (Radio Technical Commission for Maritime Services) 3.0 or 3.1 data from a base station — or raw measurements from another S2525F8-RTK receiver serving as base station — and performs carrier phase RTK processing to achieve relative positioning with 1 centimeter plus 1 part-per-million position accuracy with 10-kilometer baseline. Decimeter-level accuracy for over 10-kilometer baseline can be achieved using the Float RTK mode. Two S2525F8-RTK receivers can be used to form a GPS compass that provides better accuracy and more reliable heading solution than conventional digital magnetometers that’s affected by changes in the magnetic environment, according to SkyTraq.
A $50 NS-HP evaluation board is available for evaluation and integration into portable survey equipment, unmanned vehicles, machine control applications and robotic guidance applications. The standard NMEA-navsat-driver package of Robot Operating System (ROS) works directly with NS-HP, enabling accessible centimeter-level accuracy positioning for robotic applications, SkyTraq says.
A GPS World webinar on April 14 explores how five organizations made the switch to using their own tablets and smartphones for field data collection (also known as bring your own device, or BYOD).
Lance Fugate of Enmapp based in Calgary inspects pipelines using TerraGo Edge on iPads.
Webinar participants will learn about and benefit from the real-world challenges faced during the five deployments of BYOD GPS field data-collection solutions. These customers and projects span very different industries, working conditions and requirements for GPS field data collection. Each offers a unique perspective based on their requirements and ultimately their approach to using smartphones and tablets for GPS-powered asset inspections, surveys, field service and remote workforce management.
The City of Sebring Water Utility faced challenges with field crew use of CAD diagrams, as well as obtaining RTK accuracy on iPads. Read more about the Sebring project in this article from our March issue.
The State of Louisiana needed to complete more than 4,000 miles of annual levee inspections while syncing field data from tablets to the cloud. Read more about the project.
Kleinfelder engineers needed to shift to real-time GPS on tablets so they could eliminate four hours per day of post-field processing, and bring projects in faster and under budget.
Empire Electric needed a method for customers to approve GPS-tagged work orders in real-time from the job site to avoid delays and lower costs.
Enmapp needed to cut pipeline inspection hardware and labor costs in the face of the oil industry’s low-price and margin-challenged cost environment.
The American Association for Geodetic Surveying (AAGS) has undertaken an effort to explore creating a geodetic certification program. The geodetic certification would provide official recognition that a person has the working knowledge and skills to understand and solve practical problems in applied geodesy.
The vision is that the geodetic certification program would be similar to other existing certifications, such as the American Society for Photogrammetry and Remote Sensing (ASPRS) Certified Photogrammetrist, the GIS Certification Institute (GISCI) GIS Professional, and the National Society of Professional Surveyors (NSPS) and The Hydrographic Society of America (THSOA) Certified Hydrographer.
“As geospatial technology continues to advance and gain wider adoption, geodesy is becoming an increasingly important part of the geospatial framework,” said AAGS past president Michael Dennis, RLS, PE. “To that end, we are exploring the concept of creating a program that officially recognizes professionals with a minimum level of geodetic competence.”
To gain input from industry professionals, AAGS created an online questionnaire about the program and invites all those involved with geospatial technologies to contribute. The questionnaire is available here.
The questionnaire is intended to serve multiple purposes:
Establish an appropriate body of knowledge for applied geodesy
Determine the level of support in the geospatial community
Identify areas of interest and existing status of geodetic knowledge
Provide guidance on creating and prioritizing educational content
Show the breadth and depth of the field of geodesy
Raise awareness of the proposed program
The questionnaire also helps lay the foundation for creating a certification program and consists of 50 questions. The first ten are general questions, and the remaining 40 are divided among the eight topic areas listed below.
Geometrical Geodesy and Reference Systems
Map Projections
Physical Geodesy
Astronomic and Celestial Coordinate Systems
Global Navigation Satellite Systems
Statistics and Least Squares
Geodetic Observation Procedures and Practices
Standards, Specifications, and Guidelines
AAGS is seeking input from a broad cross section of geospatial practitioners, including surveyors, engineers, GIS professionals, photogrammetrists, programmers and any others who use geodetic methods and calculations to combine, manipulate, and analyze spatial data.
The proposed geodetic certification program is being developed in cooperation with the National Society of Professional Surveyors (NSPS). Participation of other professional geospatial organizations is currently being solicited as part of program development.
Hemisphere GNSS has released the S321, its next-generation multi-frequency, multi-GNSS survey smart antenna. The S321 — designed for land or marine survey — combines Hemisphere’s Athena and Atlas technologies with a new web user interface offering customer-friendly performance.
For professional marine applications — such as marine construction, hydrographic surveying or dredging — using the S321 with Athena RTK (real-time kinematic) enables users to achieve impeccable results and maintain peak up-time, the company said. The ruggedized antenna was designed for demanding and challenging environments and meets IP67 requirements.
The S321 smart antenna by Hemisphere GNSS.
“The S321 is another example of how much Hemisphere has changed,” said Chuck Joseph, president and CEO. “A fantastic survey smart antenna with industry-leading RTK, connectivity, and management capabilities, the S321 offers unbeatable performance and value to the industry.”
Athena RTK
Athena excels in environments where high-accuracy GNSS receivers can be used. Hemisphere’s customers have tested and proven Athena’s performance in long baseline, in open-sky environments, under heavy canopy, and in locations experiencing significant scintillation.
Initialization time – Reliably consistent initialization performance, while at the same time performing initializations in less than 15 seconds at better than 99.9 percent reliability.
Robustness in difficult operating environments – Extremely high productivity under aggressive geographic and landscape-oriented environments for GNSS.
Performance on long baselines – Position stability for long baseline applications.
Performance under scintillation – Sustained accuracy under ionospheric scintillation activities.
Atlas GNSS Global Corrections
The S321 ships preconfigured to test drive corrections from Hemisphere’s Atlas global corrections service. The bundled solution provides users worldwide with an easy way to use Atlas, including the worldwide H10 service offering 8-centimeter, 95-percent accuracy (4 cm RMS).
Network RTK Augmentation
BaseLink technology allows Atlas-capable receivers like the S321 to self-calibrate, self-survey, and automatically manage the transmission of RTK correction data to augment or extend established or new GNSS reference networks in areas of poor Internet connectivity.
The S321 introduces Hemisphere’s aRTK technology. Powered by Atlas, aRTK enables the S321 to operate with RTK accuracies when RTK corrections fail. If the S321 is Atlas-subscribed, it will continue to operate at the subscribed service level until RTK is restored.
The S321 also introduces SureFix, Hemisphere’s new processor running in combination with Athena to provide high-fidelity RTK quality information that results in guaranteed precision with virtually 100 percent reliability.
Features:
Athena RTK engine
GPS, GLONASS, BeiDou, Galileo, QZSS
372 channels
Atlas corrections delivered via L-band and over the Internet
Wireless connectivity via Bluetooth and Wi-Fi
Powerful web user interface
Two versions (Each can be configured as Base or Rover):
UHF + GSM / WCDMA
GSM / WCDMA (Network Rover)
4 GB internal memory card and 64 GB-capable MicroSD card for data logging, download and upload.
The S321 can be ordered now and is available to ship before the end of the month.
The S321 is making its tradeshow debut at Oceanology International 2016 at ExCeL, London, UK, March 15-17, at booth G500.
For more information about the S321, Athena, Atlas, or its other advanced features, please call +1 (844) 217-2845 (within Canada / USA only) or +1 (480) 291-6766, or email [email protected].
By Martti Kirkko-Jaakkola, Stefan Söderholm, Salomon Honkala, Hannu Koivula, Sonja Nyberg, and Heidi Kuusniemi, Finnish Geospatial Research Institute (FGI), National Land Survey of Finland
Our real-time kinematic (RTK) implementation, the Public Precise Positioning (P3-Service) project, has achieved horizontal positioning accuracy of 0.5 meters using relatively inexpensive equipment: a commercial off-the-shelf (COTS) low-cost GNSS receiver. The project used FinnRef, the Finnish national GNSS network.
With inter-station baselines on the order of 200 kilometers, FinnRef is relatively sparse in comparison with commercial RTK networks. We used FinnRef as the RTK base station, either in single-base or network RTK mode. Although FinnRef’s main purpose is to maintain the national coordinate system, it is also capable of delivering DGNSS and network RTK data over the NTRIP protocol.
Transport Applications. Horizontal position accuracy of 0.5 meters or better, achieved for more than 90 percent of the time with small, low-cost devices, could be useful in various applications, particularly in intelligent transportation systems.
Current consumer-grade GNSS solutions routinely offer a positioning accuracy in the order of 5 meters, and satellite-based augmentation systems (SBAS) such as WAAS and EGNOS can improve the accuracy to the order of 1 meter. However, this is not adequate for all use cases; in particular, intelligent transportation systems (ITS) require better positioning performance. For instance, a horizontal accuracy of 0.5 meters is needed to reliably identify the lane in which a vehicle is driving. Maintaining inventory of machines, road signs and other infrastructure would also benefit from sub-meter accuracy.
Sub-meter or even sub-decimeter positioning accuracies can be attained with a relatively good reliability in real time if a dual-frequency GNSS receiver and a physical or virtual base station are available. However, such receivers and virtual base station services are currently too expensive to gain popularity in the mass market. Recently, precise point positioning (PPP) has demonstrated that comparable accuracies can be attained without a base station using real-time precise correction data, but its drawback is a long convergence time. In contrast, differential methods utilizing raw base-station observations, such as RTK, converge much faster.
Horizontal position estimation results from a low-cost COTS receiver (right); the green triangle marks the reference position solution.
Network RTK Test. Network RTK performance was tested in a static scenario with the closest physical base station 63 kilometers from the rover receiver. Network corrections were delivered in the PRS representation, and data were logged for 20 minutes at a rate of 1 Hz. The plot above shows the resulting horizontal position errors. The dashed red circle with a radius of 0.5 meters centered at the reference location (green triangle) contains 90.4 percent of the position estimates.
For a full account of the experiments and results described here, see the paper “Low-Cost Precise Posioning Using a National GNSS Network,” presented at ION GNSS+ 2015.
Anatum Field Solutions (AFS) has launched a nationwide BYOD (Bring Your Own Device) submeter GNSS and centimeter (RTK) GNSS receiver rental program. With the explosion of smartphones and tablets in recent years and the availability of universal Bluetooth submeter and real-time kinematic (RTK) GNSS receivers, high-accuracy GNSS data collection is available to everyone.
AFS rentals target high-accuracy users in GIS, UAV, environmental, engineering, surveying, agriculture, electric/gas/water utilities, pipeline, forestry, mining, transportation, construction, architecture, and federal/state/local government markets.
AFS offers all mobile GIS devices including Apple iOS, Android, Windows and Windows Mobile/EHH. It also stocks various GNSS receivers such as Eos Arrow (submeter and centimeter), SXBlue (submeter and centimeter), Trimble R1 (1 meter) and BadElf (1-3 meters) in a variety of configurations.
“We intend to make centimeter and submeter accuracy GNSS receivers available to everyone, even if you only need it for a couple of days,” said Matt Alexander, Vice President at AFS. “Our full rental systems come complete with GNSS receiver, tablet with cellular data, data collection software and accessories. You can literally be collecting centimeter-accurate data within minutes of opening the box, no matter what your experience level is.”
AFS can accommodate a wide variety of mobile GIS software solutions with its systems, including Esri’s ArcGIS Collector, Survey123 and ArcPad; iCMTGIS; TerraGo; AmigoCloud; Avenza PDF Maps; Fulcrum; and tMap. AFS provides the software tools and technical support to turn mobile GIS software into centimeter or submeter-accurate data-collection systems.
AFS offers three different rental configurations:
Complete systems including GNSS receiver, tablet computer with cellular data plan, mobile GIS software and accessories. Ready to map.
GNSS receiver and tablet computer with cellular data plan (user logs into their own mobile GIS account).
GNSS receiver (centimeter or submeter) only. Ready to connect to your mobile device.
All rentals come with a return shipping label so the user can leave the box at a FedEx pick-up location, hotel counter, office counter or anywhere that Fedex picks up.
Topcon Positioning Group announces the release of a new full wave geodetic antenna — the G5-A1. The portable antenna is designed to provide improved multipath mitigation for use with a mobile base station site or network reference station.
“When paired with the Topcon NET-G5 receiver, the zero-centered geodetic antenna provides a powerful and cost-effective entry-level solution” said Charles Rihner, vice president of the Topcon GeoPositioning Solutions Group.
The G5-A1 is optimized for geospatial industries and designed to track all globally available and developing satellite constellations. The antenna weighs approximately 1 pound (.5 kg) and is 7 inches (17.9 cm) wide.
“With its portability and geodetic level performance, the new G5-A1 antenna provides an excellent choice for mobile base system and economy reference station system,” Rihner said.
The Louisiana Department of Transportation and Development (DOTD) has deployed TerraGo Edge for the inspection of flood protection infrastructure including levees, dams and reservoirs.
The DOTD’s Public Works and Water Resources Division inspects more than 1,100 miles of levees, four times every year.
The legacy inspection system was a custom-built application developed by an engineering services firm, which used Trimble Yuma ruggedized tablets. Over time, the system became less reliable and database updates were cumbersome and problematic. To truly fix the system would have meant more custom development services and other expenses.
Each of the six Yuma tablets, fully configured, ran around $6,000. The annual software maintenance was also expensive at around $18,000, which did nothing to improve the reliability of the system.
“We really wanted a cloud-based system, so we wouldn’t need to maintain a database server on-site. And if we could deploy an Android solution, those tablets would only cost us about $200, so the hardware would be pennies on the dollar. We could break and replace a lot of Android tablets compared to a traditional, ruggedized GPS tablet at $6,000,” said Doug Taylor, Director of Levees, Dams and Reservoirs at the DOTD.
After a series of successful field trials, DOTD knew it had found a mobile solution that met their requirements across the board for reliability, ease of use and customizability, all with a cloud-based database solution at a fraction of the cost.
TerraGo Edge’s customizable forms mean the DOTD never has to pay a software services fee for modifying a hard-coded solution again. They can design their own forms, maps and workflows, flexibly changing them whenever needed to improve the speed and quality of inspections and maintenance.
“Honestly, my favorite part about TerraGo Edge is that it’s just easy to use,” said Taylor. “It’s easy to use in the field and it’s easy to get information and reports out whenever we need them. The challenge is always how to figure out the right forms and inspection workflow. We have hundreds of codes and things change over time. With Edge, we can customize our forms and process today, and know we can adjust things in the future. ”
SBG Systems has released the Apogee-M and the Apogee-U, two inertial sensors, to complete the Apogee product line.
The Apogee-M is a motion reference unit (MRU), and the Apogee-U is an inertial navigation system (INS). Both are made of titanium with a depth rating of 200 meters.
Apogee Series is an accurate INS based on robust micro-electro-mechanical systems (MEMS) technology. One year after the successful release of Apogee surface sensors (IP68 enclosure), SBG Systems completes the product line with the two inertial sensors, which have titanium subsea enclosures (200-meter depth rating).
Accuracy. Apogee integrates the latest generation of MEMS sensors to reach a high degree of precision — 0.008 degrees in roll and pitch in real-time — while delivering a robust and accurate heading from the continuous fusion of GNSS and IMU data. Made of titanium, Apogee-M and Apogee-U are designed to mount close to the sonar head for hydrographic tasks from shallow to deep water.
Heave computation. The Apogee provides a real-time heave accurate to 5 centimeters, which automatically detects the wave frequency and constantly adjusts to it. When wave frequency is erratic or in case of long period swell, the delayed heave feature can save the day by allowing survey in rough conditions. This algorithm allows a more extensive calculation, resulting in a heave accurate to 2 cm displayed in real-time with a short delay.
Connects to survey-grade GNSS receivers. Apogee sensors can be paired with any type of survey-grade GNSS receiver or with the one offered by SBG Systems. The SplitBox GNSS integrates the latest tri-frequency GNSS receiver to offer several positioning features such as RTK, Marinestar, OmniSTAR, Veripos and TerraStar corrections.
Configuration is acomplished throughout the intuitive, embedded web interface where all parameters can be quickly displayed and adjusted. The new 3D View helps the user check the mechanical installation, especially sensor and antennas position, alignments and lever arms. The user can then connect the Apogee to the main hydrographic software such as Hypack, QINSy or Teledyne PDS2000, thanks to available drivers.
The MEMS technology is renowned for being highly robust and low-maintenance, while the subsea enclosure is made in titanium. SBG SYSTEMS continuously make its systems evolve with new firmware upgrades that are available during the whole life of the product without extra cost.
![Figure 1. [Figure 3 from Part 5] - Diagram depicting differences between GNSS-derived orthometric heights from a Minimum-Constraint Adjustment (using GEOID12B) and published NAVD 88 height values (units=cm).](https://stage.globalpositioningnews.com/wp-content/uploads/2016/04/Rowan-County_Newsletter_5_3.jpg)
![Figure 2. [Figure 4 from Part 5] - Diagram depicting differences between GNSS-derived orthometric heights from a Minimum-Constraint Adjustment (using GEOID12B) and published NAVD 88 height values (units=cm).](https://stage.globalpositioningnews.com/wp-content/uploads/2016/04/Rowan-County_Newsletter_5_4.jpg)
![Figure 3. [Figure 5 from Part 5] - Diagram depicting differences between GNSS-derived orthometric heights from a Minimum-Constraint Adjustment (using xGeoid15b) and published NAVD 88 height values (units=cm).](https://stage.globalpositioningnews.com/wp-content/uploads/2016/04/Rowan-County_Newsletter_5_5.jpg)
![Figure 4. [Figure 6 from Part 5] - Diagram depicting differences between GNSS-derived orthometric heights from a Minimum-Constraint Adjustment (using xGeoid15b) and published NAVD 88 height values (units=cm).](https://stage.globalpositioningnews.com/wp-content/uploads/2016/04/Rowan-County_Newsletter_5_6.jpg)
