Trimble Business Center Matrix

[Carmine Osterland]

Recentlybeen having issues while working with this datum transformation. My company is working on a project where data comes from Trimble GPS receivers and also survey data. The survey data is both exported from Trimble Business center and also transformed with PostGIS using Proj4 into local state plane coordinates. The GPS data is post-processed with Trimble Pathfinder office and exported as shapefiles into the local state plane coordinate system. The shapefiles are then imported into our SDE which is in WGS84 using the WGS_1984_(ITRF00)_To_NAD_1983 Datum transformation.

When comparing data exported from PostGIS to the data in our SDE they line up fine in ArcMap, until I apply the WGS_1984_(ITRF00)_To_NAD_1983 Datum transformation to my map document (ArcMap 10.5). We see a 1m shift between the datasets when the datum transformation is applied.

It appears that there is no datum transformation applied to the survey data that is transformed using PostGIS/Proj4. Digging deeper I found that between WGS84 and NAD83 there is essentially no difference between the two- at least the original iteration of WGS84 and NAD83. Going even further, I confirmed in Pathfinder Office that there is no transformation between WGS84 and NAD83 (see attachment) . I noticed that the transformation values applied in ArcGIS using WGS84 using the WGS_1984_(ITRF00)_To_NAD_1983 match the transformation values exactly to what Trimble Pathfinder office uses for NAD 1983 (Conus) CORS96 (see attachments).

Thanks Joel, yes it does seem like that would be a good idea to do a compare. I always thought it was a black & white issue- where you apply the 'most accurate' datum transformation when migrating between coordinate systems. I've been applying datum transformations to my data for years and now I'm not sure if that's the correct thing to do. Especially when working with KMZ files from my clients- I guess it's impossible to know whether a datum transformation was applied for their output to a kmz, and thus impossible for me to know if I should apply one taking it out of the KMZ.

I'm pretty familiar with PFO/TBC and have both down cold depending on what you want your final export to be "in". Then there is the issue of what is your input datum, and how you are correcting the data. Your screen shots from PFO are absolutely correct. TBC also has the same exact ones. But, and I'll emphasize again is there is no way around testing on control set to the output you want to be "in". I've trained hundreds, and every student by the 3rd day doesn't get "it" until they plop their data onto a point in ArcMap and they are 1.5 meters away, while the other students are 10cm away. Your getting bit by thee most common confusion in GIS today. Thank god we got Melita, but you can imagine her inbox from all over the world. Your original question is very specific to handling in TBC, PFO.

So, I don't even want to guess why you want to be in "WGS84". If your in State Plane, your an obvious US citizen, so most common is you want to be in NAD83, and since your using top dollar GPS devices, you most specifically want to be "in" NAD83 (2011) Epoch 2010.0. Thats what you get when you run OPUS or PFO with a CORS base station and you use the reference from Base file. You have with each software, 2 datum gates you must pass thru, and thirdly ask what you are setting in ArcMap. So that is a 3x3 matrix or 9 possible combinations. You can't do this correctly without TRUTH. You must calibrate your GPS work, and Accuracy means doing the right thing with datum. You can't evaluate Accuracy without comparing to TRUTH, and its so darn easy these days to set a nail, occupy with a GPS running 2 hours and comparing.

Oh, and your last comment on KMZ production. Nothing in Google Earth ever is to be trusted. I wouldn't export data from 2,000$ software just to be compliant with GE. Export to NAD83 (2011) and let others suffer with any supposed shifts in GE.

Previously, customers registered for and logged into the Learning Center (LC), learn.transportation.trimble.com, using their company email address and access code. We have streamlined this process to make it more efficient to access the site. Now, Trimble customers will access the LC via TID. You will no longer be able to log in using your username and password.

Trimble ID enables a user to access most Trimble subscription products with a single set of login credentials. Implementing TID in our Learning Center allows for a more seamless login experience that aligns with many of your other Trimble subscription products, making us easier to do business with. Finally, single sign on, along with multi-factor authentication, improves our site security.

Entrepreneurs and innovators like Charlie Trimble, Javad Ashjaee and Dr. Benjamin Remondi (the father of GPS kinematic principals) capitalized on this technology. The cost for one GPS receiver when they hit the market in the late 1980s was about $100,000. Three GPS receivers, software and state-of-the-art computers were needed since most of the survey applications required GPS static survey methodology, creating a half million-dollar investment on equipment alone and resulting in only a handful of companies adopting this emerging technology. But those who did became pioneers and industry leaders.

My employer at that time was Mangini and Associates in Pueblo, Colo. Having worked for the progressive thinking BSC Group, I was versed enough in GPS technology to talk company management into buying an RTK system. I felt like a spaceman with my backpack, Trimble 4000 GPS receiver, GPS antenna, whip radio antenna, extension poles, heavy camcorder batteries and cables. Early RTK receiver technology suffered from limitations. The most notable was range or distance from base station to rover. Most manufacturers RTK systems specified positioning performance as 1 cm + 1 ppm RMS HZ x 2 cm +2 ppm RMS VT. The parts per million (PPM) component plays an important role later in this article.

Trimble owns and operates a network of terrestrial tracking stations strategically placed around the globe. These stations receive data broadcast by all GNSS satellites (GPS, GLONASS, Galileo, BeiDou, QZSS) and are the basis for a precise global modeling campaign including GNSS satellite orbit, clock, and atmospheric errors. This data is then sent to the RTX control center and processed. The RTX control center transmits the processed data to two entities. One: IP/cellular. Two: the processed data is also up-linked to geostationary L-band satellites. The L-band satellite then broadcasts correction data to the end user in the field providing real-time cm level positioning without the need for a base station, UHF radio, VRS/RTN connection nor internet connectivity.

Trimble CenterPoint RTX yields centimeter accurate positioning. However, not all applications require these accuracies. Trimble RTX offers a complete portfolio of solutions based on accuracy specifications (to see the range of RTX performance levels offered, visit HERE). Regardless of the tier being used, all data collected from multiple disciplines would be rendered on the same global datum. For national, state, county and city entities, this could be huge. For the private sector surveyor, the benefits are significant considering the time saved not having to setup and breakdown a RTK base station, not counting the liability of leaving the station unattended. To validate the concept that a Trimble CenterPoint RTX solution will yield similar results to other legacy correction sources, I conducted a very basic test on one point. Prior to the December 2020 release of Trimble Access 2020.20, I utilized ITRF 2014 (2010) values in my testing. Since the recent incorporation of displacement models in Trimble Access (previously mentioned in this article), the test was conducted in NAD 83 (2011). Another point worth mentioning, as with RTK, RTX observed data renders not only HZ and VT precisions values but a full covariance matrix as well (QC2 in Trimble Access settings).

Trimble CenterPoint RTX solves most of these problems, bringing seamless accurate and repeatable geodetic control to all crews throughout the continental United States and Southern Canada. Naturally, if tight vertical control is required, a combination of RTX and RTK or differential level analysis could be incorporated as part of the project workflow and Standard Operating Procedures.

Bob Green, PS, is a multi -generation land surveyor with more than 42 years of experience. For the past 17 years, he has provided sales, support and training for Trimble Navigation GNSS receivers, robotic total stations, 3D scanners, and lidar and survey software. Bob has been a positioning consultant to numerous government agencies including the U.S. Air Force Space Command, U.S. Marine Corps/Department of Defense, U.S. Border Patrol, Army Corps of Engineers, Homeland Security (FLETC) and NASA. Bob is employed by Frontier Precision and is a well-known public speaker and measurement technology advocate. Bob is currently working on several research and development endeavors to streamline and improve functionality to legacy geospatial workflows.

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