TPC 2026 - Calibrating GPS/GNSS Data

Calibrating GPS/GNSS Data

To use existing survey, real time, in the field with GPS/GNSS, the survey data needs to be on the GPS/GNSS CRS.

If your GPS/GNSS data is on the same CRS as your survey, they can simply share data.

However, to use GPS/GNSS data with an existing survey that doesn't use the same CRS as your GPS/GNSS, you will need to calibrate the two.

•Your GPS/GNSS data controller may have the ability to calibrate data in the field.

•If not, you can use TPC to calibrate the two. This topic discusses this work flow.

Creating a Traverse with Calibration Points

If you can observe two or more of a survey's control points using GPS/GNSS, you can calibrate the survey and GPS/GNSS to each other. Three or four point pairs that encompass the entire project area is best. See Select a traverse of uncalibrated points.

Here is an example.

Point          Description
201          =1
202          =2
203          =3

•In this example, observed GPS/GNSS points 201, 202 and 203 correspond with existing survey points 1, 2 and 3.

•A calibration can be created from this traverse, either calibrating the GPS/GNSS to the survey or the survey to the GPS/GNSS, depending on the work flow you choose. See Calibrating GPS/GNSS to Your Survey and Calibrating Your Survey to GPS/GNSS.

•After the calibration is applied, you can check the fit via the Stakeout Report, using this same traverse and telling TPC to subtract 200 from points 201, 202 and 203 to find their comparable points.

Calibrating in the Field

Depending on your GPS/GNSS equipment, you can do all of this in the field.

•Export the GPS/GNSS points to a laptop with TPC. This can be done via the cloud with a cell phone, blue tooth or a direct cable connection.

•Create the calibration.

•Export calibrated survey data back to your GPS/GNSS equipment.

Working with Calibrated Survey Data

Now that you have survey data calibrated to your GPS/GNSS you can continue to

•search for existing monuments you haven't located yet

•do stakeout

•collect site / topo / boundary data

To use existing survey, real time, in the field with GPS/GNSS, the survey data needs to be on the GPS/GNSS CRS.

If your GPS/GNSS data is on the same CRS as your survey, they can simply share data.

Here is an example.

Depending on your GPS/GNSS equipment, you can do all of this in the field.

Now that you have survey data calibrated to your GPS/GNSS you can continue to

Eventually, you will probably export all of this back to TPC and the calibration will once again coordinate the survey with your GPS/GNSS data.