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This topic discusses how calibrations relate to a survey's Coordinate Reference System (CRS).
Depending on the CRS you select for your survey, a geodetic point of 43°54'19.429"N / 124°05'45.937"W would generate a grid coordinate of 836264.996Y / 3973780.945X when transformed. The distance between two such coordinates would be a grid distance. TPC would then use the Distance Type selected for a traverse, drawing or COGO routine to report the grid or ground distance of that inverse.
Many large area infrastructure projects, like DOT highways, pipelines, municipal / county / state lands survey use CRS coordinates to coordinate positions across the entire project. TPC is very comfortable with this kind of survey and has all the tools to keep grid and ground coordinates and distances separate.
Only CRS Coordinates Get Transformed
If you have local coordinates of 5000/5000 in a survey that has a CRS like UTM or State Plane, the coordinates would not produce valid geodetic positions because they are not valid for that CRS.
This comes into play when local coordinates are calibrated to the CRS. When this happens, their coordinates are valid for that CRS and can therefore be transformed into geodetic positions.
Creating a Calibration to the CRS
When you create a calibration to the survey's CRS, TPC automatically identifies that calibration as being to the CRS.
If you then apply that calibration to some survey data, TPC knows that data is on the CRS grid and is free to transform those valid CRS coordinates to their geodetic position without any further calibration.
Using a Site Calibration
If your common workflow is to calibrate imported GPS/GNSS data to your local survey grid, you will create a calibration to go from the GPS/GNSS geodetic positions to equivalent projection coordinates based on your survey's CRS, then to your local survey coordinates. The calibration you create does all of this for you. See Site Calibration.
If and when you choose to export back to your GPS/GNSS, TPC needs to first reverse calibrate local coordinates to CRS coordinates before it transforms them to their geodetic positions for export to GPS/GNSS. TPC knows to do this because the calibration know that it's calibrated coordinates are local not CRS.
Related Topics
Calibrating Data
Editions
Premium, Professional
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