Setting Up a Local Site Calibration From a Topcon .gc3 File
If you use Topcon surveying equipment on your site and operate in a local grid system, you should have access to a Topcon control point file (.gc3) from your rover or software suite.
This file type can be opened with Topcon's 3D office software, and the parameters from the calibration can be copied into Propeller's Site setup flow to set up your site for local processing.
Start by clicking Create a new site in the Propeller Sites page (below) or in the beginning of the Create new dataset flow.
Proceed through the Site setup wizard to the Coordinate System setup step, choose Local grid system, and select your .gc3 file.
Open your .gc3 file with Topcon 3D Office software by opening the program and importing your control file. Once the file has loaded, it is possible to find the calibration parameters in the file by going to the Project dropdown and selecting Control points... as below.
Important: Please first check if your local site calibration uses a geoid. This can be determined by checking the Coord. System tab and checking the "Use geoid model" field. If this is not blank, please discontinue this flow and contact Propeller Support.
Select the Localization tab in the dialog (seen below). This shows the values that need to be copied directly into Propeller. Note that the latitude and longitude have been obscured for privacy.
These values can be copied into Propeller by double-clicking on the fields, right-clicking and clicking Copy. They need to be copied into their corresponding fields as below. Be careful to select the right distance and angular unit in which values are expressed in 3D Office.
Once all fields have been entered correctly, click Save.
We now require that a test point is entered so that we can validate that the local to global transformation is being calculated correctly.
Enter a local Easting/Northing/Elevation (optional) from the list of control points in your .gc3 file. These can be accessed by clicking the Control points tab in the same dialog in Office 3D, as below.
Double-click one of the points which has a H.Error and V.Error value (i.e. the point was used in the calculation of the calibration). The dialog shown on the right will appear, exposing the local and global coordinates. (Again note that the lat/lng has been obscured.)
Copying in the Northing/Easting/Elevation in your local system will show a map with the corresponding global position of your point, as below.
You must also enter the corresponding global (latitude/longitude/height) values of the chosen point so that we can check the transformation result.
If we cannot transform the point correctly, the below error will show.
Please double check that all numeric values have been copied over verbatim (including minus signs, where applicable).
Note: If your calibration uses a geoid, the global height coordinate will not be correct. Please discontinue and contact support.
If the conversion result is still not correct:
Sometimes the value for Rotation is shown as a positive value in 3D Office, even though it is required to be a negative value. Please try adding (or removing) a minus sign to the value in the Rotation field in the form.
If this does not solve the problem, please contact support.
If the transform is correct, click Next. This will finalize the setup of your local system.