Add Control and Check Points

A Ground Control Point (GCP) is a base station with known coordinates. GrafNet computes positions of unknown points by transferring positions throughout the network using the processed vectors from control points.

Check points are points with known coordinates, but their positions will not be constrained in the network. Rather, they will be used only to check the difference between the known coordinate and the processed position for that point. Adding a minimal amount of control to your project (one 3D GCP) and then adding all other control points as check points is a good way to check the agreement between control points in your network prior to processing a fully constrained solution.

Follow the steps below to add a ground control point.

1. Select File | Add / Remove Control Point.

   Alternatively, you can right click on the station you want to add as a GCP and choose Add as Control Point. If you use this latter approach, skip directly to step 4.

2. Click the Add button.

3. Select the ID corresponding to the control point to be added.

   If the GPB file was converted from RINEX and coordinates were scanned from the RINEX header, these will be automatically loaded.

4. Enter or verify the coordinates and datum for that station.

5. Click the OK button.

   Repeat similar steps to add check points.