DDMS – Applying Ground Refinement Points

Ground Refinement Points (GRP)s can be applied after a mission is processed in order to improve the geolocation of a mission’s orthomosaic and DEM. Other apps processed based on these will also have the updated coordinates. This can be useful in cases where alignment with a previous mission or with Google Maps imagery is desirable.

To apply GRPs to a mission, find the Ground Refinement Points app and click “Pick Ground Refinement Points”. In the popup window, first select how you’ll enter your GRPs. You may enter the coordinates manually (in WGS-84), pick points on Google Maps or pick points on another mission from your account. In this view, the left side of the window is the current mission that will be adjusted to match the desired coordinates, and the right side shows the map or table that will be used as reference to make the change.

To enter coordinates manually, select the option from the dropdown and then add a point. Locate the point visually on the map then enter the exact coordinates for each point. You can click on each coordinate in the Map Viewer to identify which point it is if necessary.

To reference either Google Maps imagery or another mission, select the desired reference source and then add points one-by-one. Use points away from the edges of your mission as these areas may not be located as accurately as the main mission area. Try to use reference objects located on flat surfaces away from edges where possible. The corresponding markers are colored to match, and can also be identified by clicking on the marker.