What Are GCPs?
In short: Ground control points are large marked targets on the ground, spaced strategically throughout your area of interest. If you use ground control points with your aerial map, you first need to determine the RTK GPS coordinates at the center of each ground target. The ground control points and their coordinates are then used to help drone mapping software accurately position your map in relation to the real world around it.
It might be helpful to think of your GCPs as a series of thumbtacks placed on your drone map. Because the drone mapping software knows each of these thumbtacks’ exact locations, it can reference their locations when it matches up all of the other points on the map.
When to Use GCPs for Your Drone Maps
When used correctly, ground control points significantly improve the global accuracy of your drone map. Basically, they help ensure that the latitude and longitude of any point on your map corresponds accurately with actual GPS coordinates. This is important in situations where precision mapping and true global accuracy are needed, like in surveying or construction - terrain modeling and stockpile management are common use cases here.
Each drone mapping project is unique, and not all projects require a high level of global accuracy. Because of this, it is important to assess each project individually before you decide to take the extra step of using GCPs. But generally speaking, projects like geo-referenced overlays, design documents, and land title surveys benefit from the use of ground control points.