Surveys · 29 October 2026
Why ground control points matter
A drone knows roughly where it is. A survey needs to know exactly. The gap between the two is a handful of painted targets and a very good GPS.
By Arit, survey lead · Issue 11 · November 2026
Part 1
Roughly is not good enough
The GPS in a drone is accurate to a few metres. That is fine for a photo, but on a map a few metres can move a boundary onto a neighbour’s land or put a drain on the wrong side of a road.
Ground control points fix that. They are targets on the ground, measured with survey grade GPS to a centimetre or two. In processing, the map is pinned to those points.
Part 2
How many, and where
For a simple site we use at least five: one at each corner and one near the middle. Long road corridors need one every few hundred metres. Hilly sites need points at high and low ground, or the heights drift.
We also keep one or two check points that are not used in processing. If the map agrees with them, we know the accuracy is real.
Five painted squares and an hour of careful work turn a picture into a measurement.
Part 3
What it means for you
With control, a map is good to about 3 centimetres across and 5 up and down. Without it, expect a metre or more. For a land purchase, a design or a dispute, ask for control. For a listing photo, you do not need it.
Our map quote includes control for every orthomosaic, contour and volume output.
