How do I place Ground control point(GCP)/Checkpoint(CHP) markers?

Question

How do I place Ground control point(GCP)/Checkpoint(CHP) markers?

Answer/Cause

Please follow the guidelines below.

・Place the markers inside the drone's planned flight area, so that each marker appears in a sufficient number of overlapping photos.

・Distribute the markers around the perimeter of the target site to provide good geometric coverage of the survey area. Concentrating markers in one region will reduce accuracy.

・When using GCPs, at least 3 markers are required, and 4 or more are recommended for better accuracy.

・Measure the center of each marker using a GNSS rover or another high-precision surveying device. Note: Insufficient measurement accuracy will directly degrade the reconstructed output.

Tips for higher accuracy

・Flight coverage: Extend the flight plan at least one flight lane beyond the outer edge of the target area, so that the entire target is captured with sufficient overlap (not only at the edge of the flight envelope).
・Number of GCPs: 3 is the minimum; 4 or more is strongly recommended.