Apply ASPRS ground control guidance for drone photogrammetry on boundary-adjacent topographic work

Steps

1. Set the target accuracy for the deliverable first, then size ground control accordingly — per ASPRS guidance, ground control point accuracy should be roughly twice as accurate as the target product accuracy, since GCP error propagates directly into the final model.
2. Establish GCPs using survey-grade static or RTK/RTN GNSS observations tied to appropriate published control, not consumer-grade GPS, since GCPs are the accuracy backbone of the entire photogrammetric model.
3. Distribute GCPs across the full project extent and at varying elevations (topographic highs and lows), with a common starting rule of roughly five well-distributed points scaled up to 8–12 or more for larger/more complex terrain — exact counts should be driven by project size, terrain relief, and required accuracy class, not a fixed rule.
4. Withhold at least one to two independent checkpoints (not used in the model's georeferencing solution) so the resulting model's actual achieved accuracy can be verified against ASPRS Positional Accuracy Standards using RMSE, rather than only reporting the model's self-reported internal error.
5. Where the topo work is adjacent to a legal boundary, keep the photogrammetric surface/GCP-derived data clearly separated in documentation from any licensed boundary determination — GCP-controlled UAS topo is not a substitute for boundary survey evidence even at high accuracy.