Advice on GCPs versus CPs

[KatyAppleton1]

I'm new to Drone2Map (but experienced with Pro), using version 2026.1.0.

I've been given access to some existing data I can use for testing, comprising approx 800 images and 5 GCPs, covering a 600 m by 250m area:

I completed the tutorial for 2D products and am now applying the same workflow to my data, creating a DSM and ortho.

I'm unsure of how to split my five known points between GCPs and checkpoints. Any advice? The survey area is a cliff, so there are 2 points on the beach (-1.5m approx elevation) and 3 on the cliff top (45m). Is the lack of points a big problem? I know this is going to take several hours to run so I want to get it right first time as far as possible.

I can feed back to our drone team about the number and arrangement of GCPs used when flying in future, if there are improvements that could be made. Constraints are that we cannot damage crops, so no points inside the fields, and the cliffs are unstable so none there either. 

[MarkBarker1 · Accepted solution]

Hi @KatyAppleton1 ,

You are correct, we typically recommend at least a minimum of five control points for a project. You could use 3 but its going to really affect the adjustment and accuracy considering the layout of the points. The coverage of your 5 points looks good, so running them all as GCPs you should get the best results.

In the future, I would ask the field team to capture at least double the number of points so you can make half of them checkpoints. Alternatively, if you are using an RTK drone you can restrict the adjustment to the GPS values of the images since they would be assumed accurate, something you would still want to verify in the metadata as a best practice. Then any points collected alongside the RTK drone flight could be used as checkpoints.  

Regard,

Mark

[KatyAppleton1]

Thanks - I'll run with all five as GCPs and make sure we have more points in future (not currently using an RTK drone).