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How distribute GCPs for Multiple missions of a single overall project

Hi,

I have a decent sized project where I have to cover an area of 1.65 Ha with a Phantom 4 Adv at a height of 52 m. Which will require approximately 45 missions.
My question is, do I have to make 5 GCPs for each mission? or should I consider the overall area, and distribute say 45 GCPs over the whole 1.65 Ha area?
Not sure if I’m explaining it clearly, hope you get the idea.
Regards,
Diya

Anyone ?

Do you really mean 1.65 Ha, or is that a typo? Because that is a very small area. Will you be processing all 45 missions in a single project or multiple smaller projects, then merging? If a single project then you only need sufficient GCPs distributed throughout the entire area. 45 seems to be a lot. I would think 5-10 would be plenty. If you break it up into smaller projects, then you will need additional GCPs in the overlap areas, or manual tie points.

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Thank you for replying.
yes the area is equivalent to 1.62 km2.
I’m going to divide it into smaller projects then merge them.
so regarding the GCP, how many exactly do you recommend per small project at the overlap areas? and should they be placed on the corners or edges?

Regards

Hi Diya,
The number and location of project GCP’s is a frequent question and can be difficult to answer as every project is unique. The Nevada Department of Transportation did a test a while back (Pix4D Blog post, Do more GCPs equal more accurate drone maps?) and they found that more GCPs did not equate to more accuracy. I would avoid putting them near the edges of projects as it is best to have a good distribution of images capturing each GCP from various sides/perspectives.
Be mindful of getting sufficient overlap among your flights to facilitate keypoint matching. I suspect your project area will encounter varied lighting/environmental conditions during the 45 missions and having good overlap will improve the reconstruction.

Regards,
Aaron Woods

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