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Mission Planning Large areas & GCPs

So far, any missions that require multiple flights I have broke down into mini missions, used GCPs and targets, and flew them twice to ensure I’ve got all I need, as it’s faster to fly it twice then reset targets.

Whats everyone thoughts, would it be more beneficial to have more targets, loosen my overlaps to cover more area and flight it multiple times and merge them?  could this not result in some uncalibrated images possibly?

And when using GCPs I just need 3 GCPs per flight, not necessarily 3 GCPs overlapping between flights correct?  these GCPs would be RTK quality.

Hey Richmond

I do break large mapping areas into smaller chunks, but I don’t put GCP for every little chunk. I would put many GCPs for the entire area and the go with single pass but high overlap flights 80% by 90% is what I usually use, but the challenge is you end up with lots of picture hence lots of processing time. I just wish somebody came up with better processing algorithm that would would require only 25% or less overlap, this would improve things alot. As it is now it is really difficult to process large areas.

Clarence

Richmond, 

We mostly do oblique image acquisition and smaller scale projects of homes and such, but when we do larger projects we keep the same overlap parameters as the smaller ones. We have found (and are in the process of publishing material it) that 70% overlap is a minimum for a quality project and that the best projects have a 90% overlap. Our image capture is not manually controlled from the ground and has to be set as a timed process beforehand so that our images are taken every “x” seconds. We use this, and knowledge of how big the area is, to fly at a certain speed and constrain the movement of the drone with its onboard GPS. This has worked well for us in every project we have had. We also use at least 8 GCPs.

As far as the overlap of GCPs, I do not think it is necessary to have the same ones for merging flights since each project will have a specific calibrated location from the GCPs included in it. When the program matches that project so a certain site on Earth and the other projects as being adjacent to it, even if the GCPs are not the same and do not overlap, it should be able to run properly and give you an accurate project. We have not tried this, but this is what I can say from what I assume to be true from similar experience. 

Travis

Thanks for the responses! Travis, I think you are correct, I have done what you are saying, but there has been some photo overlaps from mission to mission, so once I merge the projects I update the image tie points from one project to the next, it so far has produced good results for us.  

For our current demand from clients we are talking multiple square miles of mission area.  Very time consuming establishing GCPs (should went with the RTK) in each 1/4 section for each flight, what I would like to do is have our 5 or 8 GCPs established for the whole section per say and fly our multiple missions (as opposed to fly, move targets, fly, move targets, etc) so not necessarily every flight will achieve 3 gcps minimum, but the project as a whole would have the minimum, but I’ve been having troubles locating any information if this would be successful in the post processing.