Cant align photos

[jbd@tvilum.dk]

Hi,

I have done a flight in an area with a lot of forrest. The problem is that Aigisoft Photoscan cant align the photos in the areas with many trees (see the attached file).
What do I do?
Can I do some manual aligning pointing put control points?

[Alexey Pasumansky]

Hello Jacob,

The problem might be related to the insufficient overlap for the area covered by the dense forest.  I can suggest to try alignment with the disabled preselection to see if more images can be matched.

In principle oyu can use markers as valid matching points, but at least four markers should be placed on each Not Aligned image.

[jbd@tvilum.dk]

Hi Alexey,

Thanks for your reply. There is an overlap of 60-70 % at ground level. I think the problem is the complexity of the tree structures and the height of the trees. The trees is maybe 20 m heigh so the actual flying height above the trees is 50-20 = 30 m.

I have now flown the project again in 80 m height. The alignment is much better now. The problem is that i didnt places any GCP on the second flight. Is it possible to use the pictures from the first flight (with GCP) combindes with the second flight (without GCP)?

[Alexey Pasumansky]

Hello Jacob,

If you can find the positions of the GCPs in the second set, then you can use them. However, I think that the measurement accuracy should be lowered, if there's bare ground instead of GCP mark.

[jbd@tvilum.dk]

Hi Alexey,

I cant find the GCP in the second flight, but couldnt i just leave the markers as grey flags in the new pictures?

[Alexey Pasumansky]

Hello Jacob,

Grey flags are not used in the processing, so you need to adjust the projections and turn them into blue/green flags in order to use markers for optimization/referencing.