Using UAV photos to create DEM examples

[JPW]

Hi,

I just installed the Ames Stereo Pipeline and it looks like it can create DEM's from low elevation UAV imagery. However I have not found any examples for this use case.

Are there examples or can someone specify a workflow that can get me started on my project to reconstruct a DEM from around 500 photos captured from a DJI drone?

Thanks,

J

[Scott McMichael]

The closest you can find in our manual is section 9.3 about solving for camera positions for an aircraft mounted camera.  For UAV imagery the main challenge is to create camera models for each image you want to use.  First you will want to get an accurate distortion model for your camera.  If you don't already have one you can create one using camera_calibrate, see section A.33 in the manual.

If your drone records some sort of navigation information you will need to find a way to convert that into ASP camera files, described in section D.1 of the manual.  If not you will need to use the camera_solve tool to obtain local coordinate estimates for each image.  To create a DEM (and not just a point cloud) you will need an absolute reference such as ground control points.

Once you have camera models with position for each image, then you can start running stereo on individual camera pairs to create DEMs.  When all of the DEMs are finished you can combine them with dem_mosaic.  Most likely you will run into problems doing this and find you need to tweak the DEM alignment or something in order to get a good final DEM.  Feel free to post questions as you go through the process, ASP has not been used for this sort of work until recently and the process is not as easy as using ASP for satellite images.

Scott