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Author Topic: Using Global (ASTERDEM) as ground control points?  (Read 4266 times)

ferdywallinx

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Using Global (ASTERDEM) as ground control points?
« on: August 10, 2016, 11:22:33 AM »
I am having problems with my DEM. The details are mostly correct but i get convex/concave dems and large rifts when using photoscan for dem generation from aerial imagery. Would it be valid to use the global dem (Aster DEM or worldDEM V3) as ground control points without manual correction? If so what would be the correct processing method?

What i have done before is extract a ground control point for every 30 meters and loaded these values as ground control points. However, when i optimized camera's based on the ground control points my whole sparse point cloud would tilt way too much and neither the camera's nor the ground control points would still be in the bounding box.

Arie

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Re: Using Global (ASTERDEM) as ground control points?
« Reply #1 on: August 10, 2016, 07:19:38 PM »
Quick answer: Not, it won't be valid.  :P

This is mainly due to the accuracy and resolution of AsterDEM (and probably wordDEM too). According to the specs, the AsterDEM has a accuracy in the range of several meters. http://www.jspacesystems.or.jp/ersdac/GDEM/ver2Validation/Summary_GDEM2_validation_report_final.pdf

And if you take a critical look at the accuracy assessment, they compare it to SRTM. These datasets do not nearly achieve the same resolution and accuracy as aerial imagery.

You should rather try to find out why your DEM is concave/ convex. 10 minutes of googling will help you out ;)
Cheers.

ferdywallinx

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Re: Using Global (ASTERDEM) as ground control points?
« Reply #2 on: August 22, 2016, 04:11:10 PM »
well I did the 10 minutes of googling plus an extra long post here on this forum, so if you have any tips here Arie, that would be great  :)