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Author Topic: DEM export fails  (Read 9779 times)

jan

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DEM export fails
« on: July 25, 2011, 05:27:03 PM »
Hi,

I've just generated a 3D model of 1500 pictures (it looks good), calibrated with 3 ground marks.

However the DEM export is not correct. It gives a result (a dem), but the shape and the DEM values do not reflect the 3D model? The orthophoto export on the other hand works correctly.

What could be wrong? I never had a problem thus far with DEM export.

Thanks!

jan

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Re: DEM export fails
« Reply #1 on: July 25, 2011, 05:39:51 PM »
the aforementioned dem and orthophoto are in attachment

jan

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Re: DEM export fails
« Reply #2 on: July 26, 2011, 12:17:51 PM »
again for an other model more or less the same problem with the dem.

The dem is calculated very (too?) fast (in a second), but is just wrong.

Anybody an idea?

in the past I had no problems with dem calculation.
Maybe it is a bug in the latest version?
Or maybe I'm doing (seeing) something wrong?

Alexey Pasumansky

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Re: DEM export fails
« Reply #3 on: July 26, 2011, 12:20:37 PM »
Hello jan,

Does this problem occurs every time in the last build?
Best regards,
Alexey Pasumansky,
Agisoft LLC

jan

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Re: DEM export fails
« Reply #4 on: July 26, 2011, 12:21:51 PM »
for me: yes,

but built only 2 models with last built (see above)
« Last Edit: July 26, 2011, 12:24:05 PM by jan »

jan

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Re: DEM export fails
« Reply #5 on: July 26, 2011, 01:06:15 PM »
OK,

I found the answer.

there is no bug (I was (again) seeing something wrong)

However it was not very obvious at first sight.

It seems that the DEM extrapolates values so that it can fill all DEM values in a square which includes the mosaic shape (see attachment were I overlapped the DEM with a semi-transparant orthophoto).

I think that in the previous versions of photoscan DEM values were not extrapolated.

Alexey Pasumansky

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Re: DEM export fails
« Reply #6 on: July 26, 2011, 01:21:32 PM »
Hello jan,

If I understand your case right, you are using "Smooth" reconstructing method. In this case geometry is extrapolated up to the borders of bounding box and DEM is built on this extrapolated volume.
If you use "Sharp" reconstructing method there will be no geometry extrapolation as well as no DEM extrapolation.
« Last Edit: July 26, 2011, 01:37:00 PM by Alexey Pasumansky »
Best regards,
Alexey Pasumansky,
Agisoft LLC

jan

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Re: DEM export fails
« Reply #7 on: July 26, 2011, 02:00:17 PM »
Hello Alexey,

that makes sense,

thanks,

Jan

jan

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Re: DEM export fails
« Reply #8 on: July 26, 2011, 08:12:47 PM »
Hi Alexey,

When I want to rebuilt geometry with 'sharp' reconstruction mode after having built geometry with 'smooth' reconstruction mode already, Photoscan crashes each time after loading photos.

Is it not possible to overwrite the geometry building process then?

If so, is is then possible to delete the geometry building already processed?

otherwise I have to rerun also the alignment process which is 100% as I want it,

thank you,
Jan

Alexey Pasumansky

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Re: DEM export fails
« Reply #9 on: July 27, 2011, 12:55:23 PM »
Hello Jan,

We are planning pre-release version of PhotoScan 0.8.3 today or tomorrow. We'll ask you to test if new release still crashes on this set, when building sharp geometry.
Best regards,
Alexey Pasumansky,
Agisoft LLC