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Author Topic: Why is exported DEM so much smaller than OrthoMosaic?  (Read 5379 times)

nickponline

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Why is exported DEM so much smaller than OrthoMosaic?
« on: May 31, 2014, 02:49:10 AM »
I'm exporting my DEM and Ortho using:

blockw, blockh = 4096, 4096

chunk.exportOrthophoto('ortho.tif', blockw=blockw, blockh=blockh, color_correction=False, blending='mosaic', write_kml=True, write_world=True, projection=chunk.projection)

chunk.exportDem('dem.tif', blockw=blockw, blockh=blockh, write_kml=True, write_world=True, projection=chunk.projection)

I get many ortho-x-x.tif images each 4096x4096 but only a single dem.tif which is 4096x4096 and the DEM uses only the top left of this image?

Alexey Pasumansky

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Re: Why is exported DEM so much smaller than OrthoMosaic?
« Reply #1 on: May 31, 2014, 01:53:53 PM »
Hello nickponline,

You can specify the same resolution using the corresponding argument. However, the effective resolution of DEM depends on the reconstruction quality used. While for orthophoto it is usually close to original resolution of photos.
Best regards,
Alexey Pasumansky,
Agisoft LLC

nickponline

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Re: Why is exported DEM so much smaller than OrthoMosaic?
« Reply #2 on: June 04, 2014, 01:32:24 AM »
If you look at my code above you will see that I did specify the same resolution. What settings during the process would effect the resolution of the final DEM.

Alexey Pasumansky

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Re: Why is exported DEM so much smaller than OrthoMosaic?
« Reply #3 on: June 04, 2014, 10:13:48 AM »
Hello nickponline,

You've specified only block size and there's nothing about export resolution (similar to m/pix field in export orthophoto/DEM dialog in GUI).

Best regards,
Alexey Pasumansky,
Agisoft LLC

nickponline

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Re: Why is exported DEM so much smaller than OrthoMosaic?
« Reply #4 on: June 06, 2014, 10:43:45 AM »
Hi Alexey,

Thanks for the reply. Won't it default to the GSD like exportOrthophoto does?

Alexey Pasumansky

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Re: Why is exported DEM so much smaller than OrthoMosaic?
« Reply #5 on: June 06, 2014, 11:18:21 AM »
Hello nickponline,

Default export resolution is different for orthophoto and DEM export (you can check it in the corresponding export dialog). Effective orthophoto resolution is close to the effective resolution of the original images, whereas default DEM export resolution depend on the model reconstruction quality.
Best regards,
Alexey Pasumansky,
Agisoft LLC