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Author Topic: DEM Grayed Out in Workflow  (Read 894 times)

dqattan

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DEM Grayed Out in Workflow
« on: December 11, 2017, 12:49:02 AM »
Hello,

I have a basic question: DEM is grayed out in the Workflow menu.  I believe I am missing something very basic.

Please advise, thank you.

D.Qattan

SAV

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Re: DEM Grayed Out in Workflow
« Reply #1 on: December 11, 2017, 03:28:04 AM »
Hi dqattan,

You have to first generate a sparse and/or dense point cloud in order to activate BUILD DEM in the workflow menu. As soon as you have aligned your images (= generated sparse point cloud) or computed a dense point cloud, it will be available.

Regards,
SAV

dqattan

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Re: DEM Grayed Out in Workflow
« Reply #2 on: December 11, 2017, 09:50:22 AM »
Hi SAV,

I have done both.  I've gone through the complete workflow, even built an orthomosaic, but still DEM is grayed out.  Any other ideas?

Thanks,
D.Qattan

Alexey Pasumansky

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Re: DEM Grayed Out in Workflow
« Reply #3 on: December 11, 2017, 10:06:53 AM »
Hello dqattan,

You need to reference your model before building the DEM. It seems that you haven't used neither camera location information, nor the coordinates of the ground control points.
Best regards,
Alexey Pasumansky,
AgiSoft LLC

dqattan

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Re: DEM Grayed Out in Workflow
« Reply #4 on: December 12, 2017, 04:08:10 PM »
Hello,

You are right, my camera (Sony Nex 7) does not support camera location and I am looking at creating GCP's.  But RTK equipment is very expensive, can you suggest a less expensive approach?

Thank you,
dq.

Alexey Pasumansky

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Re: DEM Grayed Out in Workflow
« Reply #5 on: December 12, 2017, 04:14:33 PM »
Hello dqattan,

If you do not require high level of precision, you can measure the GCPs with the common GPS device (performing several measurements for each point to minimize the error).

In principle, if you have several reference distances measured in scene you can use them as scale bar instances in PhotoScan (applying correct scale to the model), then adjust the model orientation relatively to the coordinate system axes in the bottom-left corner of the Model view (by eye) and then execute the following line in the Console pane of PhotoScan Pro window to emulate the georeferencing:
Code: [Select]
PhotoScan.app.document.chunk.transform.matrix = PhotoScan.app.document.chunk.transform.matrix
Best regards,
Alexey Pasumansky,
AgiSoft LLC