Forum

Author Topic: Why can I not select 'Build DEM'?  (Read 7995 times)

DanilBor

  • Newbie
  • *
  • Posts: 8
    • View Profile
Why can I not select 'Build DEM'?
« on: February 07, 2018, 02:45:18 PM »
Hello,

I just updated to 1.4 and face a problem I have never seen before:

I create orthomosaics of aerial pictures and my usual workflow goes like this: import images, allign photos, import GCPs, Point Cloud Optimization, Dense Cloud Generation, DEM generation.. and so on.

I have done all steps until DEM generation, but I am now unable to select the 'Build DEM..'" function. I have done several orthomosaics already and usually I was always able to create a DEM after having generated a dense cloud, so I really have no clue what could have happened. Could this be related to 1.4?

Can somebody give me reasons why I cannot select 'Build DEM..'? What I noticed during my work flow:

I had problems with point cloud optimization for this specific chunk. The input images are relatively low resolution, because I want to use this one as a mere background image for reference. I deleted points with high reconstruction uncertainty, high reprojection error and low projection accuracy, but I did NOT optimize cameras, because it completely ruined my alignment as soon as I tried.. which is due to the low quality of the input images I assume.

Could the missing Camera Optimization be responsible?

Thank you very much

Alexey Pasumansky

  • Agisoft Technical Support
  • Hero Member
  • *****
  • Posts: 14813
    • View Profile
Re: Why can I not select 'Build DEM'?
« Reply #1 on: February 07, 2018, 02:59:44 PM »
Hello DanilBor,

The chunk should be georeferenced or scaled in order to use Build DEM function ([R] or [S] mark next to the chunk's label in the Workspace pane). Alternatively, it would be also available, if you apply all three manual transformations fo the chunk: Rotate Object, Scale Object, Move Object.
Best regards,
Alexey Pasumansky,
Agisoft LLC

DanilBor

  • Newbie
  • *
  • Posts: 8
    • View Profile
Re: Why can I not select 'Build DEM'?
« Reply #2 on: February 07, 2018, 06:03:36 PM »
Thank you very much, Alexey.

I fixed the problem, but I am still confused about why I had it in the first place, because my GCPs had geographic coordinates within a defined coordinate system. So the solution for my problem was to enable the boxes for camera reference and marker reference in the reference settings..

As this is the first time, that this has happened to me: Does this step has to be done manually each time in the new version? With 1.3 I never had to manually check these boxes.

Thanks for helping so quick

Alexey Pasumansky

  • Agisoft Technical Support
  • Hero Member
  • *****
  • Posts: 14813
    • View Profile
Re: Why can I not select 'Build DEM'?
« Reply #3 on: February 07, 2018, 06:08:28 PM »
Hello DanilBor,

For georeferencing it's necessary either to have the coordinate information for at least three aligned cameras (have their coordinates in the Reference pane - all these cameras should be checked on in the pane), or have the coordinates input for at least three markers - all of them should be checked on in the Reference pane and should have at least two projections on the cameras from the aligned sub-set.

So probably the markers that you were using had insufficient number of projection or were not checked on in the Reference pane.

Also note that you need to press Update button on the Reference pane to apply the available coordinate information from the checked on instances.
Best regards,
Alexey Pasumansky,
Agisoft LLC