Forum

Author Topic: DTM -32767 values  (Read 6523 times)

fpbv

  • Full Member
  • ***
  • Posts: 102
    • View Profile
DTM -32767 values
« on: May 16, 2012, 08:45:47 PM »
Hi guys

In the last version when you go to Export DEM has a box that says "Crop invalid DEM"
I check this all the time but my Geotiff files always comes with this values.
It give me a lot headaches to fix this in ArcGIS.
Any help?

Kjellis85

  • Full Member
  • ***
  • Posts: 218
  • Archaeological field supervisor
    • View Profile
    • Contact information at University of Tromsø
Re: DTM -32767 values
« Reply #1 on: May 20, 2012, 01:42:25 AM »
Hi guys

In the last version when you go to Export DEM has a box that says "Crop invalid DEM"
I check this all the time but my Geotiff files always comes with this values.
It give me a lot headaches to fix this in ArcGIS.
Any help?

I have dealt with the same issue. The best way to solve this is by using QuantumGIS. Can't remember the workflow here on the spot, but if this could be usefull to you, send me a PM.

Alexey Pasumansky

  • Agisoft Technical Support
  • Hero Member
  • *****
  • Posts: 13910
    • View Profile
Re: DTM -32767 values
« Reply #2 on: May 21, 2012, 03:30:38 PM »
Hello Fabricio,

"Crop invalid DEM" feature actually works in the way of substituting values for additional geometry (for example, created by Smooth method) by NoData values (user defined in Export DEM dialog). Since DEM is exported as raster values are present for all points but some of them may contain NoData.
Best regards,
Alexey Pasumansky,
Agisoft LLC

fpbv

  • Full Member
  • ***
  • Posts: 102
    • View Profile
Re: DTM -32767 values
« Reply #3 on: May 21, 2012, 04:51:57 PM »
Thanks Alexey

But is there a way to find this NoData values on the DEM?
I mean, how to fix this before export DEM?
Now I use that Quantum GIS way to solve, just convert the DEM to GDAL format and convert the -32767 values to 0.
It is not a tough issue procedure, but you always get more files than necessary.

Alexey Pasumansky

  • Agisoft Technical Support
  • Hero Member
  • *****
  • Posts: 13910
    • View Profile
Re: DTM -32767 values
« Reply #4 on: May 21, 2012, 04:59:27 PM »
Hello Fabricio,

No-data value could be changed in the corresponding edit box in Export DEM dialog.
If you wish you can set zero value there as well.
Best regards,
Alexey Pasumansky,
Agisoft LLC

Kjellis85

  • Full Member
  • ***
  • Posts: 218
  • Archaeological field supervisor
    • View Profile
    • Contact information at University of Tromsø
Re: DTM -32767 values
« Reply #5 on: May 24, 2012, 02:19:13 PM »
Thanks Alexey

But is there a way to find this NoData values on the DEM?
I mean, how to fix this before export DEM?
Now I use that Quantum GIS way to solve, just convert the DEM to GDAL format and convert the -32767 values to 0.
It is not a tough issue procedure, but you always get more files than necessary.

I have done this as well, and if I remember corectly there is a way to cut the DEM in QGIS so that you don't get any value what so ever where the no-value data used to be. It was a while back, so I don't remember the actual workflow.