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Author Topic: Serious problem with DEM and GIS software  (Read 3504 times)

scannapieco

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Serious problem with DEM and GIS software
« on: December 03, 2018, 08:57:24 AM »
Hello,
I have a serious problem to solve.
After generating the dense cloud, I create the DEM with a cartographic system like for example EPSG 25832 or EPSG 6707.
When I open the DEM with a GIS I do not see any information about the elevations z despite correctly seeing the DEM and its color mapping.
I tried to generate layer curves in Photoscan and generate them normally but I need to import the DEM into any GIS software (eg QGIS) and see the z quota information.
What could be the problem?
This is a link for the DEM:

https://drive.google.com/file/d/1c61IT2xsyOWjbz8KPCvbOEj5UU8Yrp5t/view?usp=sharing

Thanks a lot.
Alex


JMR

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Re: Serious problem with DEM and GIS software
« Reply #1 on: December 03, 2018, 11:46:06 AM »
It looks that you have exported a colour ramp rendered image, but not a proper DEM. I guess you may have used the CaptureView command rather than the export DEM.
Please right click on the DEM object in the project tree and choose Export DEM, (File-Export-Export Dem... is the same)

Cheers

scannapieco

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Re: Serious problem with DEM and GIS software
« Reply #2 on: December 03, 2018, 11:52:02 AM »
Dear Cheers,
NO....I exported DEM.
This the reason because I can't understand the problem.
I tried both with DEM in WGS84 both with a particular coordinate system.
Please help me.
Alex
« Last Edit: December 03, 2018, 11:56:30 AM by scannapieco »

BobvdMeij

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Re: Serious problem with DEM and GIS software
« Reply #3 on: December 03, 2018, 12:27:17 PM »
I just downloaded your DEM and found the same issue as you described when loading this into QGIS. Looking at the attributes it appears as if the DEM was exported like a 4-band orthomosaic rather than an elevation model.

Could you perhaps post a screenshot of your export-DEM settings? I'm thinking you may have set the parameter 'Raster transform' to Palette, as this will produce a 4-band DEM. This should be set to None instead.
« Last Edit: December 03, 2018, 12:35:43 PM by BobvdMeij »

scannapieco

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Re: Serious problem with DEM and GIS software
« Reply #4 on: December 03, 2018, 01:25:22 PM »
Yes,
I chose "palette"
See the attached screenshot ....
....
If I don't chose "palette" what parameter I have to set in the field marked in the screenshot?

BobvdMeij

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Re: Serious problem with DEM and GIS software
« Reply #5 on: December 03, 2018, 01:32:01 PM »
Yes,
I chose "palette"
See the attached screenshot ....
....
If I don't chose "palette" what parameter I have to set in the field marked in the screenshot?

Just set it to None for Raster Transform and leave the default value (-32767) for No-Data value untouched.

scannapieco

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Re: Serious problem with DEM and GIS software
« Reply #6 on: December 03, 2018, 01:57:28 PM »
Yesterday I also tried to generate the DEM without raster, as you recommend, choosing as a reference system WGS84.
I have decided to open it with QGIS, but even in this I do not see any quota information.
In these minutes I am regenerating the DEM with ETRS89 reference system without raster and leaving the data value unchanged.
I'll let you know if it works in QGIS.

scannapieco

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Re: Serious problem with DEM and GIS software
« Reply #7 on: December 03, 2018, 02:23:25 PM »
NO.
It doesn't work!
Please see attached file.....

Alexey Pasumansky

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Re: Serious problem with DEM and GIS software
« Reply #8 on: December 03, 2018, 05:41:36 PM »
Hello scannapieco,

Does it help, if you change the view mode of the "Identify results" frame from "tree" to "table"?
Best regards,
Alexey Pasumansky,
Agisoft LLC

scannapieco

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Re: Serious problem with DEM and GIS software
« Reply #9 on: December 03, 2018, 06:19:35 PM »
Hello scannapieco,

Does it help, if you change the view mode of the "Identify results" frame from "tree" to "table"?

NO,
also in "table" mode there isn't information about elevation.
I also tried with another DEM always created with Photoscan but about another project.
Please see the attached screen capture.
I don't understand because in Photoscan I can see elevation information and I can create countours but in GIS not.
Moreover in Cloud Compare I can see the correct dense colud but also creating DEM in Cloud Compare also here I cannot view infomation about heights.
Perhaps the problem can be the dense cloud.
please help me.
I can send to technical support the project files.
Alex

Alexey Pasumansky

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Re: Serious problem with DEM and GIS software
« Reply #10 on: December 03, 2018, 06:43:28 PM »
The latest screenshot is again related to "Palette" raster transformation applied to the exported DEM - it contains Red, Green and Blue channels and alpha-channel with the transparency. Can you please open the DEM exported without any raster transformations applied and check the "table" view mode in the "Identify results" frame?
Best regards,
Alexey Pasumansky,
Agisoft LLC

scannapieco

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Re: Serious problem with DEM and GIS software
« Reply #11 on: December 03, 2018, 09:19:00 PM »
The latest screenshot is again related to "Palette" raster transformation applied to the exported DEM - it contains Red, Green and Blue channels and alpha-channel with the transparency. Can you please open the DEM exported without any raster transformations applied and check the "table" view mode in the "Identify results" frame?

Is this?

BobvdMeij

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Re: Serious problem with DEM and GIS software
« Reply #12 on: December 03, 2018, 09:28:07 PM »
The latest screenshot is again related to "Palette" raster transformation applied to the exported DEM - it contains Red, Green and Blue channels and alpha-channel with the transparency. Can you please open the DEM exported without any raster transformations applied and check the "table" view mode in the "Identify results" frame?

Is this?

That's it! Seems you've figured it out after all ;)

scannapieco

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Re: Serious problem with DEM and GIS software
« Reply #13 on: December 03, 2018, 09:50:06 PM »
OK.
So for work with DEM generated with Photoscan in a GIS software it must be exported without raster palette.