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DEM Band Value Incorrect

  • August 6, 2018
  • 13 replies
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tbs_gis_team
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I am having issues with FME reading the Band Value incorrectly or applying a conversion.

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13 replies

takashi
Celebrity
  • August 6, 2018
Could you please attach a sample DEM dataset and a workspace which reproduce the issue?

 


tbs_gis_team
Contributor
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  • August 7, 2018

File is too large to attach. I could email if you want to take a look at it...

Thank,

Chad


takashi
Celebrity
  • August 7, 2018

File is too large to attach. I could email if you want to take a look at it...

Thank,

Chad

It's enough to attach only a small sample data that can reproduce the problem. Consider using the Clipper or the RasterTiler to make a sample.

 

 


tbs_gis_team
Contributor
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  • August 8, 2018

I will clip a portion and send...

CK


tbs_gis_team
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  • August 8, 2018

When I clip in FME it gives this error:

USGS_DEM Writer: The maximum number of decimal places allowed for the format attribute 'dem_spatial_resolution_z' when expressed in 'FEET' is 1. The value '0.0014411999999999999' must be reduced to 1 decimal place(s)

A fatal error has occurred. Check the logfile above for details

... Last line repeated 2 times ...


tbs_gis_team
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  • August 8, 2018

tbs_gis_team
Contributor
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  • August 8, 2018

the attached zip the band is at a zero precision, that is the only way I could clip and export. The attached screen shot shows what the elevation should be in this area. Let me know if this helps.correect-elev.png


takashi
Celebrity
  • August 8, 2018

the attached zip the band is at a zero precision, that is the only way I could clip and export. The attached screen shot shows what the elevation should be in this area. Let me know if this helps.correect-elev.png

Interpretation of the clipped raster is Int32, whereas the original interpretation shown in your screenshot is Real64. The change of interpretation is the direct reason why cell values have been rounded into zero precision. Is it the original issue - "DEM Band Value Incorrect"? If so, we will have to investigate your workspace to clarify why/when the interpretation has changed.

 

 


tbs_gis_team
Contributor
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  • August 8, 2018

If you want to take a look at the original DEM here is the link:

ftp://data.ga.lsu.edu/lidar/2000_state/la_lidar_dem/2909001ne_dem.zip

The attached shapefile is of the area of interest that the screen shot I sent shows elevation of -0.3' and FME reads different. When I clip the DEM it changes the value so I cannot send a clipped area of the DEM.

Thanks,

Chad

dem-clip.zip


tbs_gis_team
Contributor
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  • August 8, 2018

fme-screenshot.png


nampreetatsafe
Safer
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Hi @tbs_gis_team,

Thanks for reporting this to us and providing your sample datasets. A developer confirmed that it looks like our USGS_DEM Reader isn't applying the elevation of the local datum to individual elevation values within a profile. I've opened up a case for you, for which you should have received a notification email.

As a workaround for the provided dataset specifically, try using an Offseter to offset Z by -0.312000006437302. I hope that helps!

tbs_gis_team
Contributor
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  • August 14, 2018

Hi @tbs_gis_team,

Thanks for reporting this to us and providing your sample datasets. A developer confirmed that it looks like our USGS_DEM Reader isn't applying the elevation of the local datum to individual elevation values within a profile. I've opened up a case for you, for which you should have received a notification email.

As a workaround for the provided dataset specifically, try using an Offseter to offset Z by -0.312000006437302. I hope that helps!
Thanks for the information, let me know if the reader is updated. The process would be reading multiple files and not sure if that offset would apply to all datasets.

 

Thanks,

 

Chad

 

 


nampreetatsafe
Safer
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I'm glad to report that the fix for this issue has been included in the latest FME release (FME 2018.1.0.2, build 18547). Thanks @tbs_gis_team for bringing this to our attention, and for helping us make FME even better!