[Gdal-dev] some geotiff export problems
Frank Warmerdam
warmerdam at pobox.com
Mon Nov 25 00:43:53 EST 2002
Vladimir Slepnev wrote:
> 5) Here are some listgeo snippets.
>
> A "good" GeoTIFF file (not GDAL-generated):
>
> Keyed_Information:
> GTModelTypeGeoKey (Short,1): ModelTypeProjected
> GTRasterTypeGeoKey (Short,1): RasterPixelIsPoint
> GTCitationGeoKey (Ascii,25): "UTM Zone 37 N with WGS84"
> GeogLinearUnitsGeoKey (Short,1): Linear_Meter
> GeogAngularUnitsGeoKey (Short,1): Angular_Degree
> ProjectedCSTypeGeoKey (Short,1): PCS_WGS84_UTM_zone_37N
> End_Of_Keys.
> End_Of_Geotiff.
>
>
> A GDAL-generated file:
>
> Keyed_Information:
> GTModelTypeGeoKey (Short,1): ModelTypeProjected
> GTRasterTypeGeoKey (Short,1): RasterPixelIsArea
> ProjectedCSTypeGeoKey (Short,1): User-Defined
> ProjectionGeoKey (Short,1): Proj_UTM_zone_25N
> End_Of_Keys.
> End_Of_Geotiff.
>
> Why is ProjectedCSTypeGeoKey "User-Defined"?
> Why no linear units? I passed 'em, they were there in both the PROJ.4 string
> and the (converted from PROJ.4) WKT string!
> Why no GTCitationGeoKey?
> What's up with ProjectedCSTypeGeoKey and ProjectionGeoKey? Is GDAL confusing
> them?
Vladimir,
I was able to reproduce this with gdal_translate using:
gdal_translate -a_srs "+proj=utm +zone=11 +ellps=WGS84 +units=us-ft" in.tif out.tif
I fixed gt_wkt_srs.cpp so the units are written out, but the GEOGCS is still
not WGS84 since you have not set your datum to be WGS84 (just your ellipse).
I also get the right GEOGCS now if I use +datum=WGS84 instead of +ellps=WGS84.
Somewhat unrelated to your specific problem I also am not currently taking
any advantage of AUTHORITY[] information in my EPSG strings when writing out
GeoTIFF files. I will try to fix this tomorrow.
Best regards,
--
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I set the clouds in motion - turn up | Frank Warmerdam, warmerdam at pobox.com
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