[Geotiff] Linear Units of Projections Parameters

[David Burken]

All:

Here is an example of the problem Frank is talking about:

The geotiff file is keyed as such:

ProjLinearUnitsGeoKey (Short,1): Linear_Foot
ProjFalseEastingGeoKey (Double,1): 400000

So is the false easting 400,000 meters or 400,000 feet?

Snip from the spec:
ProjLinearUnitsGeoKey = 3076 /* Section 6.3.1.3 
<http://www.remotesensing.org/geotiff/spec/geotiff6.html#6.3.1.3> codes
ProjFalseEastingGeoKey = 3082 /* ProjLinearUnits */

Frank Warmerdam wrote:

> Folks,
>
> What are peoples opinions on how the units of linear quantities
> like false easting and northing should be interpreted in a GeoTIFF file?
>
> Reviewing the specification (ie. the definition of ProjFalseEastingGeoKey
> in 2.7.2 of the specification) it seems clear that the false easting and
> northing should be in the units defined by ProjLinearGeoKey.
>
> But listgeo's normalized parameter report, GDAL, and a variety of other
> commercial software packages all seem to make the assumption that false
> easting and northing are always in meters.
>
> I have created a bug report against the specification about this 
> topic, though
> it may just be that libgeotiff, GDAL and various other packages need 
> to be
> fixed.  I am worried if alot of packages get it wrong, and no one gets it
> right (other than OSSIM so far) that we might cause more problems by 
> changing
> the common convention.
>
>   http://bugzilla.remotesensing.org/show_bug.cgi?id=1094
>
> Best regards,

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