[gdal-dev] gdaltransform and cs2cs don't agree ...

[Frank Warmerdam]

On 11-01-17 10:55 AM, Even Rouault wrote:
> I get the same results as in the cs2cs command line.
>
> I have no idea why we add +R_A when writting the PROJ.4 string of a Miller
> projection. SVN history points to a commit that dates back to 10 years ago :
> http://trac.osgeo.org/gdal/changeset/1862/trunk/ogr/ogr_srs_proj4.cpp
>
> Perhaps Frank will remember... ?
>
> In any case, you can open a Trac ticket to record the issue.

Even,

A bit of digging shows that +R_A tells PROJ.4 to use a spherical radius that
gives a sphere with the same surface area as the original ellipsoid.  I
imagine I added this while trying to get the results to match PCI's GCTP
based implementation though the history isn't clear on the details.

Likely I should not be inserting that though I'm not clear what radius
is chosen by default for spherical projections like this.  Certainly there
is no ambiguity if the coordinate system is actually using a sphere.

I'm not going to take any action without a ticket and I'm not absolutely
positive what I would do with one.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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and watch the world go round - Rush    | Geospatial Programmer for Rent