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

[Jean-Claude Repetto]

On 01/17/11 18:40, Frank Warmerdam wrote:
>
> 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.

Frank, Even,

Thanks for the clarification. I have found that there are two different 
definitions of the Miller projection in use in PROJ.4 : esri:54003 which 
uses the authalic radius, and IGNF:MILLER, which uses the major axis.
There is probably no other solution than to use the +wktext parameter to 
differentiate both variants, so I won't file a ticket.

Regards,
Jean-Claude