The EPSG Contract

Frank Warmerdam warmerdam at POBOX.COM
Tue Jan 10 14:40:33 EST 2006

On 1/7/06, Paul Ramsey <pramsey at> wrote:
> This implies, incidentally, some extra infrastructure at the backend,
> because the current Mapserver source of EPSG CRS information, the
> proj4 library, does not include ordinate order in its backend epsg
> database (the epsg file).  That leaves a pair of unpleasant
> implementation paths: add a whole new concept into proj4, and then
> have mapserver require the new library version in order to support
> WMS 1.3; or do a hack solution and simply assume all +proj=longlat
> combinations have reversed ordinates, unfortunately the hack will
> omit other cases, like several south african and some european
> projects, that also have a northing/easting order.


It is my intention to implement support for a +axis=...
option in PROJ.4 that can be used for switching the ordinates
and picking unusual axis directions (ie. south positive).  One
that is in place, there will still be challenges implementing
appropriate entries in the epsg translation table, but at least
there will be a coherant way of expressing alternate axis
orders without MapServer having to worry about it too much.

The WKT format already supports axis order/direction
definitions, though I have ignored in that in GDAL/OGR so far.

Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at
light and sound - activate the windows |
and watch the world go round - Rush    | Geospatial Programmer for Rent

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