[Mapserver-users] proj4 and mapserver

Frank Warmerdam warmerdam at pobox.com
Thu May 13 08:49:30 EDT 2004

Agneta Schick wrote:
> Dear reader,
> I'm trying to display a layer of symbols which are lat/long coordinates (from 
> shape files) on a map in winkel tripel projection (generated by GMT). 
> My problem is when I DO NOT specify "projection latlong" in the map file for 
> the layer with symbols, the symbols are displayed but, of course, in the
> wrong place and when I specify "projection latlong" the symbols are not 
> displayed at all. I assume that my specifications for the winkel tripel 
> projection are not correct/complete.
> Using "proj -l=wintri" I get
>    wintri : Winkel Tripel
>         Misc Sph
>         lat_1
> Does this mean that "lat_1" is the only information I need supply for the 
> projection definition aside from "proj=wintri"?


No, it just means that this is the only "special" parameter for this projection.
The listed information does not include the standard x_0, y_0, lat_0, and
lon_0 parameters.

> I've defined the map extents as -140 -90 220 90 with units dd. Can I use
> degrees when using proj4 although the output from proj is meters?

No.  Your basic problem would appear to be defining the map extents in
degrees but declaring the coordinate system to be winkel tripel.  I think
you will need to convert your extents to winkel tripel.

You should also supply an explicit ellipse for your winkel tripel
projection definition.

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

More information about the mapserver-users mailing list