Projection problems with Google maps / Virtual Earth I don't really understand whats happening here - so would be grateful for any suggestions. I have 2 .map files serving out WMS data: - BNG.map - WGS84.map
Both these map files are displaying the same data - but one has the raw data as British National Grid (epsg 27700) and the other as WGS84 (epsf 4326) When tested in a client such as MapInfo - alignment is exact for both However when displayed on virtual earth / google maps (using the projection <54004> +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0+y_0=35 +k= 1.0 +units=m +no_defs <>) if using the WMS service from the WGS84.map file - alignment is fine if using the WMS service from the BNG.map file - the overlay is about 100m off to NW What I don't understand is why these both work fine in a client such as MapInfo, but only one fails in Virtual Earth / Google maps - as one works presumably I've got this working OK ? The difference is both that when being called from MapInfo the request uses SRS=27700 so no conversion is required It seems as if the conversion from 27700 to 54004 is messing up - but 4326 to 54004 works OK ? OK - looked a bit deeper in MapInfo - and if I change the WMS request from the BNG.map file to return data as SRS=4326 (as in the query below) - I get similar miss alignment GET /scripts/mapserv.exe?map=C:/Inetpub/wwwroot/MapserverService/Map/WMSTest.map&LAYERS=OSBUILD&VERSION= 1.1.1&REQUEST=GetMap&LAYERS=OSBUILD&STYLES=&SRS=EPSG:4326&BBOX=-3.296092, 51.945322,- 3.290018, 51.949813&WIDTH=971&HEIGHT=718&FORMAT=image/png&TRANSPARENT=TRUE&BGCOLOR=0xFFFFFF&EXCEPTIONS=application/vnd.ogc.se_xmlHTTP/1.1 I don't remeber having these issues when using mapserver via CGI - it only seems to relate to WMS Obviously I can convert all my data to WGS84 and avoid the problem - but thats not an ideal long term solution Any ideas Thanks James
