<p><br>Projection problems with Google maps / Virtual Earth<br>I don't really understand whats happening here - so would be grateful for any suggestions.<br>I have 2 .map files serving out WMS data:<br> - BNG.map<br> -
WGS84.map<br> <br>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)<br>When tested in a client such as MapInfo - alignment is exact for both
<br>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 <>)<br>if using the WMS service from the
WGS84.map file - alignment is fine<br>if using the WMS service from the BNG.map file - the overlay is about 100m off to NW<br>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 ?
<br>The difference is both that when being called from MapInfo the request uses SRS=27700 so no conversion is required<br>It seems as if the conversion from 27700 to 54004 is messing up - but 4326 to 54004 works OK ?<br>
<br>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<br> <br>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_xml
HTTP/1.1<br> <br>I don't remeber having these issues when using mapserver via CGI - it only seems to relate to WMS<br> <br>Obviously I can convert all my data to WGS84 and avoid the problem - but thats not an ideal long term solution
<br> <br>Any ideas</p>
<p>Thanks<br>James</p>