On Fri, Feb 20, 2009 at 11:50:09AM +0100, Patrick O'Brian wrote: > Hi all, > > we are using google map layer with WMS from GeoServer using EPSG:23030. > We have detected a difference between geotools and OpenLayers srs > conversions using EPSG:900913 -> EPSG:23030. > Example: > 900913 => (-754113.99,4563131.15) > 23030_OpenLayers => (168035.13030878676,4199884.834826067) > 23030_GeoTools2.5.3 => (168141.88493782945,4199937.868013817) > > which is a huge difference: > dx=106.75462904269 m > dy=53.033187750 m > > The WMS image fits with google layer, but the cursor track shows a diferent > position than the database and the image with the geoserver preview. > > Can anyone tell us which is the correct srs conversion?
Not I, but this is one of two things: 1. a proj4js bug in porting proj 2. A disagreement in the meaning of the spatial reference. Looking at http://www.spatialreference.org/ref/epsg/23030/ , this is one of these ED50 projections I hear so much about: As I understand it, thre are multiple interpretations of ED50 projections depending on where you are. it seems that OpenLayers and GeoTools are making different default assumptions. I think the most likely solution here is that you will need to add a +towgs84 parameter to the proj4js string. It looks like the default for 23030 in GeoTools is: TOWGS84[-157.89, -17.16, -78.41, 2.118, 2.697, -1.434, -1.1097046576093785], So, if you take: Proj4js.defs["EPSG:23030"] = "+proj=utm +zone=30 +ellps=intl +units=m +no_defs"; And add +towgs84: Proj4js.defs["EPSG:23030"] = "+proj=utm +zone=30 +ellps=intl +units=m +togs84=-157.89,-17.16,-78.41,2.118,2.697,-1.434,-1.1097046576093785 +no_defs" The projection might work out better. CCing metacrs so that someone can tell me if I'm wrong here. Regards, -- Christopher Schmidt MetaCarta _______________________________________________ Dev mailing list Dev@openlayers.org http://openlayers.org/mailman/listinfo/dev
