Hello List, I am amazed by Openlayers' capabilities of displaying Google Maps, VE and WMS/WFS layers all on the same map.
So it did not bother me much when I noticed that Google and VE have an approx. 50 meter displacement (in my part of the world, NE of Rome, Italy). When I looked closer at google I noticed that the matching between the imagery and the road layer was pretty bad it made me feel better. When I added my own cadastral data I got worried. There is about 100m vertical displacement between my data and V.E. data. Now VE are using the same ortophotos I am using (50cm pixel aerial imagery made by the most respectable company in Italy - indisputably perfect). These ortophotos are provided by the company in the projection of "Gauss Boaga" (which ESRI wrongly call Monte Mario - Italy). What's more the Road layer in VE matches the ortophotos perfectly. The road layer (Teleatlas / Navteq) comes in UTM - WGS84 and I also combine it with my cadastral data. I play with these projections every day and are very confident with them - but not so with the so called "spherical mercator" Does anybody have any opinion in the matter ? has anyone tried to overlay Google / VE / Yahoo with very accurate maps ? For the record I am doing the following: (maybe something wrong) projections in Proj.4 epsg file: # Spherical Mercator for Google etc. <900913> +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m [EMAIL PROTECTED] +no_defs # GAUSS BOAGA EST <3004> +proj=tmerc +lat_0=0 +lon_0=15.0 +k=0.999600 +x_0=2520000 +y_0=0 +ellps=intl +pm=0 +units=m no_defs <> I define my map thus: var smproj = new OpenLayers.Projection("EPSG:900913"); mapOptions = { projection: smproj, units: "m", displayProjection: geoproj }; my layers thus: var hyblayer = new OpenLayers.Layer.VirtualEarth( .... 'sphericalMercator': true}); var pmwms = new OpenLayers.Layer.WMS( ..... {'projection': smproj}); -- View this message in context: http://www.nabble.com/Conversion-to-Spherical-Mercator---100m-error-tp18898188p18898188.html Sent from the OpenLayers Users mailing list archive at Nabble.com. _______________________________________________ Users mailing list Users@openlayers.org http://openlayers.org/mailman/listinfo/users