Hi Anne, check the example (first couple of lines in comments):
http://trac.openlayers.org/browser/trunk/openlayers/examples/web-mercator.js?rev=10384 So that's up to the application to provide (at least for now). But I can also see that's not really easy for end-users. What do other people think about providing the EPSG aliases by default in the OL library? Best regards, Bart > Hello Bart, > > I am not sure if > > http://trac.openlayers.org/ticket/2665 > > takes care of the side effect that Control.Measure and MousePosition are > no longer working properly after resetting the projection code? > > Anne > > On 7/19/2010 12:29 PM, Bart van den Eijnden (OSGIS) wrote: >> Hi Anne, >> >> in trunk this has been addressed, see: >> >> http://trac.openlayers.org/ticket/2665 >> >> Best regards, >> Bart >> >>> Hello list, >>> >>> OpenStreetMap and also some popular commercial mapservices (google, >>> bing, yahoo) are using the so called sphericalmercator projection. >>> OpenLayers has built-in support for this type of layer, inherited from >>> OpenLayers.Layer.SphericalMercator. >>> >>> If you use a sphericalmercator layer as a baselayer, you may want to >>> combine this with other layers. By default, the openlayers >>> sphericalmercator baselayer uses SRS projection-code 'EPSG:900913' . >>> So, >>> if you try to open an overlay, the overlay layer will be called with >>> parameter SRS=EPSG:900913. >>> >>> EPSG Code 900913 happens to be a bogus code, based on the word >>> 'google'. >>> Perhaps due to the resemblance of '900913' and 'google' or due to other >>> reasons, there are now several other codes in use for the same >>> projection: >>> EPSG:3857 >>> EPSG:3785<= maybe because of a typo by someone somewhere? >>> EPSG:102113 >>> >>> Some map-services have stopped supporting SRS=EPSG:900913 and this >>> raises a problem for openlayers sphericalmercator users. Instead of >>> displaying a map, these mapservices will respond with something like >>> 'no >>> support for EPSG:900913'. >>> >>> The problem of overlaying sphericalmercator layers that do not support >>> epsg:900913 can be (partly) solved as follows: >>> Override the default srs code for sphericalmercator layers by >>> explicitly >>> resetting the projection before adding the layer to a map: >>> >>> var osmLayer = new OpenLayers.Layer.OSM("OpenStreetMap"); // osmlayer >>> is >>> now sphericalmercator with default epsg:900913 >>> osmLayer.projection = new OpenLayers.Projection ("EPSG:3857"); // >>> osmlayer is now sphericalmercator with epsg:3857 >>> map.addLayers ([osmLayer]); >>> >>> Overlay layers will now be requested with SRS=ESPG:3857 >>> >>> However, resetting the code for the baselayer projection, causes >>> trouble >>> for the controls for MousePosition and MeasureControl: distances and >>> coordinates are no longer presented in the correct projection. >>> >>> I solved this by adding the following lines of code to file >>> lib\OpenLayers\Layer\SphericalMercator.js >>> OpenLayers.Projection.addTransform("EPSG:4326", "EPSG:3857", >>> OpenLayers.Layer.SphericalMercator.projectForward); >>> OpenLayers.Projection.addTransform("EPSG:4326", "EPSG:102113", >>> OpenLayers.Layer.SphericalMercator.projectForward); >>> OpenLayers.Projection.addTransform("EPSG:4326", "EPSG:3785", >>> OpenLayers.Layer.SphericalMercator.projectForward); >>> >>> OpenLayers.Projection.addTransform("EPSG:3857", "EPSG:4326", >>> OpenLayers.Layer.SphericalMercator.projectInverse); >>> OpenLayers.Projection.addTransform("EPSG:102113", "EPSG:4326", >>> OpenLayers.Layer.SphericalMercator.projectInverse); >>> OpenLayers.Projection.addTransform("EPSG:3785", "EPSG:4326", >>> OpenLayers.Layer.SphericalMercator.projectInverse); >>> >>> Questions: >>> - is this the way to support aliases for 900913 and support >>> MousePosition and MeasureControl at the same time? >>> - if yes, shouldn't the above lines be part of the standard OpenLayers >>> distribution? >>> >>> Anne Blankert >>> >>> >>> _______________________________________________ >>> Users mailing list >>> [email protected] >>> http://openlayers.org/mailman/listinfo/users >>> >> > > > > -- Looking for flexible support on OpenLayers or GeoExt? Please check out http://www.osgis.nl/support.html Bart van den Eijnden OSGIS [email protected] _______________________________________________ Users mailing list [email protected] http://openlayers.org/mailman/listinfo/users
