{String} Set in the map options to specify the default projection for layers added to this map.  When using a projection other than EPSG:4326 (CRS:84, Geographic) or EPSG:3857 (EPSG:900913, Web Mercator), also set maxExtent, maxResolution or resolutions.  Default is “EPSG:4326”.  Note that the projection of the map is usually determined by that of the current baseLayer (see baseLayer and getProjectionObject).

{OpenLayers.Projection} Requires proj4js support for projections other than EPSG:4326 or EPSG:900913/EPSG:3857.  Projection used by several controls to display data to user.  If this property is set, it will be set on any control which has a null displayProjection property at the time the control is added to the map.

1. //坐标转换  
2. function corTransform(lon, lat) {  
3.     var proj = new OpenLayers.Projection("EPSG:4326");  
4.     var lonlat = new OpenLayers.LonLat(lon, lat);  
5.     lonlat.transform(proj, this.map.getProjectionObject());  
6.     return lonlat;  
7.   
8. }  

1. /** 
2.  * APIMethod: transform 
3.  * Transform the LonLat object from source to dest. This transformation is 
4.  *    *in place*: if you want a *new* lonlat, use .clone() first. 
5.  * 
6.  * Parameters: 
7.  * source - {<OpenLayers.Projection>} Source projection. 
8.  * dest   - {<OpenLayers.Projection>} Destination projection. 
9.  * 
10.  * Returns: 
11.  * {<OpenLayers.LonLat>} Itself, for use in chaining operations. 
12.  */  
13. transform : function (source , dest) {  
14.     var point = OpenLayers.Projection.transform(  
15.         {‘x‘ : this.lon , ‘y‘ : this.lat} , source , dest);  
16.     this.lon = point.x;  
17.     this.lat = point.y;  
18.     return this;  
19. } ,