Travis Kirstine writes: > > We have been developing a web mapping application using google maps as > the front end interface with a postgis backend. Using this > application the user can draw a bounding box in google maps and the > coordinates are then passed to postgis. With postgis we then perform > a query on the polygons stored in the postgis database to return the > area using ST_Intersection, ST_Transform (usually to UTM) and finally > ST_Area. The application works great but the problem is that since > we are trying to work on a global scale it is difficult to determine > what projection (EPSG) to transform the data to calculate an accurate > area since our data is in EPSG:4326 and returns decimal degrees. We > can easily transform the query results to a UTM or a Albers projection > however the results can be inaccurate since the user may select > multiple zones or hemispheres when view the map at a global scale. Is > there a accurate global projection for calculating area?
This paper discusses the problem and describes its solution in a non FOSS system http://geodyssey.com/papers/ggelare.html I see this but haven't read it http://portal.acm.org/citation.cfm?id=302304.302315 HTH Norman _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users
