Disclaimer: I'm very new to GIS. I want to calculate the areas of school districts in Nevada (and California at some point) using census shape files. http://www.census.gov/geo/cob/bdy/sn/sn00shp/sn32_d00_shp.zip
The data is unprojected so I know I must project it onto something good for equal areas. I'm trying NAD83 California Albers (SRID = 3310). It seems to me from reading the documentation and numerous other posts/tutorials, that the following code should return the area of the districts in meters (or something I can convert to meters). select area(transform(the_geom, 3310)) from mytable This returns a column of areas which match my unprojected areas exactly! I've fiddled with setting the constraint to SRID=3310, importing through the qGIS SPIT plugin, selecting into a new table, delete and resetting constraints, and on and on... FWIW, I can load the file into qGIS, set the projection to 3310, and the identify area feature calculates the "derived area" exactly as it should be. I can't for the life of me figure out how to even get into the approximately correct units. (I've tried reprojecting to quite different SRIDs and can see the area change slightly, but it still appears to be in native map units or degrees). Thanks for any assistance, Charles _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
