Problem of Mercator Projection in OSM data


After I download OSM data from, I use the C# code here ( to transform the longitude and latitude into X and Y coordinates. Then I convert them into ArcGIS shapefile, and use the tool to calculate the area and length. To my big surprise, the results are not correct. For example, the actual area of Sweden is only 0.45 million square kilometers, while the result is summed to 1.17 million square kilometers.

Am I doing something wrong? Any of your response and comment are highly appreciated.




I am not sure about what projection the conversion formula yields but I suppose they are Mercator as the title suggests. Mercator projection does not suit at all for area measuments in high/low latitudes. Compare how Finland looks in and in

See how much the Google projection, which is a Mercator variant, is widening the northern part of Finland compared to more suitable UTM projection.

Take the Cloudmade shapefiles and convert them to some more suitable projection with some other tool, like ogr2ogr. For example UTM 33N will give better results

Ogr2ogr command to use is something like
ogr2ogr -f “ESRI Shapefile” -s_srs epsg:4326 -t_srs epsg:32633 Sweden_UTM.shp Sweden_WGS84.shp

Where “Sweden_UTM.shp” is the output file and “Sweden_WGS84.shp” is the input.