Friday 22 March 2019

coordinate system - What's the difference between EPSG:4326 and EPSG:900913?


I am a bit confused on EPSG:4326 and EPSG:900913. I thought that they were both same. Though as I am placing my features over GMaps, which is EPSG:4326, I need to define the srsname of the WFS layer as EPSG:900913 to get it into the right place. If I define srsname as 4326 it is projected somewhere completely wrong.


Could someone explain it a bit more in detail as to what is wrong here?



Answer



They are not the same. EPSG:4326 refers to WGS 84 whereas EPSG:900913 refers to WGS84 Web Mercator. EPSG:4326 treats the earth as an ellipsoid while EPSG:900913 treats it as a sphere. This affects calculations done based on treating the map as a flat plane which is why your features got plotted on the wrong places.


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