Tag Archives: datum

“Web mercator” coordinate system: explained!

I’ve spent quite a lot of time trying to understand the differences between the several flavours of the “web mercator” coordinate system used by many web-based mapping systems to store and present their data. Various names, various EPSG codes, various definitions and various conversions are all in use. So I was pleased to come across this detailed explanation. It’s not a quick read, but it does make sense of a fraught field – thank you to Alastair Aitchison.