Coordinate systems

*Description in non-technical language

A coordinate system is an indication of how the location data of objects from the Earth’s surface (which is more or less a sphere) has been reproduced on a map (which is flat – both the paper one and the one on the screen)

There are several thousand coordinate systems:

  1. Some are adapted for the whole world (but are less accurate and maps can have distortions). For example, the so-called Web Mercator system (EPSG:3857)
  2. Others are for small areas but have very little distortion (e.g. the Polish series of layouts called PUWG 2000).

What needs to be remembered?

  1. It is not a big problem for modern GIS users.
  2. Every map (the one on the computer and the one on paper) has its own coordinate system.
  3. Spatial data stored in appropriate files (e.g. Shapefile or KML) has its own coordinate system (which system it is, you can check it e.g. in QGIS)
  4. The map on the computer may display in one coordinate system and the file may store data in another. During display, so-called on-the-fly reprojection takes place.
  5. Each layout has its own EPSG code so that they can be easily identified. List of ESPG codes

Read more:

Article on coordinate systems

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