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PostGIS Essentials by Angel Marquez

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What is a spatial reference system?

We could think about Earth as a perfect sphere that will float forever in space and never change its shape, but it is not. Earth is alive and in a state of constant change, and it's certainly not a perfect circle; it is more like an ellipse (though not a perfect ellipse) with a lot of small variations, which have taken place over the years.

If we want to represent a specific position inside this irregular shape called Earth, we must first make some abstractions:

  1. First we have to choose a method to represent Earth's surface into a regular form (such as a sphere, ellipsoid, and so on).
  2. After this, we must take this abstract three-dimensional form and represent it into a two-dimensional plane. This process is commonly ...

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