Let's see how the projection we used since the beginning of the book works. It is the EPSG:4326, or Plate Carrée (flat square), which is a coordinate system with an equirectangular projection using the WGS84 (World Geodesic System 1984) ellipsoid.
We need a mathematical model to begin with, as the real shape of Earth is uneven, and therefore, very hard to represent mathematically. The most simple shape we can model Earth with is a sphere. As there is a great difference between the real size of Earth and the optimal sphere that it can be represented with, we can use a little more complex shape to increase overall accuracy--an ellipsoid. As Earth is a little flattened on the poles, an ellipsoid (technically an ...
