1. Space representation

1.1 Coordinate systems

Mastering coordinate systems is fundamental, as the slightest error can have a significant impact on the location and management of georeferenced data.

When using GNSS systems (global navigation satellite systems), reference points are global on an Earth scale. They are based on geodetic reference systems defined by :

• a Cartesian geodetic reference frame attached to the globe;

• a flattened ellipsoid of revolution modelling the globe;

• a system of coordinates and units.

The geodesic reference frame has its origin close to the Earth's center of mass, a z-axis close to the pole axis, an x-axis that passes close...