5. Datum grids

Custom grid file should be required for shifting and transforming between datums. By default, CTS offers a list of the most common grid files (especially for the French area). These files are stored into a resource folder packaged with the CTS library. However, because of the size of some grid files, CTS uses also a local folder to store grids (.cts).

The principle is as follows :

If a grid is not available into the resource folder, then the library checks if it's in the .cts folder. If the .cts folder doesn't exit the program creates a new one. If the program can't find the desired grid it tries to download it on the grids folder repository available at https://github.com/orbisgis/cts/tree/master/grids