How to :: manage projections

What are projections ?

On a map, coordinates are generally expressed not as x and y as in a plan.

Instead, a latitude and a longitude are provided to denote that a location is a place on a sphere, rather than a plan.

Still, to represent this on a screen, which is a plan, we need to convert these into regular planar coordinates. That’s where a `projection <https://en.wikipedia.org/wiki/Map_projection>`__ comes in: a method to translate spherical coordinates into planar ones.

Many different projections exists, this part will explain how to configure them, under the key projection.

Default projection

By default, the Mercator projection (WGS 84) is assumed.

Warning

Tiles providers usually use this coordinate system. Changing to another would probably means breaking the tiles.

Planar coordinates

If geographical coordinates in your data are already projected on a plan, set projection to the value "plan".

This will use a simple cartesian projection.

Main use case for this is indoor maps.

Custom projection

Other projections are not supported for the moment, mainly because they would break tiles.

If your geographical data has been exported using another projection, please convert these the standard WGS 84 / EPSG 3857.

When importing a mesh file (BASEMAPS section in the etl_config.cson file), if the input projection is precised (mesh_projection), we handle this conversion automatically.