Transverse Mercator Projection

Newbie question: Is OSM based on Transverse Mercator Projection? If not, then what?

AFAIK, the OSM main edit database uses the only reasonable coordinate system for a globe spanning dataset like OSM’s, that is, a geographic (non-projected) WGS1984 coordinate system. Actually, since it is not a true spatial database using the spatial extension of PostgreSQL (PostGIS), it just stores the X/Y coordinates based on WGS1984 in a relational schema, so it most probably doesn’t actually inherently define the geographic WGS1984 coordinate system as the coordinate system for storage, as you would have to do for a true spatial database.

Most rendering databases use WGS1984 Web Mercator Auxiliary Sphere projection.

Ah. That makes sense of course. Many thanks for the fast response. Couldn’t see anywhere what the underlying system was, being a newbie.

However, if I wanted to see on screen (and work with it) an OSM map of, say, Italy, with a Lambert Conical Orthographic projection (and all that it implies with regards to distances in any direction from a given point), how, if at all possible, could I do that?

You can do this using a GIS (geographical information system) SW like QGIS which is free

Many thanks for that tip Beerforfree. Looks very promising for my project of putting WWII military-grid maps online. My specialist area is Special Forces operations in the Mediterranean Theatre, and I’m wrestling with the difficulty of easily translating War Diary Grid Refs into actual locations.