README

Lanelet2 Projection Module

This module implements different projection functions as required by lanelet2_io.

Need for projections

As map data is commonly stored in WGS84 (lat/lon/ele) and lanelet2 operates on metrical data, there is a need for precise projection functions between the two. There are very good projection functions available, but they have to be used with the correct origin (close to the location of the map).

Maps loaded with a wrong origin can easily be distorted by 40% and more. Angle calculations will be wrong as well.

For more details, read here.

Supported Projections

  • UTM.h: WGS84 (for storage in .osm files) <-> UTM (internal processing) (wrapper of https://sourceforge.net/projects/geographiclib/). This projection has the advantage of being very precise, but all points in the map must fit into one UTM Tile. If points exceed a 100 km margin, the map can not be loaded.

  • Mercator.h: WGS84 (for storage in .osm files) <-> Local Mercator as in liblanelet. Approximates the earth

  • Geocentric.h: WGS84 <-> ECEF (wrapper of https://sourceforge.net/projects/geographiclib/).

  • LocalCartesian.h: WGS84 <-> LocalCartesian (wrapper of https://sourceforge.net/projects/geographiclib/). This is similar to UTM; however, it properly treats elevation.