National transformation (NTv2) for Proj.NET.
A concatenated transform of two projected coordinate systems
[0] Source CS (PROJ) -> Source CS (GEOG)
[1] Source CS (GEOG) -> Target CS (GEOG)
[2] Target CS (GEOG) -> Target CS (PROJ)
gets replaced with
[0] Source CS (PROJ) -> Source CS (GEOG)
[1] Source CS (GEOG) -> Grid Transformation -> Target CS (GEOG)
[2] Target CS (GEOG) -> Target CS (PROJ)
A concatenated transform of two geographic coordinate systems
[0] Source CS (GEOG) -> Source CS (GEOC)
[1] Source CS (GEOC) -> Target CS (GEOG)
gets replaced with
[0] Source CS (GEOG) -> Grid Transformation -> Target CS (GEOG)
The library was tested only with German grid file BETA2007.gsb from http://www.crs-geo.eu/BeTA2007 which converts Gauss-Krueger to ETRS89 / UTM.