Here is a list of all documented modules with brief descriptions:

Nfortranc	Utility module for supporting Fortran 2003 C language interface module
Ngdal	Fortran 2003 interface to the gdal http://www.gdal.org/ library
Nproj	Fortran 2003 interface to the proj.4 https://github.com/OSGeo/proj.4 library
Nreadosm	Fortran 2003 interface to the readosm https://www.gaia-gis.it/fossil/readosm/index library
Nshapelib	Fortran 2003 interface to the shapelib http://shapelib.maptools.org/ library