  The vector map layers data, provided there, originated from Gazetteer of Planetary Nomenclature
of International Astronomical Union (IAU) Working Group for Planetary System Nomenclature (WGPSN),
which published on USGS site: http://planetarynames.wr.usgs.gov. The MERCURY_nomenclature.zip was 
used from the site, which contains shape-file representation.
  The datum presented here in form of .VML-files (stands Vector Map Layer), which is
proprietary compressed format of author of the datum.
  Additionally the datum contains data for Polar Regions of Mercury re-projected to Polar 
Stereographic projection. Areas of this re-projecting coincide with respective area for raster 
elevation data of MLA instrument of MESSENGER mission for North Polar Region and for both Polar 
Regions for areas of MDIS DEM data.

See site of author: www.runspect.com for more details.
Copyright (c) 2016 Yuri Feldman
