.477 File Extension
What is an .477 file?
.477 is MNS Shape Definition Companion File
File used by Master Navigation Software, a GIS navigation program used on laptops and mobile devices; saved with a corresponding ESRI shapefile (.SHP extension) and contains the the type definition for the PROJ.4 cartographic projection data.
477 files are used for accurately placing geographic boundaries and other map features on a rendered map.