There is only one file type that uses the .NETSPM extension:
NetSpot Map File
File created by NetSpot, a program used for surveying wireless networks; stores a map on which a wireless network heatmap can be overlaid; often contains building floorplans or property land surveys.
NetSpot maps can be created from several standard image and page layout formats, including .JPG, .GIF, .TIF, and .PDF.
Updated: December 19, 2011