fixed USGS-DEM reader detection of non-USGS files
fixed USGS-DEM reader detection of non-USGS files

seanisom/vtp,markraz/vtp,nakijun/vtp,nakijun/vtp,nakijun/vtp,seanisom/vtp,seanisom/vtp,seanisom/vtp,markraz/vtp,nakijun/vtp,seanisom/vtp,markraz/vtp,markraz/vtp,nakijun/vtp,markraz/vtp