The bathymetry .dem raster data theme remains the same as in the prior image. Now we have loaded and overlain a .DRG USGS topo quad map in place of the USGS topo .dem file. The place to get these .DRG files in a readable format without having to pay USGS is at http://184.108.40.206/~mgreger/GIS/exchange.html – also known as the DRG data exchange. You can find your US quad and download it directly from here (coverage is very good – but some quads are missing – chances are good you will find yours). What you get is typically a GEOTIFF file (.tif), an accompanying world file for georeferencing (.tfw) and sometimes a metadata file. You need to unpack these files into the same folder cause .tif cannot be used by ARCVIEW unless it has a .tfw file with it.
GETTING DATA INTO ARCVIEW AND OVERLAYING
Make sure the TIFF extension is turned on under file – extensions. Then just go into your view with other themes and add a theme using the .tif file (make sure you specify that this is image data). Once again, go up to view – properties and make sure your projection is correct.