THE DATA
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://216.36.33.21/~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.