seamlessly join USGS DRG (.tif) using world file (.tfw)

Here's an open source, command line tool "quadjoin" to seamlessly join
1 or more USGS DRG (.tif) files using the accompanying world file
(.tfw file) Any collars are clipped. Note: the tiff files must have
the same attributes, e.g. scale, color map, etc. Along with the source
there are executables for linux (Fedora) and XP (using cygwin).

More information and a map of a section of appalachian trail at:
http://quadjoin.sourceforge.net/

Frank Glandorf
Cincinnati, USA