DESCRIPTION
This command is undocumented upstream. This very rough documentation was quickly assembled by your friendly Debian maintainer (who doesn't use this command, and so is not the best person to document it!).
The proj package includes the nad2nad binary, the North American Datum conversion filter used to convert data between North America Datum 1927 (NAD27) and North American Datum 1983, and cs2cs a binary that performs transformation between the source and destination cartographic coordinate system on a set of input points. The coordinate system transformation can include translation between projected and geographic coordinates as well as the application of datum shifts.
See the nad2nad(1) and cs2cs(1) man pages for more information.
nad2nad and cs2cs need arch-dependent conversion data files in a library directory, /usr/share/proj/ Those files are included in the proj Debian package since 4.6.1-5. To produce/update them yourself, get the *.lla files from
http://download.osgeo.org/proj/proj-datumgrid-1.5.zip
and then run nad2bin to produce the binary files used by nad2nad and cs2cs like so:
# nad2bin < conus.lla /usr/share/proj/conus
Test nad2nad with the following example:
$ nad2nad -i 83 -o 27 -r conus << EOF
71d14'58.27"W 44d20'15.227"N
EOF
It should produce:
71d15'W 44d20'15"N