The links on http://joe.mehaffey.com/transformation.htm may prove useful
to you. Note that there are two issues to deal with: grid conversion
(which is the one you asked about) and datum conversion (which you may
not be aware of). GPS units output positions based on the WGS-84 (World
Geodetic Survey 1984) datum; Irish ordnance survey maps are based on the
Ireland 1965 datum. In Ireland there is a difference of around 100
metres between the two - I learned this the hard way!
A piece of shareware which I use and have quite a lot of respect for is
at http://www.gpsu.co.uk - this will talk to GPS units, display routes
and waypoints overlaid on maps if you so desire, and perform grid and
datum conversions on position data. Unfortunately this software is
currently Windows only but the author intends to port it to Linux now
that Kylix is available.
Christian J van den Bosch mailto:cjb at linux.ie
"To err is human - to moo, bovine"
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