----------------------------Original message---------------------------- Hello A simple question - what is the formulae for transforming GPS coords to UK national Coords (via Lat and Long opresumably)? I'm not concerned about long base lines or plate tectonic movements (1-3cm changes in Europe per year) but do need to covert GPS 'centre of earth' coordinates back to UK (Transverse Mercator) national grid 6 figure references. Many thanks. John