Hi Ulisse,
I don't think to a system that calculates the correction basing on the GPS coords, it would be too much work for the tiny TT processor.
Not really, there are pieces of code out there that can do it approximately, and fast, like "geoid.c" of the "gpsd"-package.
Have a look: http://www.sfr-fresh.com/linux/misc/gpsd-2.90.tar.gz:a/gpsd-2.90/geoid.c Best Regards and a Happy New Year! Stephan aka Joghurt
