GPS receivers calculate position in 3 dimensions, although they're not very good at altitude calculation. I knew that, and I checked the manual for my 910 and then Googled it to see if there was any built in capability. I found a hack that's supposed to install it in a x00 model, at this guy's site:
http://www.ilpiola.it/roberto/tomtom/
So I downloaded it and installed it in the 910. It froze, unresponsive to shutoff and touchscreen but thankfully not to the USB connection to my Mac. It took maybe 10 resets and two restores before it would act normally.
So I'll wait for him to work it out for the x10 models before I try it again. He admitted it's not too accurate, not like, say, an etrex with built-in aneroid barometer.
But if a braver soul makes it work in a new TT, maybe they'll post the how-to here.
http://www.ilpiola.it/roberto/tomtom/
So I downloaded it and installed it in the 910. It froze, unresponsive to shutoff and touchscreen but thankfully not to the USB connection to my Mac. It took maybe 10 resets and two restores before it would act normally.
So I'll wait for him to work it out for the x10 models before I try it again. He admitted it's not too accurate, not like, say, an etrex with built-in aneroid barometer.
But if a braver soul makes it work in a new TT, maybe they'll post the how-to here.