[ryandrake]

That would depend on what your resolution and accuracy requirements are. Ground level or treetop? If you are willing to DIY there are freely available DEM (Digital Elevation Model) datasets that might work for you. For example ASTER[1] has global 90 meter resolution and 30 meter resolution in the USA. There are smaller, embeddable DEMs with ~1km resolution. Lots of options out there. Grab a coffee and start with an internet search for DEM.

1: https://en.m.wikipedia.org/wiki/Advanced_Spaceborne_Thermal_...

[BattyMilk]

Cheers, I'll take a read. I'm looking for ground level (I use it to calibrate the barometer on my watch at the start of a hike/trail run/climb)