I'm developing an application for Android that one of the purposes is to measure variation of elevation (altitudes). I am aware that today we are unable to get altitude data with high accuracy (even medium i guess). I stared to search alternatives, and I know that there are Global Elevation Data that I could probably use to my calculations (by the way - can you recommend some good data provider as I need this in offline mode on the device so it would be nice if I could download it in file and use inside app).
If GPS altitude doesn't work properly if you are trying to check it inside the building, I want to make sure that if you are on a dry ski slope - will it be incorrect too ?