I've been playing around with an Arduino and the SparkFun GPS shield. For about a week, it was working well, but it has now developed an interesting error.
While my latitude, longitude, date, time and course are correct, the GPS is telling me that it is 10 000 000 m above sea level. Previously, it was giving readings between 90 and 110 m, which would be correct for my local area.
I have tried everything I can think of to fix the problem; reinstalling the libraries and using a couple of different sketches off the internet, but they all have the same problem.
I'm not sure if the GPS module has gone bad because all other outputs are working, but this being my first GPS project I'm not 100% on how it determines altitude figures. I am willing to pay another $80 to get a new module but I'd rather not if it's not the problem.