Originally Posted by
cyccommute
A Google search of accuracy of the two measurements give a raw error of 10m to 20 m for GPS (35 to 70 feet) while barometers are accurate to ±15 meters.
An accuracy of ±15 meters seems too high to me for a barometric pressure sensor.
Garmin reports ±10 feet accuracy for their barometric altimeter (exclusive of barometric drift).