[Lonesome in Massachussets]

It was a little hand held GPS unit for use by private pilots in unpressurized cabins. It incorporated a barometric altimeter, and the capability for the pilot to input a local reference altitude to account for variations in surface air pressure. Normally pilots can adjust their cabin altimeters to indicated the known altitude of the runway before take off to account for changes in local barometric pressure. Airliners are pressurized to about 8000 ft., which means that when you are flying at 30,000 feet a barometric altimeter inside the cabin with you will indicate 8000 ft.

[U S Army EOD]

My Garmin 96C works just great using the satellites.

[zipper]

It was a little hand held GPS unit for use by private pilots in unpressurized cabins

Yes, redundantly. Light aircraft already have an altimeter.

[ColdWater]

It was a little hand held GPS unit for use by private pilots in unpressurized cabins.

Probably a GPS NOT designed for pilots.