Commercial GPS in the Stratosphere: Cell Phone GPS Receiver Performance on a High Altitude Weather Balloon

Jonathan Carroll, Bryan Chan, Charles Harner, Tyler Reid, Paul Tarantino, Chi Yau Tony Yu

Abstract:	The primary objective of this effort was to characterize the GPS performance of a smartphone at high altitudes. Due to International Traffic in Arms Regulations (ITAR) restrictions in the United States, very little GPS data above 60,000 ft (18.3 km) is openly available. Tethered to a high altitude weather balloon, a Google Nexus S cell phone was taken to high altitudes while logging GPS data. It successfully recorded GPS navigation data throughout the majority of the flight including above the 60,000 ft threshold as it ascended to a peak altitude of 102,300 ft (31.2 km). Design decisions, trade studies, and system testing of the balloon mission were undertaken in the months leading up to flight. Throughout its flight, the cell phone logged many parameters including altitude, position, positional accuracy, and velocity in the WGS-84 Geoid surface plane. Analysis of the payload’s positional accuracy related to the horizontal speed, altitude, and vertical speed was performed on both the ascent and descent profiles. Examination of this data revealed a gap in the data shortly after the balloon burst during freefall. For a comparison baseline, a mathematical model was developed to predict the payload’s altitude and vertical speed during descent. Contrasting this model with the GPS data during descent showed that the GPS position fix was first lost and then regained at a vertical speed of around 25 m/s. The large vertical velocity was postulated to be the main driver in the positional accuracy error since there was no noticeable trend between positional accuracy and altitude or horizontal speed.
Published in:	Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011) September 20 - 23, 2011 Oregon Convention Center, Portland, Oregon Portland, OR
Pages:	3245 - 3254
Cite this article:	Carroll, Jonathan, Chan, Bryan, Harner, Charles, Reid, Tyler, Tarantino, Paul, Yu, Chi Yau Tony, "Commercial GPS in the Stratosphere: Cell Phone GPS Receiver Performance on a High Altitude Weather Balloon," Proceedings of the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2011), Portland, OR, September 2011, pp. 3245-3254.
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