Flight Testing and Data Analysis of Airborne GPS LADS Survey

Shaowei Han, Chris Rizos, Ralph Abbot

Abstract:	An experiment was conducted in December 1997 to test the utility of the kinematic GPS technique to determine aircraft height to high accuracy, over very long baselines, in support of the Royal Australian Navy’s Laser Airborne Depth Sounder (LADS) system. The LADS survey area was located over Torres Strait, north of Cape York, between Australia and Papua New Guinea. The primary reference station was located at Cairns Airport where the LADS F27 aircraft was based, about 900 km south of the survey area. A secondary reference station was located on Thursday Island in the Torres Strait, about 100 km south of the survey area. An additional aim of the experiment was to assess the suitability of the Ashtech Z12, Leica MC1000 and NovAtel Millennium receivers for this application. All three receiver types were installed in the aircraft and fed by the same antenna using a signal splitter. The Cairns reference station employed both a Leica and a NovAtel receiver, whilst the Thursday Island station used both an Ashtech and a Novatel receiver. In a single flight sortie, LADS travelled from Cairns to the survey area, where it remained on-station for 2.5 hours, collecting swaths of water depth data before returning to Cairns. In this paper the data analysis procedure which has been developed to evaluate GPS receiver performance is described, and some results of long range, carrier phase-based GPS kinematic positioning are presented. The GPS receiver performance evaluation is based on a number of factors, including the data logging quality, multipath rejection ability and the noise level of measurements. The aircraft trajectory, and especially the height component, which is essential in this application, was derived using the "ambiguity recovery" technique. Based on the above analysis, it could be concluded that GPS is able to deliver sub-decimetre level positioning accuracy with output data rates of between 4Hz and 10Hz.
Published in:	Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998) September 15 - 18, 1998 Nashville, TN
Pages:	1211 - 1221
Cite this article:	Han, Shaowei, Rizos, Chris, Abbot, Ralph, "Flight Testing and Data Analysis of Airborne GPS LADS Survey," Proceedings of the 11th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 1998), Nashville, TN, September 1998, pp. 1211-1221.
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