Determination of geoid height at Breid Bay, east Antarctica

Abstract

By the combined observation of satellite Doppler positioning, Global Positioning System (GPS) relative carrier phase measurement, and ocean tide observation, we obtained the geoid height at Breid Bay (70°12′S, 23°47′E) as 16.8 m above the World Geodetic System 1984 (WGS84) Earth ellipsoid. The broadcast ephemeris satellite Doppler positioning was made, and the ellipsoidal height at L0 point on the ice sheet of Breid Bay is estimated to an accuracy of ±4 m from the accepted 95 Navy Navigation Satellite System (NNSS) satellite passes. GPS relative carrier phase measurement was made between L0 point and the deck of the icebreaker Shirase (S point). The height difference between L0 point and S point is determined to an accuracy of ±0.3 m from the analysis of 15‐min carrier phase data from four satellites by the doubly differenced phase method. The recording of sea level variation was made using the sea bottom pressure‐transducer water level recorder for 4 days, together with monitoring of ship's attitude and meteorological data. The separation of S point from the local mean sea level is determined to an accuracy of ±0.3 m. The standard deviation of the obtained geoid height can be considered to be (42 + 0.32 + 0.32)½ ∼ 4 m. Thus obtained geoid height at S point is 3.4 m smaller than the WGS84 model geoid (18 order truncation) and 8 m smaller than the OSU‐86D geoid of 250 order harmonics. Though the discrepancy of a few meters may be explained by local geoid highs in Breid Bay, 3–5 m systematic depression of geoidal contours may be required in the region concerned (20°E to 40°E) in order to explain geoid heights at both S point and Syowa Station. The method we applied here is operationally simple and appropriate for dense installation of geoid height control stations along circum‐Antarctic coastal zone.