GPS measurements of ocean loading and its impact on zenith tropospheric delay estimates: a case study in Brittany, France

• Published in: Journal of geodesy Vol. 76; no. 8; pp. 419 - 427
• Main Authors: VEY, S, CALAIS, E, HAASE, J. S, LLUBES, M, FLORSCH, N, WOPPELMANN, G, HINDERER, J, AMALVICT, M, LALANCETTE, M. F, SIMON, B, DUQUENNE, F
• Format: Journal Article
• Language: English
• Published: Berlin Springer 01.11.2002; Springer Verlag
• Subjects: Earth sciences; Earth, ocean, space; Exact sciences and technology; Internal geophysics; Marine; Solid-earth geophysics, tectonophysics, gravimetry; France; Brittany; Western Europe; ANE, France, Brittany; models; gravity field; maps; Europe; data processing; prediction; accuracy; troposphere; geodesy; Global Positioning System; Brittany; Western Europe; France
• ISSN: 0949-7714; 1432-1394
• DOI: 10.1007/s00190-002-0272-7

The results from a global positioning system (GPS) experiment carried out in Brittany, France, in October 1999, aimed at measuring crustal displacements caused by ocean loading and quantifying their effects on GPS-derived tropospheric delay estimates, are presented. The loading effect in the vertical and horizontal position time series is identified, however with significant disagreement in amplitude compared to ocean loading model predictions. It is shown that these amplitude misfits result from spatial tropospheric heterogeneities not accounted for in the data processing. The effect of ocean loading on GPS-derived zenith total delay (ZTD) estimates is investigated and a scaling factor of 4.4 between ZTD and station height for a 10 degree elevation cut-off angle is found (i.e. a 4.4-cm station height error would map into a 1-cm ZTD error). Consequently, unmodeled ocean loading effects map into significant errors in ZTD estimates and ocean loading modeling must be properly implemented when estimating ZTD parameters from GPS data for meteorological applications. Ocean loading effects must be known with an accuracy of better than 3 cm in order to meet the accuracy requirements of meteorological and climatological applications of GPS-derived precipitable water vapor.