Application of the dual-CGPS concept to monitoring vertical land movements at tide gauges

Abstract

Recently the concept of using dual-continuous GPS (dual-CGPS) stations for monitoring vertical land movements at tide gauge sites was proposed by a working group of the European Sea Level Observing System (EOSS). In this concept, one CGPS station is established at the tide gauge, in order to monitor the local vertical land movements, and a second CGPS station is established on stable rock, within a few kilometers of the tide gauge further inland. Since 1997, a network of CGPS stations has been established to monitor vertical land movements in the UK. For the dual-CGPS station concept, pairs formed by the CGPS stations at Newlyn tide gauge and Camborne and at Lowestoft tide gauge and Hemsby, have been analyzed over a time span of approximately 2.7 and 2.0 years respectively. It has been shown by numerous authors that temporal and spatial correlations in CGPS coordinate time series can introduce biases in the estimated station velocities and their uncertainties. By analyzing the coordinate time series of two CGPS stations close to each other, spatial correlations can be removed successfully by differencing and a cleaner, difference time series for each coordinate component can be obtained. In this paper, the observed coordinate time series of four CGPS stations have been used to produce synthetic coordinate time series of 6 years in length. Station velocities and their uncertainties have been derived for both observed and synthetic coordinate time series and compared in order to assess the capabilities of the dual-CGPS concept to better describe local and geophysical vertical land movements.