Wöppelmann, G. ; Gobron, K. ; de Viron, O. ; Poirier, E. ; Ballu, V. ; Van Camp, M.

Poster presented at AGU Fall Meeting 2019, San Francisco on 2019-12-13

Abstract: Since the use of the first tide poles for maritime navigation and tide prediction, sea level engineers have never stopped devising new technologies to provide more convenient and accurate ways to measure sea level. However, the operational use of newly developed technologies depends on their ability to provide accurate measurements in real conditions. To evaluate this ability, the sea level records of the new technologies are usually compared to that of a reference sensor, often using the so-called Van de Casteele test. If this type of buddy-checking method can provide an assessment of systematic biases, it can however not rigorously assess the precision (e.g., standard deviation of the sea level measurements from the new technology) because the random errors of the reference sensor also impact the differences. To address this metrological issue, we propose a new method for the cross-calibration of tide gauges. Based on the combination of at least three co-located sea level time series, it takes advantage of the Least-Squares Variance Component Estimation method to assess both sea-level biases and uncertainties in real conditions. The method was applied to a multi-instrument experiment carried out on Aix island, France, in 2016. Six water level gauges, including two GNSS buoys, were deployed to carry out simultaneous sea level recordings for 11 hours. We show that the proposed method allows assessing both the biases and the precision - i.e., the full accuracy - for each instrument. The results obtained with the proposed combination method have also been compared to that of a buddy-checking method. It showed that the combination of all time series also provides more precise bias estimates.

Keyword(s): Tide gauges ; Calibration ; Multi-instrument experiment ; Bias ; Aix Island, France