2:15 PM - 2:30 PM
[G06-5-04] Observation of sea surface heights from moving ships based on analysis of GNSS-SNR data
Current studies investigate the possibilities to combine satellite altimetry and tide gauge readings with GNSS-based observations from moving ships to derive precise information of the sea surface height (SSH). The latter method requires determining the variable distance between the GNSS antenna and the undisturbed water surface. Commonly the distance is calculated based on hydrostatic and hydrodynamic data. Since some of the necessary corrections are not always available or not easy to derive (draft changes due to fuel consumption or ship squat), it would be desirable to connect the GNSS antenna and the sea surface by direct and continuous observations.
It is well-know that GNSS-SNR data can be utilized to derive water surface heights. Up to now, existing inversion techniques were only used for the analysis of SNR observations from static GNSS antennas. If these techniques could be applied also to observations from moving ships, the resulting reflector height could be used together with GNSS -derived antenna heights to directly observe the ellipsoidal height of the water surface around the ship without the need of dynamic corrections.
To assure that the used SNR observations are not influenced by the wave system of the ship only data from low elevation angles should be analysed. The movements of the ship can be calculated from the observations of at least three GNSS antennas aboard the ship and will be used to correct for the short-periodic variations of reflector heights in the inversion step. Hence, the static reflector height together with a long-term variation due to draft change and squat effect can be modelled as 2D time depending function.
The inversion of the SNR data is carried out by global optimization based on interval analysis. This method will be applied to a data set from a ship cruise in the North Sea. The results from this experiment will be presented and future applications will be discussed.
It is well-know that GNSS-SNR data can be utilized to derive water surface heights. Up to now, existing inversion techniques were only used for the analysis of SNR observations from static GNSS antennas. If these techniques could be applied also to observations from moving ships, the resulting reflector height could be used together with GNSS -derived antenna heights to directly observe the ellipsoidal height of the water surface around the ship without the need of dynamic corrections.
To assure that the used SNR observations are not influenced by the wave system of the ship only data from low elevation angles should be analysed. The movements of the ship can be calculated from the observations of at least three GNSS antennas aboard the ship and will be used to correct for the short-periodic variations of reflector heights in the inversion step. Hence, the static reflector height together with a long-term variation due to draft change and squat effect can be modelled as 2D time depending function.
The inversion of the SNR data is carried out by global optimization based on interval analysis. This method will be applied to a data set from a ship cruise in the North Sea. The results from this experiment will be presented and future applications will be discussed.