AN INDEPENDENT FEASIBILITY ASSESSMENT OF VERIPOS GNSS BASED TIDAL HEIGHTING AGAINST POLPRED TIDAL PREDICTIONS DURING A ROUTE SURVEY IN THE SOUTHERN NORTH SEA

A feasibility study of using Veripos Ultra GNSS service for real time tidal observations and analysis is presented. Veripos Ultra provides several positioning services for hydrographic applications. The Ultra correction is a precise point positioning (PPP) method to achieve vertical accuracy between 10-15 centimetres. The use of real time observations offers benefits such as removing the need of pressure gauges, accounting for atmospheric effects on sea level and the use of tide prediction software. This thesis evaluates the performance of the Veripos Ultra Tides system as a tool of measuring real time tides against Polpred, a tide prediction software. Veripos data was logged during the mobilisation of the vessel and a route survey carried out by N-Sea Survey B.V. With the water level data recorded during the mobilisation, a static tidal analysis was carried out to compare the performance of the Veripos Tides and Polpred against the local port tide gauge. The static tide analysis carried out at Ijmuiden port showed the Veripos had an accuracy of ±24cm relative to the tide gauge data, while Polpred showed an accuracy of ±62cm. The bathymetric data recorded during the route was duplicated and processed in QINSy using Veripos and Polpred tide data. The results showed that using real time observations for tidal correction produced smaller vertical uncertainties between overlapping bathymetric files than using predicted data. All the results are presented as a case study in the southern part of the North Sea by this paper