AN ASSESSMENT OF VIDEO-BASED BATHYMETRY ESTIMATION IN A MACRO TIDAL ENVIRONMENT

Abstract

This paper investigates the utility of video systems for estimating coastal bathymetry in a highly energetic and strongly macro-tidal environment using a linear wave theory inversion approach (cBathy). cBathy has been improved recently (Holman, et al. 2013), introducing a non-linear fit procedure of a phase structure over an area around a point of interest and a Kalman filter. cBathy has been extensively tested in micro/meso tidal environments but never in a macro tidal environment. Now the model is put to the test for the first time in these tidal conditions at Porthtowan, Cornwall in the United Kingdom. The combination of the macro-tidal range and energetic waves means that the accuracy of cBathy is compromised. A novel solution for macro tidal areas is presented in this paper where the pixels lose their fixed position and float around based on the corresponding tidal elevation. cBathy and the modified code are subsequently compared to topographical RTK-GPS measurements covering the inter-tidal area during spring tide. Depending on the tide and waves, the accuracy of the depth estimates varies, but during spring tide (6-7 metre tidal range) the results with the tidal correction are improved significantly. A reduction in RMS-error of 25% for the inter-tidal zone can be found in the most extreme cases.