Can recreational echosounderchartplotter systems

Authors: J Horta A Pacheco D Moura Ó Ferreira

Publish Date: 2014/10/09

Volume: 64, Issue: 11, Pages: 1555-1567

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Abstract

This work intends to determine if lowcost surveying techniques based on recreational echosounders can be used to perform nearshore bathymetry for analysing evolution of coastal sectors For that purpose two hydrographic surveying techniques were compared ie 1 a realtime kinematic differential global positioning system RTKDGPS synchronised with a single beam echosounder with realtime tidal elevation correction and 2 a lowcost recreational echosounderchartplotter system using Global Navigation Satellite Systems GNSS with realtime European Geostationary Navigation Overlay Service EGNOS augmentation services and depth values postprocessed using measured sea level Two bathymetric data sets were obtained one by each method for the same area and survey lines at an ebb tidal delta Tavira Inlet Ria Formosa Portugal Vertical differences were determined assuming no morphological variations between surveys Results showed that depth elevation differences between bathymetric surfaces were of 010 ± 016 m slightly higher but within the same order of the error attributable to the used interpolator 000 ± 011 m triangular surface fitting The differences between surveys performed with two different equipment sets and using different methodologies for correcting water elevations are very small both quantitative and qualitatively Those differences can be diminished by improving the tidal level correction and uncertainties associated to different tidal slopes throughout the survey area Pitch/roll corrections performed with lowcost GPS receivers would be also a valuable addition to the accuracy and precision of the method It is then concluded that navigation with EGNOS augmentation services and sounding devices ten times cheaper than combined RTKDGPS with single beam echosounders allow to measure and monitor accurately the nearshore bathymetryThis paper is a contribution to the project EROS – Erosion of Rocky Shores – differences in protection promoted by sandy beaches and shore platforms FCT–PTDC/CTEGIX/111230/2009 and project MOSES Moving Sands Equilibrium State of Crenulated Coasts PTDC/GEOGEO/3981/2012 funded by the Portuguese Foundation for Science and Technology André Pacheco was supported Portuguese Foundation for Science and Technology grant number SFRH/BPD/76110/2011 The authors would like to acknowledge the contribution of João SalvéRainha for logistical support during data acquisition We also greatly acknowledge the contribution of the reviewers that greatly contributed to improve early versions of this work particularly to Edwin Danson

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