SWATH MAPPING SYSTEM PROCESSING - BATHYMETRY AND CARTOGRAPHY

During swath mapping cruises various geophysical data were collected. Bathymetry, imagery and other geophysical information require speciali sed post-processing. Dedicated software enables post-processing and vi sualisation of each type of data. A graphic interface collects the fil es and exports them to a CAD system for cleaning and for adding extra information. The huge amount of soundings from multibeam echo sounder systems and the very particular sampling along and across the ship's t rack demand powerful software such as TRISMUS provides. Major steps in the processing are the merging of raw soundings with navigation corre cted if necessary, the cleaning of soundings with a bandpass filter an d the gridding of the data to obtain a Digital Terrain Model. Despite care and real time filtering during the acquisition phase, some errors persist and appear as abnormal patterns on contoured maps. It is ofte n difficult to distinguish the origins of the errors and consequently to correct them in a deterministic way. But the analysis and descripti on of typical patterns allows errors to be classified into five groups - sounding, profile, overlap area, surveyed area or gridding artefact - and in some cases to adopt specific processing techniques to reduce or cancel undesirable effects. Merging bathymetric maps and sonar mos aics can be achieved with IMAGEM or with the high level graphic interf ace MFEDIT. Since dedicated software splits the information up into di fferent layers, the operator can manage the layers according to the in formation he wants on the final document. Additional information such as seismic reflection data and interpretation, geological logs and leg ends, can be imported or created as extra layers.