Context and objectives
Bathymetrical surveys of an extended area of the sea bottom using conventional methods are complex, very expensive, and are characterised by an intrinsic inaccuracy due to non-simultaneous collection of data. The inaccuracy is amplified by the fast and intense changes of the sea bottom and by difficulties in radio-positioning at sea.
Satellite remote sensing has the advantage of providing synoptic data on a regular basis. The possibility of recurrent acquisitions allows study of the morphological evolution of the sea bottom, which is very important in the context of the evaluation of the stability of marine constructions.
Purpose of the study : research how the sea bottom topography can be determined on the basis of indirect observations such as the modulation of sea currents and swell of sea water, which are visible on satellite images.
Expected scientific results
- Contrasts in the sea due to gradation in depth and suspended elements can be easily observed on the SPOT XS3 band.
- The LANDSAT TM image could not be used due to the occurrence of ‘striping’ (horizontal lines). It was not possible to correct the image with the ERDAS ‘destripe’ function nor by a customised programme.
- The hydrodynamic and meteorological conditions at the time of the image acquisition determine the usefulness of ERS-1 SAR satellite images for mapping the sea bottom : some structures of the sea bottom can only be perceived if the tidal currents are parallel to the structures, …
- It is recommended to know the characterisation (volume and type) of the suspended and dissolved elements in the sea when using a SPOT image.
- Classification in depth of the sea bottom based on a SPOT image approximates reality better than a classification on the basis of ERS-1 SAR images.
- The classification of SPOT as well as ERS-1 SAR is mainly interesting for the identification of structures with a high depth gradient.
- The synergy of both images is not clear.
|Project leader(s):||ULg - Laboratoire de Géomorphologie et Télédétection|