8.17 Case Study No. 17Reference: Belsher, T. and M. Viollier, 1984,Thematic study of the 1982 SPOT simulation of Roscoff and the west coast of the Contentin peninsula (France). InProceedings of the Eighteenth International Symposium on remote sensing of environment, Paris, France. Ann Arbor, Environment Research Institute, pp. 1161–6Remote Sensing Technique: Airborne Remote Sensing:Platform - Aircraft (Simulated SPOT);Sensor - HRV.Objective: To give a quantitative evaluation of the seaweed cover and to determine the reliability of the technique for species differentiation.Experimental Rationale: The SPOT HRV (Haute Résolution Visible) sensor is primarily designed for land observation. Seaweed species in the intertidal zone, like land vegetation, may be classified according to their particular spectral reflectances. The spatial resolution of the HRV (20m) permits discrimination of relatively small seaweed patches.Method: The interval zone was initially isolated for analysis by the removal of water and land data from the imagery. Water has a very low reflectance in the near-infrared and the corresponding pixels are recognized by simple thresholding on channel 3 (790–890 nm). For land, interactive operations were required to superimpose the shoreline from accurate charts. A derived image was generated by computing a vegetation index Iv =
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