Preliminary results of lava flow mapping using remote sensing in Piton de la Fournaise, La Réunion island

The use of remote sensing is more and more incontrovertible in volcanic monitoring, especially in INSAR and thermal studies. A comprehensive database of high-resolution multispectral and multitemporal optical satellite imagery exists for Piton de la Fournaise, the active volcano on La Reunion Island. This database, however, remains relatively underexploited in volcanological studies of Piton de la Fournaise. Using a large image data set including SPOT 5 and 4, ASTER and aerial photography, we performed cartography of recent lava flows. Different methods were applied for each sensor in order to extract and map lava flow contours and surface morphology. These methods include photo interpretation as well as fusion of thermal band and optical images. In addition we performed several tests with specific software combining object and spectral based techniques. Subsequently, a simple statistical comparison between different perimeters and areas mapped allowed us to determine a precision ratio. Results show that difficulties in extracting contours arise when the study area is a complex lava flow field where the different lava flows overlap, or have a similar textural and radiometric characteristics.