**6. Acknowledgements**

These reasearch were financed by the "Region Reunion" and the ministry of "l'Enseignement Supérieur et de la Recherche" program. The authors would like to thank the CNES (Centre National d'Etudes Spatial) for the free access to the SPOT data via the KALIDEOS program (http://kalideos.cnes.fr).

This piece of work also used free ASTER data obtained thanks to AIST GEO Grid (Ministry of Economy, Trade and Industry) programm.

Thanks to Rebecca Roger for the translation.
