int. j. remote sensing, 2002, vol. 23, no. 7, 1461–1474 Mapping tropical coastal vegetation using JERS-1 and ERS-1 radar data with a decision tree classier M. SIMARD*†, G. DE GRANDI‡, S. SAATCHI† and P. MAYAUX‡ †Jet Propulsion Laboratory, MS 300–227, 4800 Oak Grove Drive, Pasadena, CA 91109, USA ‡Space Application Institute of the European Commission Joint Research Centre, Ispra (VA), Italy Abstract. The objective of this paper is to investigate the complementarity of JERS-1 and ERS-1 data for mapping coastal tropical regions. We use a decision tree classier to classify a coastal region of Gabon and describe the feature contribution using the decision tree diagram. The JERS-1 Global Rain Forest Mapping (GRFM) and ERS-1 Central Africa Mosaic Project (CAMP) datasets are used. The result is a land cover map of the west coast of Gabon. The analysis explicitly shows the complementary characteristics of the L- and C-band Synthetic Aperture Radar (SAR) instruments. We demonstrate the usefulness of combined use of L- and C-band data for large area mapping of coastal regions, especially in ooded areas for discrimination of high and low mangroves as well as grasses and tree swamps. The overall classication accuracy increases by 18% over single band classication. 1. Introduction The objective of this paper is to investigate the complementarity of ERS-1 and JERS-1 Synthetic Aperture Radar (SAR) data for mapping of coastal tropical regions. We use SAR image mosaics constructed in the frame of two continental-scale radar mapping projects: the ERS-1 TREES CAMP (Central Africa Mosaic Project) (Malingreau and Duchossois 1995, De Grandi et al. 1999) and JERS-1 GRFM (Global Rain Forest Mapping) (Rosenqvist 1996, De Grandi et al. 2000a). The former is a European Commission project executed at the Joint Research Centre (JRC). The latter was initiated by NASDA (National Space Development Agency of Japan) and the JRC (Joint Research Center), Jet Propulsion Laboratory and NASA Alaska SAR Facility acted as the main processing nodes. We focus our study on a coastal area of Gabon. In moist tropical forest regions, the quasi-permanent cloud cover does not allow for on-demand optical data acquisition of land cover. Thus, in these regions radar data becomes invaluable for mapping land cover (Nezry et al. 1993, Luckman et al. 1997), hydrography and oods (Ford and Casey 1988, Hess et al. 1990, 1995, Kux et al. 1993, Kasischke et al. 1997). Even if ERS-1 (CVV, C-band vertical polarization) and JERS-1 (LHH, L-band horizontal polarization) are expected to individually provide poor information on tropical forest vegetation species (Kasischke et al. 1997, *e-mail: simard@innu.jpl.nasa.gov International Journal of Remote Sensing ISSN 0143-1161 print/ISSN 1366-5901 online © 2002 Taylor & Francis Ltd http://www.tandf.co.uk/journals DOI: 10.1080 /01431160110092984