UNCORRECTED PROOF ARTICLE IN PRESS 1 Multi-site evaluation of IKONOS data for classification of 2 tropical coral reef environments 3 Serge Andre ´foue ¨t a, * , Philip Kramer b , Damaris Torres-Pulliza c , Karen E. Joyce d , 4 Eric J. Hochberg e , Rodrigo Garza-Pe ´rez f , Peter J. Mumby g , Bernhard Riegl h , 5 Hiroya Yamano i , William H. White j , Mayalen Zubia k , John C. Brock c , 6 Stuart R. Phinn d , Abdulla Naseer l , Bruce G. Hatcher l , Frank E. Muller-Karger a 7 a Institute for Marine Remote Sensing, College of Marine Science, University of South Florida, 140 7th Avenue S., St. Petersburg, FL 33701, USA 8 b Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL, USA 9 c Center for Coastal and Regional Marine Studies, United States Geological Survey, St. Petersburg, FL, USA 10 d Biophysical Remote Sensing Group, Department of Geographical Sciences and Planning, University of Queensland, St. Lucia, Australia 11 e Hawaii Institute of Marine Biology, University of Hawaii, Honolulu, Kaneohe, USA 12 f Coral Reef Ecosystems Ecology Laboratory, Marine Resources Department, CINVESTAV-I.P.N. Unidad Me ´rida, Merida, Mexico 13 g Marine Spatial Ecology Laboratory, University of Exeter, Exeter, UK 14 h Oceanographic Center, National Coral Reef Institute, Nova Southeastern University, Miami, FL, USA 15 i Social and Environmental Systems Division, National Institute for Environmental Studies, Onogawa, Tsukuba, Ibaraki, Japan 16 j Department of Marine Science and Coastal Management, The University of Newcastle, Newcastle upon Tyne, UK 17 k Laboratoire Terre-Oce ´ans, Universite ´ de la Polyne ´sie Francaise, Tahiti, French Polynesia 18 l Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada 19 20 Received 3 June 2002; received in revised form 5 December 2002; accepted 22 April 2003 21 Abstract 22 Ten IKONOS images of different coral reef sites distributed around the world were processed to assess the potential of 4-m resolution 23 multispectral data for coral reef habitat mapping. Complexity of reef environments, established by field observation, ranged from 3 to 15 24 classes of benthic habitats containing various combinations of sediments, carbonate pavement, seagrass, algae, and corals in different 25 geomorphologic zones (forereef, lagoon, patch reef, reef flats). Processing included corrections for sea surface roughness and bathymetry, 26 unsupervised or supervised classification, and accuracy assessment based on ground-truth data. IKONOS classification results were 27 compared with classified Landsat 7 imagery for simple to moderate complexity of reef habitats (5 – 11 classes). For both sensors, overall 28 accuracies of the classifications show a general linear trend of decreasing accuracy with increasing habitat complexity. The IKONOS sensor 29 performed better, with a 15– 20% improvement in accuracy compared to Landsat. For IKONOS, overall accuracy was 77% for 4 – 5 classes, 30 71% for 7 – 8 classes, 65% in 9– 11 classes, and 53% for more than 13 classes. The Landsat classification accuracy was systematically lower, 31 with an average of 56% for 5 –10 classes. Within this general trend, inter-site comparisons and specificities demonstrate the benefits of 32 different approaches. Pre-segmentation of the different geomorphologic zones and depth correction provided different advantages in different 33 environments. Our results help guide scientists and managers in applying IKONOS-class data for coral reef mapping applications. 34 D 2003 Elsevier Inc. All rights reserved. 35 36 Keywords: Landsat; Bathymetric correction; Glint; Accuracy; Habitat mapping; Seagrass 37 38 39 1. Introduction 40 Remote sensing provides an effective way to observe 41 and monitor shallow coral reefs worldwide, to characterize 42 inter-reef structural differences, and to map intra-reef 43 habitat diversity and zonations, assess bathymetric varia- 44 tions, design survey protocols, conduct biogeochemical 45 budgets, and map beta-diversity (Andre ´foue ¨t, Claereboudt, 46 Matsakis, Page `s, & Dufour, 2001; Andre ´foue ¨t, Muller- 47 Karger, Hochberg, Hu, & Carder, 2001; Andre ´foue ¨t & 48 Payri, 2000; Capolsini, Andre ´foue ¨t, Rion, & Payri, 2003; 49 Hochberg & Atkinson, 2000; Jupp et al., 1985; Liceaga- 0034-4257/$ - see front matter D 2003 Elsevier Inc. All rights reserved. doi:10.1016/j.rse.2003.04.005 * Corresponding author. Tel.: +1-727-553-3987; fax: +1-727-553-1103. E-mail address: serge@seas.marine.usf.edu (S. Andre ´foue ¨t). www.elsevier.com/locate/rse RSE-05965 Remote Sensing of Environment xx (2003) xxx – xxx