Remote Sensing Techniques for Mangrove Mapping Chaichoke Vaiphasa Promotors: Prof. Dr. A.K. Skidmore Professor of Vegetation and Agricultural Land Use Survey International Institute for Geo-information Science and Earth Observation (ITC), Enschede and Wageningen University, the Netherlands Prof. Dr. H.H.T. Prins Professor of Tropical Nature Conservation and Vertebrate Ecology Wageningen University, the Netherlands Co-promotor: Dr. W.F. de Boer Assistant Professor Resource Ecology Group Wageningen University, the Netherlands Examining Committee: Prof. Dr. M.E. Schaepman Wageningen University Wageningen Prof. Dr. S.M. de Jong Utrecht University Utrecht Dr. Itthi Trisirisatayawong Chulalongkorn University Bangkok, Thailand Prof. Dr. A.M. Cleef University of Amsterdam Amsterdam Remote Sensing Techniques for Mangrove Mapping Chaichoke Vaiphasa Thesis To fulfil the requirements for the degree of Doctor on the authority of the Rector Magnificus of Wageningen University, Prof. Dr. M.J. Kropff, to be publicly defended on Tuesday 31 January, 2006 at 15:00 hrs in the auditorium of ITC, Enschede, The Netherlands. ISBN: 90-8504-353-0 ITC Dissertation Number: 129 International Institute for Geo-information Science & Earth Observation, Enschede, The Netherlands © 2006 Chaichoke Vaiphasa Table of Contents Table of Contents........................................................................................i Abstract......................................................................................................v Samenvatting ............................................................................................vi Acknowledgements................................................................................. vii Chapter 1 General Introduction ................................................................1 1.1 Remote sensing for mangrove studies .......................................3 1.2 Hyperspectral remote sensing for mangrove discrimination .....3 1.3 Burdens of hyperspectral data ...................................................5 1.3.1 Dimensionality problems...................................................5 1.3.2 Noise levels........................................................................7 1.4 Utilizing mangrove-environment relationships .........................8 1.5. Objectives of the study ..............................................................9 1.6. Outline of the thesis.................................................................10 Chapter 2 Hyperspectral Data for Mangrove Discrimination.................13 Abstract....................................................................................................14 2.1 Introduction..............................................................................15 2.2 Methods ...................................................................................17 2.2.1 Acquisition of hyperspectral data ....................................17 2.2.1.1 Mangrove leaf preparation...............................................17 2.2.1.2 Leaf spectral measurements.............................................19 2.2.2 Data treatments ................................................................20 2.2.2.1 Statistical test...................................................................20 2.2.2.2 Spectral separability.........................................................21 2.3 Results......................................................................................23 2.3.1 ANOVA test....................................................................23 2.3.2 Wrapper feature selection ................................................24 2.3.3 J-M distance.....................................................................24 2.4 Discussion & conclusion.........................................................27 Chapter 3 Dimensionality Problems.......................................................29 Abstract....................................................................................................30 3.1 Introduction..............................................................................31 3.2 Data & Methods.......................................................................32 3.2.1 Species-level hyperspectral data......................................32 3.2.1.1 Mangrove leaf preparation...............................................32 3.2.1.2 Leaf spectral measurements.............................................33 3.2.2 Genetic search algorithms (GA) ......................................34 3.2.2.1 Gene encoding .................................................................34 i 3.2.2.2 Reproduction mechanism ................................................35 3.2.2.3 Fitness criterion ...............................................................36 3.3 Experiments & Results ............................................................36 3.3.1 Initialising the genetic search algorithm..........................36 3.3.2 Choosing an appropriate chromosome size .....................36 3.3.3 Running the genetic search algorithm .............................37 3.3.4 Testing the key hypothesis...............................................42 3.4 Discussion & Conclusion........................................................43 Chapter 4 Spectral Smoothing................................................................47 Abstract....................................................................................................48 4.1 Introduction..............................................................................49 4.2 Methods ...................................................................................51 4.2.1 Smoothing techniques......................................................51 4.2.1.1 Moving average ...............................................................52 4.2.1.2 Savitzky-Golay ................................................................52 4.2.2 Hyperspectral data collection ..........................................52 4.2.3 Experimental use of smoothing filters.............................54 4.2.3.1 Statistical comparisons ....................................................54 4.2.3.2 Spectral separability analysis...........................................54 4.3 Results......................................................................................55 4.4 Discussion & Conclusion........................................................59 Chapter 5 Ecological Data Integration ...................................................63 Abstract....................................................................................................64 5.1 Introduction..............................................................................65 5.2 Methods ...................................................................................66 5.2.1 Study site.........................................................................66 5.2.2 Field survey.....................................................................68 5.2.2.1 Ecological data collection................................................68 5.2.2.2 Mangrove sampling .........................................................70 5.2.3 Input data for the post-classifier ......................................71 5.2.3.1 Soil pH interpolation........................................................71 5.2.3.2 Plant-environment relationships ......................................72 5.2.3.3 The classified image ........................................................73 5.2.4 The post-classifier............................................................76 5.2.5 Statistical test...................................................................77 5.3 Results......................................................................................78 5.4 Discussion & conclusion.........................................................79 Chapter 6 The Synthesis .........................................................................81 6.1 Introduction..............................................................................83 6.2 The main results.......................................................................84 ii 6.2.1 Hyperspectral data for mangrove discrimination.............84 6.2.3 Noise levels......................................................................89 6.2.4 Utilizing mangrove-environment relationships ...............91 6.3 This thesis in a nutshell! ..........................................................92 6.3.1 Why is the follow-on research needed?...........................93 6.3.2 Be at ease with hyperspectral data...................................93 6.3.3 Is exploiting non-spectral information promising?..........95 6.4 Conclusion ...............................................................................96 References................................................................................................97 Curriculum vitae ....................................................................................115 Author’s bibliography............................................................................116 Appendix I: Genetic algorithms step by step.........................................117 Appendix II: Spectral signatures of the mangroves...............................121 Appendix III: The variogram of soil pH interpolation ..........................122 ITC Dissertation List .............................................................................123 iii iv Abstract Mangroves, important components of the