Remote Sensing with Imaging Radar (eBook)

John A. Richards (Autor)

eBook Download: PDF

2009 | 1. Auflage
XIX, 361 Seiten
Springer-Verlag
978-3-642-02020-9 (ISBN)

Infos

This book is concerned with remote sensing based on the technology of imaging radar. It assumes no prior knowledge of radar on the part of the reader, commencing with a treatment of the essential concepts of microwave imaging and progressing through to the development of multipolarisation and interferometric radar, modes which underpin contemporary applications of the technology. The use of radar for imaging the earth's surface and its resources is not recent. Aircraft-based microwave systems were operating in the 1960s, ahead of optical systems that image in the visible and infrared regions of the spectrum. Optical remote sensing was given a strong impetus with the launch of the first of the Landsat series of satellites in the mid 1970s. Although the Seasat satellite launched in the same era (1978) carried an imaging radar, it operated only for about 12 months and there were not nearly so many microwave systems as optical platforms in service during the 1980s. As a result, the remote sensing community globally tended to develop strongly around optical imaging until Shuttle missions in the early to mid 1980s and free-flying imaging radar satellites in the early to mid 1990s became available, along with several sophisticated aircraft platforms. Since then, and particularly with the unique capabilities and flexibility of imaging radar, there has been an enormous surge of interest in microwave imaging technology. Unlike optical imaging, understanding the theoretical underpinnings of imaging radar can be challenging, particularly when new to the field.

Inhalt

Preface 6
TABLE OF CONTENTS 8
LIST OF SYMBOLS AND OPERATORS 13
Operators and mathematical conventions 19
CHAPTER 1 THE IMAGING RADAR SYSTEM 20
1.1 Why Microwaves? 20
1.2 Imaging with Microwaves 20
1.3 Components of an Imaging Radar System 22
1.4 Assumed Knowledge 24
1.4.1 Complex Numbers 25
1.4.2 Vectors and Matrices 25
1.4.3 Differential Calculus 25
1.5 Referencing and Footnotes 25
1.6 A Critical Bibliography 25
1.7 How this Book is Organised 28
CHAPTER 2 THE RADIATION FRAMEWORK 30
2.1 Energy Sources in Remote Sensing 30
2.2 Wavelength Ranges used in Remote Sensing 33
2.3 Total Available Energy 34
2.4 Energy Available for Microwave Imaging 36
2.5 Passive Microwave Remote Sensing 38
2.6 The Atmosphere at Microwave Frequencies 38
2.7 The Benefits of Radar Remote Sensing 40
2.8 Looking at the Underlying Electromagnetic Fields 41
2.9 The Concept of Near and Far Fields 45
2.10 Polarisation 47
2.11 The Jones Vector 52
2.12 Circular Polarisation as a Basis Vector System 55
2.13 The Stokes Parameters, the Stokes Vector and the Modified Stokes Vector 57
2.14 Unpolarised and Partially Polarised Radiation 59
2.15 The Poincaré Sphere 61
2.16 Transmitting and Receiving Polarised Radiation 63
2.17 Interference 67
2.18 The Doppler Effect 68
CHAPTER 3 THE TECHNOLOGY OF RADAR IMAGING 72
PART A: THE SYSTEM 72
3.1 Radar as a Remote Sensing Technology 72
3.2 Range Resolution 74
3.3 Pulse Compression Radar 77
3.4 Resolution in the Along Track Direction 80
3.5 Synthetic Aperture Radar (SAR) 80
3.6 The Mathematical Basis for SAR 81
3.7 Swath Width and Bounds on Pulse Repetition Frequency 85
3.8 The Radar Resolution Cell 87
3.9 ScanSAR 87
3.10 Squint and the Spotlight Operating Mode 90
PART B: THE TARGET 94
3.11 The Radar Equation 94
3.12 Theoretical Expression for Radar Cross Section 96
3.13 The Radar Cross Section in dB 96
3.14 Distributed Targets 97
3.15 The Scattering Coefficient in dB 98
3.16 Polarisation Dependence of the Scattering Coefficient 99
3.17 The Scattering Matrix 100
3.18 Target Vectors 104
3.19 The Covariance and Coherency Matrices 105
3.20 Measuring the Scattering Matrix 108
3.21 Relating the Scattering Matrix to the Stokes Vector 109
3.22 Polarisation Synthesis 111
3.23 Compact Polarimetry 122
3.24 Faraday Rotation 125
CHAPTER 4 CORRECTING AND CALIBRATING RADAR IMAGERY 128
4.1 Sources of Geometric Distortion 128
4.1.1 Near Range Compressional Distortion 128
4.1.2 Layover, Relief Displacement, Foreshortening and Shadowing 130
4.1.3 Slant Range Imagery 132
4.2 Geometric Correction of Radar Imagery 134
4.2.1 Regions of Low Relief 134
4.2.2 Passive Radar Calibrators 135
4.2.3 Active Radar Calibrators (ARCs) 136
4.2.4 Polarimetric Active Radar Calibrators (PARCs) 137
4.2.5 Regions of High Relief 137
4.3 Radiometric Correction of Radar Imagery 139
4.3.1 Speckle 139
4.3.2 Radar Image Products 146
4.3.3 Speckle Filtering 147
4.3.4 Antenna Induced Radiometric Distortion 152
CHAPTER 5 SCATTERING FROM EARTH SURFACE FEATURES 154
5.1 Introduction 154
5.2 Common Scattering Mechanisms 154
5.3 Surface Scattering 155
5.3.1 Smooth Surfaces 155
5.3.2 Rough Surfaces 158
5.3.3 Penetration into Surface Materials 167
5.4 Volume Scattering 172
5.4.1 Modelling Volume Scattering 172
5.4.2 Depolarisation in Volume Scattering 177
5.4.3 Extinction in Volume Scattering 178
5.5 Scattering from Hard Targets 179
5.5.1 Facet Scattering 180
5.5.2 Dihedral Corner Reflector Behaviour 181
5.5.3 Metallic and Resonant Elements 186
5.5.4 Bragg Scattering 189
5.5.5 The Cardinal Effect 190
5.6 Composite Scatterers 191
5.7 Sea Surface Scattering 191
5.8 Internal (Ocean) Waves 197
5.9 Sea Ice Scattering 197
CHAPTER 6 INTERFEROMETRIC AND TOMOGRAPHIC SAR 200
6.1 Introduction 200
6.2 The Importance of Phase 200
6.3 A Radar Interferometer - InSAR 202
6.4 Creating the Interferometric Image 204
6.5 Correcting for Flat Earth Phase Variations 205
6.6 The Problem with Phase Angle 206
6.7 Phase Unwrapping 208
6.8 An Inclined Baseline 209
6.9 Standard and Ping Pong Modes of Operation 210
6.10 Types of SAR Interferometry 211
6.11 The Concept of Critical Baseline 213
6.12 Decorrelation 215
6.13 Detecting Topographic Change: Along Track Interferometry 217
6.14 Polarimetric Interferometric SAR (PolInSAR) 221
6.14.1 Fundamental Concepts 221
6.14.2 The T6 Coherency Matrix 225
6.14.3 Maximising Coherence 226
6.14.4 The Plot of Complex Coherence 227
6.15 Tomographic SAR 228
6.15.1 The Aperture Synthesis Approach 228
6.15.2 The Fourier Transformation Approach to Vertical Resolution 234
6.15.3 Unevenly Spaced Flight Lines 235
6.15.4 Polarisation in Tomography. 236
6.15.5 Polarisation Coherence Tomography 236
6.16 Range Spectral Filtering and a Re-examination of the Critical Baseline 248
CHAPTER 7 BISTATIC SAR 251
7.1 Introduction 251
7.2 Generalised Radar Networks 252
7.3 Analysis of Bistatic Radar 254
7.3.1 The Bistatic Radar Range Equation and the Bistatic Radar Cross Section 254
7.3.2 Bistatic Ground Range Resolution 255
7.3.3 Bistatic Azimuth Resolution 260
7.4 The General Bistatic Configuration 267
7.5 Other Bistatic Configurations 274
7.6 The Need for Transmitter-Receiver Synchronisation 275
7.7 Using Transmitters of Opportunity 276
7.8 Geometric Distortion and Shadowing with Bistatic Radar 277
7.9 Remote Sensing Benefits of Bistatic Radar 278
7.10 Bistatic Scattering 279
CHAPTER 8 RADAR IMAGE INTERPRETATION 282
8.1 Introduction 282
8.2 Analytical Complexity 282
8.3 Visual Interpretation Through an Understanding of Scattering Behaviours 283
8.3.1 The Role of Incidence Angle 284
8.3.2 The Role of Wavelength 285
8.3.3 The Role of Polarisation 286
8.4 Quantitative Analysis of Radar Image Data for Thematic Mapping 288
8.4.1 Overview of Methods 288
8.4.2 Features Available for Radar Quantitative Analysis 290
8.4.3 Application of Standard Classification Techniques 291
8.4.4 Classification Based on Radar Image Statistics 292
8.4.4.1 A Maximum Likelihood Approach 292
8.4.4.2 Handling Multi-look Data 295
8.4.4.3 Relating the Scattering and Covariance Matrices, and the Stokes ScatteringOperator 296
8.4.4.4 Adding Other Dimensionality 297
8.5 Interpretation Based on Structural Models 298
8.5.1 Interpretation Using Polarisation Phase Difference 298
8.5.2 Interpretation Through Structural Decomposition 300
8.5.2.1 Decomposing the Scattering Matrix 301
8.5.2.2 Decomposing the Covariance Matrix: the Freeman-Durden Approach 301
8.5.2.3 Decomposing the Coherency Matrix: the Cloude-Pottier Approach 305
8.5.2.4 Coherency Shape Parameters as Features for PolInSAR Classification 317
8.6 Interferometric Coherence as a Discriminator 319
8.7 Some Comparative Classification Results 320
8.8 Finding Pixel Vertical Detail Using Interferometric Coherence 323
CHAPTER 9 PASSIVE MICROWAVE IMAGING 326
9.1 Introduction 326
9.2 Radiometric Brightness Temperature 327
9.3 Relating Microwave Emission to Surface Characteristics 328
9.4 Emission from Rough Surfaces 331
9.5 Dependence on Surface Dielectric Constant 332
9.6 Sea Surface Emission 333
9.7 Brightness Temperature of Volume Media 335
9.8 Layered Media: Vegetation over Soil 335
9.9. Passive Microwave Remote Sensing of the Atmosphere 337
APPENDIX A COMPLEX NUMBERS 338
APPENDIX B MATRICES 343
B.1 Matrices and Vectors, Matrix Multiplication 343
B.2. Indexing and Describing the Elements of a Matrix 344
B.3 The Kronecker Product 345
B.4 The Trace of a Matrix 345
B.5 The Identity Matrix 345
B.6 The Transpose of a Matrix or a Vector 346
B.7 The Determinant 347
B.8 The Matrix Inverse 348
B.9 Special Matrices 348
B.10 The Eigenvalues and Eigenvectors of a Matrix 349
B.11 Diagonalisation of a Matrix 350
B.12 The Rank of a Matrix 351
APPENDIX C SI SYMBOLS AND METRIC PREFIXES 352
APPENDIX D IMAGE FORMATION WITH SYNTHETIC APERTURE RADAR 353
D.1 Summary of the Process 353
D.2 Range Compression 355
D.3 Compression in Azimuth 356
D.4 Look Summing for Speckle Reduction 356
D.5 Range Curvature 359
D.6 Side Lobe Suppression 361
APPENDIX E BACKSCATTER AND FORWARD SCATTER ALIGNMENT COORDINATE SYSTEMS 364
INDEX 367

Produkt-Details

• Erscheint lt. Verlag: 8.10.2009
• Reihe/Serie: Signals and Communication Technology
• Zusatzinfo: XIX, 361 p.
• Verlagsort: Berlin
• Sprache: englisch
• Themenwelt: Mathematik / Informatik ► Informatik ► Grafik / Design
• Themenwelt: Technik ► Elektrotechnik / Energietechnik
• Themenwelt: Technik ► Nachrichtentechnik
• Schlagworte: Backscattering • Cultural Structures • ecotoxicology • Interferometry • Natural Media • Polarimetry • Remote Sensing • SAR
• ISBN-10: 3-642-02020-8 / 3642020208
• ISBN-13: 978-3-642-02020-9 / 9783642020209