Synthetic Aperture Radar Polarimetry E-Book

Jakob J. van Zyl

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Serie: JPL Space Science and Technology Series
• Sprache: Englisch

Seitenzahl: 402

Veröffentlichungsjahr: 2011

Beschreibung

This book describes the application of polarimetric synthetic aperture radar to earth remote sensing based on research at the NASA Jet Propulsion Laboratory (JPL). This book synthesizes all current research to provide practical information for both the newcomer and the expert in radar polarimetry. The text offers a concise description of the mathematical fundamentals illustrated with many examples using SAR data, with a main focus on remote sensing of the earth.

The book begins with basics of synthetic aperture radar to provide the basis for understanding how polarimetric SAR images are formed and gives an introduction to the fundamentals of radar polarimetry. It goes on to discuss more advanced polarimetric concepts that allow one to infer more information about the terrain being imaged. In order to analyze data quantitatively, the signals must be calibrated carefully, which the book addresses in a chapter summarizing the basic calibration algorithms. The book concludes with examples of applying polarimetric analysis to scattering from rough surfaces, to infer soil moisture from radar signals.

Leseprobe

Contents

Cover

Series

Title Page

Copyright

Dedication

NOTE FROM THE SERIES EDITOR

FOREWORD

PREFACE

ACKNOWLEDGMENTS

AUTHORS

CHAPTER 1: SYNTHETIC APERTURE RADAR (SAR) IMAGING BASICS

1.1 BASIC PRINCIPLES OF RADAR IMAGING

1.2 RADAR RESOLUTION

1.3 RADAR EQUATION

1.4 REAL APERTURE RADAR

1.5 SYNTHETIC APERTURE RADAR

1.6 RADAR IMAGE ARTIFACTS AND NOISE

1.7 SUMMARY

CHAPTER 2: BASIC PRINCIPLES OF SAR POLARIMETRY

2.1 POLARIZATION OF ELECTROMAGNETIC WAVES

2.2 MATHEMATICAL REPRESENTATIONS OF SCATTERERS

2.3 IMPLEMENTATION OF A RADAR POLARIMETER

2.4 POLARIZATION RESPONSE

2.5 OPTIMUM POLARIZATIONS

2.6 CONTRAST ENHANCEMENT

2.7 SUMMARY

CHAPTER 3: ADVANCED POLARIMETRIC CONCEPTS

3.1 VECTOR-MATRIX DUALITY OF SCATTERER REPRESENTATION

3.2 EIGENVALUE- AND EIGENVECTOR-BASED POLARIMETRIC PARAMETERS

3.3 DECOMPOSITION OF POLARIMETRIC SCATTERING

3.4 IMAGE CLASSIFICATION

3.5 POLARIMETRIC SAR INTERFEROMETRY

3.6 SUMMARY

CHAPTER 4: POLARIMETRIC SAR CALIBRATION

4.1 POLARIMETRIC RADAR SYSTEM MODEL

4.2 CROSS TALK ESTIMATION AND REMOVAL

4.3 COPOLARIZED CHANNEL IMBALANCE CALIBRATION

4.4 ABSOLUTE RADIOMETRIC CALIBRATION

4.5 FARADAY ROTATION

4.6 SUMMARY

CHAPTER 5: APPLICATIONS: MEASUREMENT OF SURFACE SOIL MOISTURE

5.1 SURFACE ELECTRICAL AND GEOMETRICAL PROPERTIES

5.2 SCATTERING FROM BARE ROUGH SURFACES

5.3 EXAMPLE BARE SURFACE SOIL MOISTURE INVERSION MODELS

5.4 COMPARISON OF THE PERFORMANCE OF BARE SURFACE INVERSION MODELS

5.5 PARAMETERIZING SCATTERING MODELS

5.6 INVERTING THE IEM MODEL

5.7 SCATTERING FROM VEGETATED TERRAIN

5.8 SIMULATION RESULTS

5.9 TIME SERIES ESTIMATION OF SOIL MOISTURE

5.10 SUMMARY

APPENDIX A: TILTED SMALL-PERTURBATION MODEL DETAILS

APPENDIX B: BISTATIC SCATTERING MATRIX OF A CYLINDER WITH ARBITRARY ORIENTATION

APPENDIX C: NOMENCLATURE

C.1 ACRONYMS AND ABBREVIATIONS

C.2 COMMONLY USED SYMBOLS

Plates

Index

JPL SPACE SCIENCE AND TECHNOLOGY SERIESJoseph H. Yuen, Editor-in-ChiefPublished Titles in this Series

Fundamentals of Electric Propulsion: Ion and Hall Thrusters Dan M. Goebel and Ira Katz

Synthetic Aperture Radar Polarimetry Jakob Van Zyl and Yunjin Kim

Copyright © 2011 by John Wiley & Sons, Inc. All rights reserved.

Published by John Wiley & Sons, Inc., Hoboken, New Jersey. Published simultaneously in Canada.

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Library of Congress Cataloging-in-Publication Data is available

ISBN: 978-1-118-11511-4

oBook ISBN: 978-1-118-11610-4

ePDF ISBN: 978-1-118-11607-4

ePub ISBN: 978-1-118-11609-8

eMobi ISBN: 978-1-118-11608-1

Synthetic Aperture Radar Polarimetry

December 2010

The research described in this publication was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not constitute or imply its endorsement by the United States Government or the Jet Propulsion Laboratory, California Institute of Technology.

NOTE FROM THE SERIES EDITOR

The Jet Propulsion Laboratory (JPL) Space Science and Technology Series broadens the range of the ongoing JPL Deep Space Communications and Navigation Series to include disciplines other than communications and navigation in which JPL has made important contributions. The books are authored by scientists and engineers with many years of experience in their respective fields, and lay a foundation for innovation by communicating state-of-the-art knowledge in key technologies. The series also captures fundamental principles and practices developed during decades of space exploration at JPL, and celebrates the successes achieved. These books will serve to guide a new generation of scientists and engineers.

We would like to thank the Office of the Chief Scientist and Chief Technologist for their encouragement and support. In particular, we would like to acknowledge the support of Thomas A. Prince, former JPL Chief Scientist; Erik K. Antonsson, former JPL Chief Technologist; Daniel J. McCleese, JPL Chief Scientist; and Paul E. Dimotakis, JPL Chief Technologist.

JOSEPH H. YUEN, Editor-in-Chief

JPL Space Science and Technology Series Jet Propulsion Laboratory California Institute of Technology

FOREWORD

I am very pleased to commend the Jet Propulsion Laboratory (JPL) Space Science and Technology Series, and to congratulate and thank the authors for contributing their time to these publications. It is always difficult for busy scientists and engineers, who face the constant pressures of launch dates and deadlines, to find the time to tell others clearly and in detail how they solved important and difficult problems, so I applaud the authors of this series for the time and care they devoted to documenting their contributions to the adventure of space exploration.

JPL has been NASA's primary center for robotic planetary and deep-space exploration since the Laboratory launched the nation's first satellite, Explorer 1, in 1958. In the 50 years since this first success, JPL has sent spacecraft to all the planets except Pluto, studied our own planet in wavelengths from radar to visible, and observed the universe from radio to cosmic ray frequencies. Current plans call for even more exciting missions over the next decades in all these planetary and astronomical studies, and these future missions must be enabled by advanced technology that will be reported in this series. The JPL Deep Space Communications and Navigation book series captured the fundamentals and accomplishments of these two related disciplines, and we hope that this new series will expand the scope of those earlier publications to include other space science, engineering, and technology fields in which JPL has made important contributions.

I look forward to seeing many important achievements captured in these books.

CHARLES ELACHI, Director

Jet Propulsion Laboratory California Institute of Technology

PREFACE

The fundamentals of radar polarimetry were built on a long history of research in optics. However, the fact that the radar is an active instrument, allowing one the extra flexibility to change the polarization of the transmitted wave in addition to optimizing the receiving antenna polarization, opened new doors to more powerful analysis of scattering from different types of terrain.

This book describes the application of polarimetric synthetic aperture radar to Earth remote sensing based on our research at the Jet Propulsion Laboratory (JPL). Many important contributions to the field of radar polarimetry were made long before we joined the field. Giants in the field include Kennaugh, Sinclair, Huynen, Boerner, and many others. Our contribution is to put their work to practice in the field of synthetic aperture radar (SAR), but we owe thanks to these pioneers for pointing the way.

There is a vast amount of literature available on radar polarimetry. Here we did not try to reproduce or summarize all of these publications. Instead, we concentrated our effort on compiling a subset of the knowledge into a reference that we hoped would prove useful to both the newcomer and the expert in radar polarimetry. We provide a concise description of the mathematical fundamentals illustrated with many examples using SAR data. Our treatment of the subject is focused on remote sensing of the Earth, and the examples are chosen to illustrate this application.

We start with the basics of synthetic aperture radar to provide the basis for understanding how polarimetric SAR images are formed. We follow this introduction with the fundamentals of radar polarimetry. We next discuss some of the more advanced polarimetric concepts that allow one to infer more information about the terrain being imaged. In order to analyze data quantitatively, however, the signals must be calibrated carefully. We included a chapter summarizing the basic calibration algorithms. We conclude our discussion with an example of the application of polarimetric analysis to scattering from rough surfaces with the aim to infer soil moisture from the radar signals.

Much still remains to be discovered about the best ways to extract all the information out of polarimetric SAR data. We hope that by preparing this work we have helped to accelerate this process by providing the next generation of researchers with some of the tools to make those discoveries.

JAKOB VAN ZYL AND YUNJIN KIM

Pasadena, California December 2010

ACKNOWLEDGMENTS

We would like to express our appreciation to Joseph H. Yuen for his encouragement of us in generating this book and to Roger Carlson, Judi Dedmon, and John Kovacic for their editing and layout. We also thank all of our colleagues who contributed by providing us with the excellent synthetic aperture radar data. We have been privileged to work with them over the years. Likewise, through the years, we have collaborated with many researchers all over the globe. We thank them for their help in shaping our insight into the analysis of polarimetric SAR data.

December 2010

AUTHORS

Jakob van Zyl received his Hons. B. Engineering (Cum Laude) in electronics engineering from the University of Stellenbosch, South Africa in 1979. Dr. van Zyl received his M.S. and Ph.D. in electrical engineering from the California Institute of Technology (Pasadena, California) in 1983 and 1986, respectively. He has been with the Jet Propulsion Laboratory in Pasadena, California since 1986. At JPL he contributed to the design and development of many synthetic aperture radar (SAR) systems, including SIR-C, SRTM, AIRSAR, TOPSAR, and GeoSAR. In 1997 he received the Fred Nathanson Memorial Radar Award for advancement of radar polarimetry, radar interferometry, and synthetic aperture radar from the Aerospace and Electronics Society of the IEEE. In 2010 he received the Distinguished Achievement Award from the Geoscience and Remote Sensing Society of the IEEE for his contributions to polarimatric SAR remote sensing. He is currently the Associate Director for Project Formulation and Strategy at the Jet Propulsion Laboratory.

Yunjin Kim received his B.S. in electrical engineering from the California State University, Sacramento, in 1983. Dr. Kim received his M.S. and Ph.D. in electrical engineering from the University of Pennsylvania (Philadelphia, Pennsylvania) in 1985 and 1987, respectively. From 1987 to 1989, he was with the Department of Electrical Engineering, New Jersey Institute of Technology (Newark), as an assistant professor. Since 1989, Dr. Kim has been with the Jet Propulsion Laboratory (JPL), California Institute of Technology. At JPL, Dr. Kim has contributed to the development of several radar systems such as SIR-C, AIRSAR, GeoSAR, and SRTM. Currently, he is the Nuclear Spectroscopic Telescope Array (NuSTAR) project manager.

CHAPTER 1

SYNTHETIC APERTURE RADAR (SAR) IMAGING BASICS

The word “radar” is an acronym for “radio detection and ranging.” A radar measures the distance, or range, to an object by transmitting an electromagnetic signal to and receiving an echo reflected from the object. Since electromagnetic waves propagate at the speed of light, one only has to measure the time it takes the radar signal to propagate to the object and back to calculate the range to the object. The total distance traveled by the signal is twice the distance between the radar and the object, since the signal travels from the radar to the object and then back from the object to the radar after reflection. Therefore, once we measured the propagation time (t), we can easily calculate the range (R) as

(1-1)

where c is the speed of light in a vacuum. The factor ½ accounts for the fact that the radar signal actually traveled twice the distance measured: first from the radar to the object and then from the object to the radar. If the electric property of the propagation medium is different from that of the vacuum, the actual propagation velocity has to be estimated for advanced radar techniques, such as synthetic aperture radar (SAR) interferometry.

Radars provide their own signals to detect the presence of objects. Therefore, radars are known as active, remote-sensing instruments. Because radars provide their own signal, they can operate during day or night. In addition, radar signals typically penetrate clouds and rain, which means that radar images can be acquired not only during day or night but also under (almost) all weather conditions. For these reasons, radars are often referred to as all-weather instruments. Imaging, remote-sensing radars, such as SAR, produce high-resolution (from submeter to a few tens of meters) images of surfaces. The geophysical information can be derived from these high-resolution images by using proper postprocessing techniques.

This book focuses on a specific class of implementation of synthetic aperture radar with particular emphasis on the use of polarization to infer the geophysical properties of the scene. As mentioned above, SAR is a way to achieve high-resolution images using radio waves. We shall first describe the basics of radar imaging. This shall be followed by a description of the synthetic aperture principle. Finally, we shall discuss some advanced SAR implementations, such as SAR polarimetry and polarimetric SAR interferometry.

1.1 BASIC PRINCIPLES OF RADAR IMAGING

Imaging radars generate surface images that are at first glance very similar to the more familiar images produced by instruments that operate in the visible or infrared parts of the electromagnetic spectrum. However, the principle behind the image generation is fundamentally different in the two cases. Visible and infrared sensors use a lens or mirror system to project the radiation from the scene on a “two-dimensional array of detectors,” which could be an electronic array or, in earlier remote-sensing instruments, a film using chemical processes. The two-dimensionality can also be achieved by using scanning systems or by moving a single line array of detectors. This imaging approach—an approach with which we are all familiar from taking photographs with a camera—conserves the relative angular relationships between objects in the scene and their images in the focal plane, as shown in . Because of this conservation of angular relationships, the resolution of the images depends on how far away the camera is from the scene it is imaging. The closer the camera, the higher the resolution and the smaller the details that can be recognized in the images. As the camera moves further away from the scene, the resolution degrades and only larger objects can be discerned in the image.