Erwin Schanda Physical Fundamentals of Remote Sensing With 102 Figures and 14 Tables Springer -Verlag Berlin Heidelberg New York Tokyo
Professor Dr. ERWIN SCHANDA University of Bern Institute of Applied Physics SidlerstraBe 5 3012 Bern, Switzerland ISBN-13: 978-3-540-16236-0 e~isbn-13: 978-3-642-48733-0 DOl: 10.1007/978-3-642-48733-0 Libray of Congress Cataloging-in-Publication Data. Schanda, Erwin. Physical fundamentals of remote sensing. Includes index. 1. Remote sensing I. Title. G70.4.S34 1986 621.36'78 85-31735 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically those of translation, reprinting, re-use of illustrations, broadcasting, reproduction by photocopying machine or similar means, and storage in data banks. Under 54 of the German Copyright Law where copies are made for other than private use a fee is payable to 'Verwertungsgesellschaft Wort', Munich. by Springer-Verlag Berlin Heidelberg 1986 The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Typesetting: K + V Fotosatz GmbH, Beerfelden 2132/3130-543210
Preface Ten years ago the author, together with eight co-authors, edited a textbook Remote Sensing for Environmental Sciences within the series on Ecological Studies of Springer-Verlag. At that time there were not yet many books available on remote sensing. The decade that has elapsed was marked by a spectacular development in this field. This development took place in many directions: by widening the areas of application, by improvements of the methods and the sensors, by the introduction of new versatile platforms, but also by deepening the knowledge of the theoretical foundations. This evolution improved the ability to explain the interaction between electromagnetic radiation and natural objects, which, in its turn, allowed for better modelization and for the creation of refined mathematical tools in the processing of remotely sensed data and in the determination of the physical status of remote objects. The community of research workers engaged in development and use of remote sensing methods changed accordingly from a modest group of scientists in the early 1970's to a considerable branch of specialized and interdisciplinary activity. The training of students had to be adapted to cope with the increasing number of people entering this new field and with the increasing quality of the material to be presented. At present scientists exchange their results at many international conferences each year, and the annual production of publications in various related scientific journals amounts to several thousands of pages in addition to the growing number of monographs and manuals. One could ask for what purpose should one publish another book? According to the author's experience, however, there is a serious neglect of systematic study and education about important physical fundamentals. The present text is the result of the author's graduate course as it evolved during the last 6 years. This subject, under the title Physikalische Grundlagen der Fernerkundung fur Naturwissenschaftler was presented as a course for the first time during the summer term of 1979 at the University of Bern, Switzerland. The material was considerably supplemented and arranged in a shape very much like the present text when the lectures were presented at the Universite Paul Sabatier, Toulouse, France, during the academic years 1982/83
VI Preface and 1983/84 under the title Interaction du rayonnement electromagnetique et des milieux naturels. Within the limits ofthe present volume, no complete treatment of all significant physical fundamentals of remote sensing is possible. Therefore, topics were selected which are, according to the personal judgement and taste of the author, most important for the comprehension of physical relationships relevant in the methods of remote sensing and their applications to the environment. However, neither mathematical methods, such as, for example for data and image processing, nor the environmental phenomena and processes were intended to be treated within this text. The material is arranged in 15 sections (5 chapters containing 3 sections each), approximately corresponding to a course of 15 lectures. A didactic development from very basic relations at the beginning to a rather demanding level in the last sections has been striven for. This text, as well as the lectures from which it was derived, is intended primarily for graduate students of natural sciences, for research workers in environmental sciences, and for remote sensing practitioners. The increasing degree of difficulty in the physical concepts, as well as in the mathematical methods, may cause readers of differing background knowledge to skip the one or the other section which is of less significance to their specific interest. In most cases it will be possible to continue at a subsequent chapter because in the more advanced chapters reference is only made to those of the previous sections which are related to and needed for the topic under discussion. Students of physics are expected to know most of the essentials of this text; however, it can serve to become aware which areas of physics may be relevant for use in remote sensing. It was not the author's intention to present the newest methods of remote sensing, either to discuss the most recent details of technical developments of sensor systems and space platforms, or to describe many observational results in a phenomenological way as it is done in many texts on remote sensing. However, it is his hope to rouse the appreciation and understanding of the physical background and to create a consciousness of the importance of the interaction of electromagnetic radiation with matter for optimum use of remote sensing. Finally, it is with great pleasure and gratitude that the author wishes to acknowledge the considerable share of a number of persons in the realization of this textbook. In the first place, I should like to thank Francis Cambou and Thuy Le Toan for the opportunity of a 6- month stay at the Centre d'etude Spatiale des Rayonnements, Universite Paul Sabatier, Toulouse, during a sabbatical semester 1982. There, for the first time, I had the opportunity to arrange and
Preface VII present these lectures in essentially their present form. The following colleagues at various institutions abroad helped considerably to improve the presentation and, in particular, to correct the language of different parts in this text (in alphabetical order): J. A. Kong, Massachusetts Institute of Technology R. W. Larson, Environmental Research Institute of Michigan R. K. Moore, University of Kansas P. W. Rosenkranz, Massachusetts Institute of Technology F. T. Ulaby, University of Michigan D. Walshaw, University of Oxford E. R. Westwater, U.S. National Oceanic and Atmospheric Administration Several of my colleagues at the University of Bern provided me with very valuable comments and suggestions, which helped to improve many formulations: Th. Binkert, D.A. Deranleau, R. Keese, K. Kiinzi, C. Matzler. A large portion of the figures were drawn with great care, and many others were adapted for printing, by Mr. J. Bronnimann. By far the heaviest workload, however, has been carried by the secretaries of the Institute of Applied Physics, Bern, Mrs. M. Swain, Mrs. K. Gutknecht, and Mrs. B. Schweingruber, in typing, correcting and retyping the manuscript. I also wish to thank the publishing company, Springer-Verlag, for valuable advice and efficient co-operation. Last, but not least, my warmest thanks are due to my family for the patience during the time with the burden of additional work. ERWIN SCHANDA
Contents 1 Some Basic Relations 1 1.1 Natural Parameters and Observables. 1 1.2 Propagation of Electromagnetic Waves 9 1.3 Waves at Boundaries Between Different Media 22 2 Spectral Lines of Atmospheric Gases. 33 2.1 Resonant Frequencies of Molecules 33 2.2 Widths of Spectral Lines...... 47 2.3 Applications to the Earth's Atmosphere. 52 3 Spectral Properties of Condensed Matter.. 64 3.1 Elementary Theory of Organic Dyes 64 3.2 Chlorophyll and Spectral Properties of Plants 78 3.3 Polarization of the Media and Dispersion of Radiation 83 4 Scattering of Radiation................ 98 4.1 Light Scattering by Molecules.......... 98 4.2 Scattering of Radiation by Macroscopic Particles 106 4.3 Backscattering from Rough Surfaces 120 5 Transport of Radiation......... 136 5.1 The Equation of Radiative Transfer 136 5.2 Kirchhoff's Law and Radiometry. 143 5.3 Radiometric Observation of Atmospheric Parameters and the Inversion of Remotely Sensed Data 157 References. 176 Subject Index 181