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Review Essays of Academic, Professional & Technical Books in the Humanities & Sciences


Introduction to Microwave Remote Sensing by Iain H. Woodhouse (CRC Press) Introduction to Microwave Remote Sensing offers an extensive overview of this versatile and extremely precise technology for technically oriented undergraduates and graduate students.

This textbook emphasizes an important shift in conceptualization and directs it toward students with prior knowledge of optical remote sensing: the author dispels any linkage between microwave and optical remote sensing. Instead, he constructs the concept of microwave remote sensing by comparing it to the process of audio perception, explaining the workings of the ear as a metaphor for microwave instrumentation.

This volume takes an "application-driven" approach. Instead of describing the technology and then its uses, this textbook justifies the need for measurement then explains how microwave technology addresses this need.

Following a brief summary of the field and a history of the use of microwaves, the book explores the physical properties of microwaves and the polarimetric properties of electromagnetic waves. It examines the interaction of microwaves with matter, analyzes passive atmospheric and passive surface measurements, and describes the operation of altimeters and scatterometers. The textbook concludes by explaining how high resolution images are created using radars, and how techniques of interferometry can be applied to both passive and active sensors.


  • Provides an extensive introduction to the fundamentals of both active and passive microwave remote sensing

  • Discusses the fundamentals of interference and coherence

  • Summarizes key bio- and geo-physical variables that influence the emission and scattering of microwaves

  • Margin notes provide easy reference while maintaining the flow of the text The Appendix summarizes useful mathematics, including logarithms, trigonometry, matrices, and complex numbers

There's good news and there's bad news.

The had news is that microwave remote sensing is a difficult subject. It requires a fair hit of mathematics and physics to be able to understand many of the topics and there are many novel concepts that will seem rather difficult to grasp first time around. Coherence. Polarimetry. Interference. If these are new to you, then don't panic. They are difficult concepts and will take a while to get used to. But remember: "perseverance furthers".

As my contribution, I've tried to make sure that the more challenging material can be skimmed over without loss of consistency in the rest of the text. There are more words than equations in this text. I've done that to put the emphasis on ideas and concepts, rather than the detailed physics behind them. But sooner or later, if you want to truly get to grips with microwave remote sensing, you will have to tackle some mathematics and basic physics.

But there's good news...

The good news is that microwave remote sensing is fascinating. It's only really now, as we enter the 21st century, that microwave techniques in Earth observation have matured out of infancy and are starting to make a real impact on the our understanding and management of planet Earth. Perhaps more than any other remote sensing technique (and I write with a clear bias) microwaves are unique in their scope, their range of applications, their versatility and their quite staggering ability to make quantitative measurements. From a distance of 800km, microwave instruments can make centimetre-scale measurements of the ground surface, or determine atmospheric concentrations to within parts per billion.

It is no longer the case that remote sensing professionals can live with-out understanding the basics of microwave techniques. But because of its complexity of ideas and the intensity of some of the mathematics and physics behind it, microwave remote sensing risks always remaining elitist and apparently inaccessible. My intentions for this text were, if nothing else, to offer some kind of peek over the fence into the realms of microwave remote sensing, and at least gain enough knowledge to adopt respect and wonder.

To this end, I've included a few things to help make the book easier to use. The margin notes allow easy reference without disturbing the flow of the text. I have tried to explain the steps in mathematical derivations, and there is an appendix summarising some useful mathematics, including logarithms, trigonometry, matrices and complex numbers. Equations are usually accompanied by the relevant units in square brackets. And I have also tried to emphasise the shift in conceptualisation that is required for those readers with some prior knowledge of optical remote sensing. In particular, following the brief summary of microwave remote sensing in Chapter I , Chapter 2 begins the book proper with a summary of the history of the subject. This is included not simply for background, but to dispel any thoughts you might have of linking the history of microwave remote sensing to that of optical remote sensing. The two are barely even distant cousins when it conies to their heritage, and giving this historical context is an important first step in establishing the special nature of microwaves and how they are exploited.

This is followed by the basic physics of the subject in Chapters 3 (the physical properties of microwaves themselves) and 4 (the polarimetric properties of electromagnetic waves). The first of these chapters includes some extremely important material on the fundamental principles of interference and coherence.

Chapter 5 then explores the physics of how microwaves interact with matter. The underlying rationale for any remote sensing technique is that you can measure some useful physical property of the Earth's surface or atmosphere. This chapter summarises the key bio- and geo-physical variables that influence the emission and scattering of microwaves.

My other approach to help readers conceptualise this subject differently, is to make comparisons between microwave systems and audio perception. This is most apparent in Chapter 6 where the workings of the ear, rather than the eye, are explained as a metaphor for microwave instrumentation.

Two chapters then deal with passive atmospheric measurements and passive surface measurements. The rest of the chapters relate to specific techniques or methods of microwave radar. And 1 apologise in advance for having a clear bias to these techniques — this is my research area, and so it is always easy to find more to say about these topics. Chapter 9 deals with general radar principles and describes the operation of altimeters and scatterometers. Chapter 10 then expands on these ideas to describe how high resolution images can be created using radars and finally, Chapter 11 describes the techniques of interferornetry for both passive and active sensors.

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