1st Edition

Introduction to Microwave Remote Sensing

By Iain H. Woodhouse Copyright 2006
    400 Pages 87 B/W Illustrations
    by 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.

    WHY MICROWAVES?

    Overview of Microwave Systems


    Information from Passive Microwave Imagers
    Information from Passive Microwave Sounders
    Information from Active Microwave Instruments
    How Can This Information be Used?

    A BRIEF HISTORY OF MICROWAVES

    In the Beginning

    Out of the Darkness: Maxwell and Hertz

    Radios, Death Rays and Radar

    The Venus Ruler and Little Green Men

    Imaging Radar

    Microwave Remote Sensing from Space

    Further Reading

    PHYSICAL FUNDAMENTALS

    Physical Properties of EM Waves


    Electromagnetic Radiation as Waves
    Complex Wave Description

    Energy and Power of Waves


    Polarisation

    Combination of Waves


    Coherence

    The Most Important Section in This Book


    Phase as a (Relative) Distance Measure
    Combining Two Waves in 2-D
    Quantifying the Interference Pattern
    Passive Case
    Multiple Source Interference Pattern
    Beamwidth and Angular Resolution
    Huygens’ Wavelets
    More on Coherence

    Propagation of Microwaves


    Through Lossy Media
    Moving Sources

    Where Do Microwaves Come From?


    How Are They Produced in Nature?
    Radiation Laws
    How Are Microwaves Produced Artificially?

    Further Reading

    POLARIMETRY

    Describing Polarised Waves


    Summary of Linear Basis

    Superposition of Polarised Waves

    Representing Polarisation


    Poincaré sphere
    Mathematical Description
    Stokes Vector
    Brightness Stokes Vector
    Partially Polarised Waves
    The Stokes Scattering Matrix
    The Scattering Matrix
    Target Vector
    Covariance Matrix

    Passive Polarimetry

    Polarimetry in Radar


    Radar Polarimeters
    Polarimetric Synthesis and Response Curves

    Important Polarimetric Properties


    Unpolarised Power
    Degree of Polarisation and Coefficient of Variation
    Polarimetric Ratios
    Coherent Parameters
    Polarimetric Decomposition

    Further Reading

    MICROWAVES IN THE REAL WORLD

    Continuous Media and the Atmosphere


    Radiative Transfer Theory
    Microwave Brightness Temperature
    Spectral Lines
    Line Broadening
    Faraday Rotation

    Interaction With Discrete Objects


    Diffraction
    Importance of Diffraction
    Scattering
    Radar Cross-section
    Importance of Scattering Theory

    Scattering and Emission from Volumes


    Transmission Through Volumes
    Emission
    Scattering

    Reflection and Emission from Smooth Surfaces


    Scattering from Smooth Boundaries
    Emission from Smooth Boundaries
    Summary

    Scattering and Emission from Rough Surfaces


    Definition of “Rough”
    Effects of Roughness
    Summary

    Non-Random (Periodic) Surfaces

    Scattering and Emission from Natural Surfaces


    Oceans and Lakes
    Hydrometeors
    Ice and Snow
    Freshwater Ice
    Glacial Ice
    Sea Ice
    Bare Rock and Deserts
    Soils
    Vegetation

    Special Scatterers


    Corner Reflectors
    Moving Targets
    Mixed Targets

    Further Reading

    DETECTING MICROWAVES

    General Approach

    Conceptual Approach to Microwave Systems


    A Word of Warning

    Basic Microwave Radiometer

    The Antenna


    Parabolic Antennas
    The Dipole Antenna
    Array Antennas
    Antenna Properties

    The Receiver


    Detector

    Coherent Systems

    Active Systems

    System Performance


    Noise and Sensitivity
    Sensitivity Considerations for Receivers
    Other Sources of Uncertainty

    Calibration


    Antenna Calibration
    Verification and Validation
    Types of Calibration
    Strategies for Calibrating Receivers

    Final Remarks on Calibration

    Further Reading

    ATMOSPHERIC SOUNDING

    Atmospheric Sounding


    The Need for Measurements
    The Earth’s Atmosphere
    Water Vapour and Oxygen
    Clouds and Precipitation
    Ozone
    Chlorine Monoxide
    Other Relevant Measurements

    Principles of Measurement

    Theoretical Basis of Sounding


    The Forward Model
    Simple Formulation of the Forward Model
    The Inverse Model
    Solving the Inverse Problem
    The Influence Functions

    Viewing Geometries


    Nadir Sounding
    Limb Sounding

    Passive Rainfall Mapping


    The Need for Measurements
    Principles of Measurement
    Emission Method
    Scattering Method

    Further Reading

    PASSIVE IMAGING

    Principles of Measurement


    Background
    Practical Radiometers
    Viewing Geometries
    The Generic Forward Model

    Oceans


    The Need for Measurements
    Principles of Measurement: SST
    Principles of Measurement: Ocean Salinity
    Principles of Measurement: Ocean Winds

    Sea Ice


    The Need for Measurements
    Sea Ice Concentration

    Land


    The Need for Measurements
    The Forward Problem Over Land
    Empirical Approaches to Snow Depth
    A Final Comment on Passive Polarimetry

    Further Reading

    ACTIVE MICROWAVES

    Principles of Measurement


    What is RADAR?
    Basic Radar Operation

    The Generic Equations of Radar Performance


    The Radar Equation
    Range resolution

    Radar Altimeters


    The Need for Altimeter Measurements
    Altimeter Geometry
    Instrumentation
    Echo Shape Analysis
    Range Ambiguity
    Accuracy of Height Retrievals
    Scanning Altimeters
    Calibration and Validation

    Improving Directionality


    Sub-Beamwidth Resolution
    Synthetic Aperture Altimeters

    Scatterometers


    The Need for Scatterometer Measurements
    General Operation
    Rain Radar
    Windscatterometers
    Polarimetric Scatterometers

    Further Reading

    IMAGING RADAR

    The Need for Imaging Radar


    Oceans
    Sea Ice
    Terrestrial Surfaces
    The Water Cloud Model for Vegetation
    Other Uses of Radar Imagery

    What is an Image?

    Radar Image Construction

    Side-Looking Airborne Radar


    Ground Range resolution
    Azimuth Resolution
    Synthetic Aperture Radar (SAR)
    Aperture Synthesis: A Doppler Interpretation
    Aperture Synthesis: A Geometric Explanation
    Geometry vs. Doppler
    SAR Focussing

    Radar Equation for SAR

    Geometric Distortions in Radar Images


    Lay-over and Foreshortening
    Radar Shadow
    Motion Errors
    Moving Targets

    Operational Limits


    Ambiguities
    Coverage vs PRF

    Other SAR Modes


    ScanSAR Operation
    Spotlight Mode

    Working With SAR Images


    Speckle
    Speckle Statistics
    Speckle Filtering
    Geometric Correction
    Limitations of Geometric Correction

    SAR Data Formats

    Extracting Topography from SAR Images


    Stereo SAR Radargrammetry
    SAR Clinometry

    Further Reading

    INTERFEROMETRY

    The Need for Interferometric Measurements

    Principles of Interferometry


    Phase Measurements
    Application of Dual Systems
    Interferometry for Resolving Direction

    Passive Imaging Interferometry

    Radar Interferometry


    Interferometric Altimetry
    Interferometric SAR
    InSAR Viewing Geometries
    Interferometric Coherence Magnitude
    Decorrelation
    Summary of Decorrelation

    Practical DEM Generation


    InSAR Processing Chain

    Vegetation Height Estimation


    Single Frequency
    Dual-Frequency
    Polarimetric Interferometry and Multibaseline
                Interferometry
    SAR Tomography

    Differential SAR Interferometry


    Considerations and Limitations
    Atmospheric Water Vapour

    Permanent Scatterer Interferometry

    Along-Track Interferometry

    Further Reading

    APPENDIX: Summary of Useful


                Mathematics

    Angles


    Degrees
    Radians
    Steradian (solid angle)

    Some Useful Trigonometric Relations

    Logs and Exponentials


    Some Fundamental Properties
    Special values
    Series Expansions

    Complex Numbers

    Vectors


    Law of Vector Algebra
    Cross or Vector Product

    Matrices


    Matrix Algebra

    Biography

    Woodhouse, Iain H.

    “This book can serve as a textbook for graduate students on the properties of microwaves and how they can be used to study the Earth, and also as a good reference for remote sensing scientists and engineers who would like a convenient summary of relevant electromagnetic gathered in a single volume. … This book fills an important niche between classical electromagnetic textbooks and detailed application manuals, giving an appreciation of how microwave remote sensing relates discipline science to the fundamentals of radio wave propagation. … The book stands out as a worthy general text that is ideally suited for introductory coursework o tot serve as an advanced reference. This book should find its way onto many desks and bookshelves belonging to remote sensing professionals and future remote sensing professionals.”
    —In PE&RS, Vol. 73, No. 7, July 2007