Remote sensing for environmental sciences ed. by Erwin Schanda. Contributors: R. T. H. Collis .

The public's serious concern about the uncertainties and dangers of the conse- quences of human activities on environmental quality demands policies to control the situation and to prevent its deterioration. But far-reaching decisions on the environmental policy are impaired or even made impossible as long as the relevant ecological relations are not sufficiently understood and large-scale quantitative information on the most important parameters is not available in sufficient quality and quantity. The techniques of remote sensing offer new ways of procuring data on natural phenomena with three main advantages - the large distance between sensor and object prevents interference with the environmental conditions to be measured, - the potentiality for large-scale and even global surveys yields a new dimension for the investigations of the environmental parameters, - the extremely wide, spectral range covered by the whole diversity of sensors discloses many properties of the environmental media not detectable within a single wave band (as e.g. the visible). These significant additions to the conventional methods of environmental studies and the particular qualification of several remote sensing methods for quantitative determination of the natural parameters makes this new investigation technique an important tool both to the scientists studying the ecological relationship and the administration in charge of the environmental planning and protection.

1. Introductory Remarks on Remote Sensing.- 1.1 Application Areas of Remote Sensing.- 1.2 Sensing Systems.- 1.3 Remote Sensing and Spectral Constraints.- 2. Aerospace Photography.- 2.1 Introduction.- 2.2 Characteristics of Photographic Process.- 2.2.1 Sensitometry — General.- 2.2.2 The Characteristic Curve.- 2.2.3 Development Control.- 2.2.4 Exposure Control.- 2.2.5 Film Speed.- 2.2.6 Reciprocity Law Anomalies.- 2.2.7 Density Measurement.- 2.2.8 Measurement of Color.- 2.2.9 Tone Reproduction Theory.- 2.2.10 Spectral Sensitivity.- 2.2.11 Resolution.- 2.2.12 Granularity.- 2.2.13 Dimensional Stability and Mechanical Properties.- 2.3 Cameras and Films.- 2.3.1 Cameras (General).- 2.3.2 Aerial Cameras — Common Features.- 2.3.3 Optical System.- 2.3.4 Calibration.- 2.3.5 Image Motion.- 2.3.6 Hand Held Cameras.- 2.3.7 Special Cameras.- 2.3.8 Film (General).- 2.3.9 Aerial Photographic Materials.- 2.3.10 Black-and-White Camera Films.- 2.3.11 Color Camera Films.- 2.4 Photographic Attributes of Earth Sciences.- 2.4.1 Agriculture.- 2.4.2 Geography and Geology.- 2.4.3 Hydrology and Oceanography.- 2.4.4 Anomalies, Atmospheric.- 2.4.5 Factors Affecting the Photo Image.- 2.4.6 Image Formation on Color Film.- 2.4.7 Processing of Color Film.- 2.4.8 Photo Systems, Choice.- 2.4.9 Image Enhancement Procedure.- 3 Infrared Sensing Methods.- 3.1 Introduction.- 3.2 The Infrared Radiation Field.- 3.3 Fundamentals of Measurement.- 3.4 Methods of Measurement.- 3.4.1 The Single Element Radiometer.- 3.4.2 Imaging Radiometers.- 3.4.3 Multi Wavelength Channel Radiometers.- 3.4.4 Spectrometers.- 3.4.5 Interferometers.- 3.5 Applications.- 3.6 Data Interpretation Error Sources.- 3.7 Expectations of the Near Future.- References.- 4 Laser Applications in Remote Sensing.- 4.1 Introduction.- 4.1.1 Scope and Definitions.- 4.1.2 Technical Approaches.- 4.2 Fundamentals of Physical Processes Involved.- 4.2.1 Specular Reflection and Elastic (Non-resonant) Scattering.- 4.2.2 Inelastic and Resonant Scattering.- 4.2.3 Resonant Absorption.- 4.2.4 Doppler Effects.- 4.2.5 Polarization.- 4.3 Instrumentation.- 4.3.1 System Concepts.- 4.3.2 System Configuration.- 4.3.3 Lasers.- 4.3.4 Photodetection.- 4.3.5 Eye Safety.- 4.3.6 Viewpoint of Remote Sensing.- 4.4 Applications.- 4.4.1 General.- 4.4.2 Backscattering Techniques — Non-resonant Elastic Scattering.- 4.4.3 Inelastic and Resonant Backscattering.- 4.4.4 Resonant Absorption.- 4.4.5 Doppler Techniques.- 4.4.6 Polarization.- References.- 5 Radar Methods.- 5.1 General Aspects.- 5.1.1 Introduction.- 5.1.2 Resolution.- 5.1.3 Image Build-up; Flight Procedure.- 5.1.4 Parallax.- 5.1.5 Image Correction.- 5.1.6 Registration of the Radar Signals.- 5.2 Backgrounds.- 5.2.1 Introduction.- 5.2.2 The Radar Equation.- 5.2.3 Ground Returns.- 5.3 Applications.- 5.3.1 Introduction.- 5.3.2 Geography.- 5.3.3 Geology.- 5.3.4 Vegetation Studies.- 5.3.5 Sea, Coastal and Oceanographic Studies.- 5.4 Conclusion.- References.- 6 Passive Microwave Sensing.- 6.1 Principles of Passive Microwave Remote Sensing.- 6.1.1 Physical Fundamentals of Microwave Radiometry.- 6.1.2 Semitransparent Media.- 6.1.3 The Effects of the Atmosphere.- 6.2 Instrumental Aspects of Microwave Radiometry.- 6.2.1 The Sensitivity of a Microwave Radiometer.- 6.2.2 Other Types of Radiometers.- 6.2.3 Angular Resolution and Range of Passive Microwave Sensing.- 6.2.4 Realisations of Microwave Radiometers.- 6.3 Emissive Properties of Materials on the Surface of the Earth.- 6.3.1 Plane Surfaces of Homogeneous Materials.- 6.3.2 Heterogeneous Media.- 6.3.3 Rough Surfaces.- 6.3.4 Various Investigations on Emissivities.- 6.4 Remote Determination of Atmospheric Constituents by Their Microwave Spectra.- 6.4.1 The Absorption Coefficients of the Line Spectra.- 6.4.2 Determinations of Height Profiles.- 6.5 Passive Microwave Remote Sensing of Water, Ice and Snow.- 6.5.1 Investigations of Water Surfaces.- 6.5.2 Investigations of Ice and Snow.- 6.6 Investigations of the Soil, Vegetation and Geological Features.- 6.7 Investigations of the Atmosphere and of Meteorological Features.- 6.7.1 Sounding of Atmospheric Constituents from Molecular Line Radiation.- 6.7.2 Observation of Meteorological Features.- References.- 7 Applications of Gamma Radiation in Remote Sensing.- 7.1 The Natural Gamma-radiation Field.- 7.2 Gamma-ray Detector Systems.- 7.3 Operational Procedures.- 7.3.1 Background Radiation.- 7.3.2 Height Correction.- 7.3.3 Calibration and Spectral Stripping.- 7.4 Applications.- 7.4.1 Mineral Exploration.- 7.4.2 Geological Mapping.- 7.4.3 Water-equivalent Snow Measurements.- 7.4.4 Soil Moisture Measurement.- 7.4.5 Monitoring Nuclear Facilities.- 7.5 Future Prospects.- References.- 8 Sonar Methods.- 8.1 Introduction.- 8.2 Propagation of Acoustic Energy.- 8.2.1 General.- 8.2.2 Absorption Losses in Water.- 8.2.3 Beam Bending in Water.- 8.2.4 Propagation in Air.- 8.3 The Sonar Equation.- 8.3.1 Transducers and Arrays.- 8.3.2 Noise and Reverberation.- 8.3.3 Signal to Noise Ratio and Signal to Reverberation Ratio.- 8.3.4 Interference Signals in Air.- 8.4 Factors Affecting Resolution in a Sonar System.- 8.4.1 General.- 8.4.2 Range Resolution.- 8.4.3 Bearing Resolution.- 8.4.4 Doppler Effect in Sonar.- 8.5 Applications.- 8.5.1 Echo Sounding.- 8.5.2 Sonars with Fixed Beams.- 8.5.3 Mechanically Rotated Sonar Array Systems.- 8.5.4 Side-scan Sonars.- 8.5.5 Sub-bottom Profiling Systems.- 8.5.6 Sonars with Sectors Scanned Electronically.- 8.5.7 Remote Sensing Application of Sonar in Air.- References.- 9. Digital Picture Processing.- 9.1 Introduction.- 9.1.1 General Remarks.- 9.1.2 Relation between Image and Real Scene.- 9.1.3 Enhancement and Filtering.- 9.2 The Elements of an Image Data Processing and Analysis System.- 9.2.1 Data Acquisition Subsystem.- 9.2.2 Data Handling Subsystem.- 9.2.3 Data Preprocessing Subsystem.- 9.2.4 Data Storage and Retrieval Subsystem.- 9.3 Geometric Corrections.- 9.3.1 Linear Transformations.- 9.3.2 Quadratic and Higher Order Transformations.- 9.3.3 Reference Marks.- 9.3.4 Image Gridding.- 9.3.5 Image Registration.- 9.3.6 Geometric Correction Concepts.- 9.4 Image Enhancement and Filtering Processes.- 9.4.1 Enhancement Processes.- 9.4.2 Image Smoothing.- 9.4.3 Image Sharpening.- 9.4.4 Matched Filters.- 9.4.5 Ratio Mapping and Generalization of Image Combination Procedures.- 9.4.6 Pseudocolor Transformation.- 9.5 Feature Extraction and Classification.- 9.5.1 Spectral Features.- 9.5.2 Spatial Features.- 9.5.3 The Decision Process.- 9.5.4 The Decision Criteria.- 9.5.5 Unsupervised Classification.- 9.5.6 Recognizing of Bridges, Rivers, Lakes, and Islands.- 9.6 Appendix 1: The Image Signal in Spatial and Frequency Domain.- 9.6.1 Signals in the Spatial Domain.- 9.6.2 Signals in the Frequency Domain.- 9.7 Appendix 2: Numerical Example for Texture-context Features.- References.- Color Plates.