Table of Contents |
1. | Introduction | 1 |
1.1. | Motivation | 1 |
1.2. | Definitions and acronyms | 2 |
1.3. | Scope of book | 3 |
2. | Automatic target recognition of ground targets | 5 |
2.1. | Introduction | 5 |
2.2. | SAR phenomenology | 7 |
2.3. | The ATR processing chain | 11 |
2.3.1. | Pre-screening | 11 |
2.3.2. | Template-matching | 14 |
2.3.3. | Feature-based classification | 15 |
2.4. | Use of contextual information in target detection | 19 |
2.4.1. | Motivation | 19 |
2.4.2. | Statistical formulation | 19 |
2.4.3. | Simulated results | 21 |
2.5. | Databases and modelling | 22 |
2.5.1. | Database construction | 22 |
2.5.2. | Case study: model-based ATR using MOCEM | 24 |
2.6. | Performance assessment | 26 |
2.6.1. | Receiver operating characteristic (ROC) curves | 26 |
2.6.2. | Confusion matrices | 29 |
2.6.3. | Operational assessment | 32 |
2.7. | Conclusions | 34 |
| Acknowledgements | 34 |
| References | 35 |
3. | Automatic recognition of air targets | 37 |
3.1. | Introduction | 37 |
3.2. | Fundamentals of the target recognition process | 38 |
3.2.1. | Introduction | 38 |
3.2.2. | Target features | 38 |
3.2.3. | Aircraft recognition techniques and waveform design | 39 |
3.2.4. | Target signature measurement | 41 |
3.2.5. | Radar range equation for radar target recognition | 42 |
3.2.6. | Main classification functions | 43 |
3.2.7. | Database | 44 |
3.2.8. | Classifier | 44 |
3.2.9. | Assembly of database | 46 |
3.2.10. | Classifier performance | 47 |
3.2.11. | Conclusions | 48 |
3.3. | Jet engine recognition | 48 |
3.3.1. | Introduction | 48 |
3.3.2. | Jet engine mechanics | 49 |
3.3.3. | Interaction of radar signal with engine blades | 49 |
3.3.4. | Jet engine modulation spectrum: engine rotational rate | 50 |
3.3.5. | Jet engine modulation spectrum: rotor stage spectrum | 52 |
3.3.6. | Jet engine modulation spectrum: mixing products from rotor stages | 54 |
3.3.7. | Determination of blade count | 55 |
3.3.8. | JEM waveform | 55 |
3.3.9. | System requirements | 56 |
3.3.10. | Conclusions | 56 |
3.4. | Helicopter recognition | 57 |
3.4.1. | Introduction | 57 |
3.4.2. | Main rotor blade flash | 57 |
3.4.3. | Detection of blade flash | 60 |
3.4.4. | Waveform and system requirements for blade flash detection | 62 |
3.4.5. | Blade flash detection | 62 |
3.4.6. | Helicopter classification using blade flash | 63 |
3.4.7. | Main rotor hub spectrum | 63 |
3.4.8. | Rear rotor blades | 65 |
3.4.9. | Radar range equation for helicopter recognition | 66 |
3.4.10. | Helicopter recognition summary | 67 |
3.5. | Range-Doppler imaging | 67 |
3.5.1. | Introduction | 67 |
3.5.2. | Helicopter signature | 69 |
3.5.3. | Jet airliner signature | 70 |
3.5.4. | Business jet signature | 71 |
3.5.5. | Propeller aircraft signature | 72 |
3.5.6. | Waveforms and system requirements for supporting RDI | 72 |
3.5.7. | Conclusions | 73 |
3.6. | Aircraft target recognition conclusions | 73 |
| Acknowledgements | 74 |
| References | 74 |
4. | Radar ATR of maritime targets | 77 |
4.1. | Introduction | 77 |
4.2. | The use of high range resolution (HRR) profiles for ATR | 78 |
4.3. | The derivation of ATR features from HRR profiles | 80 |
4.3.1. | Length estimate | 80 |
4.3.2. | Position specific matrices (PSMs) | 83 |
4.3.2.1. | Determination of length | 83 |
4.3.2.2. | Alignment | 83 |
4.3.2.3. | Quantisation | 83 |
4.3.2.4. | Creation of reference PSMs | 84 |
4.3.2.5. | Compare the quantised test profile to the reference PSMs | 84 |
4.3.2.6. | Determine a figure of merit | 84 |
4.3.2.7. | Classification | 86 |
4.3.3. | Other examples of ATR features | 86 |
4.3.4. | Choosing sets of uncorrelated features | 87 |
4.4. | Ship ATR under the influence of multipath | 88 |
4.4.1. | What is multipath? | 88 |
4.4.2. | The problem of defining testing and training vectors | 90 |
4.5. | Results | 92 |
4.5.1. | Length estimate | 92 |
4.5.1.1. | Results for La and Lb based on measurements of ship HRR profiles | 92 |
4.5.1.2. | Simulation of ship HRR profiles | 94 |
4.5.2. | PSM results | 96 |
4.5.3. | Results based on geometrical, statistical and structural features | 99 |
4.5.3.1. | Measurements | 99 |
4.5.3.2. | Classification based on simulated ships | 104 |
4.6. | The mitigation of multipath effects on ship ATR | 107 |
4.6.1. | Using several antennas | 109 |
4.6.2. | Using several frequencies | 110 |
4.6.3. | Combining two antennas and two frequencies | 114 |
4.6.4. | Classification improvement via multi-frequency and/or multi-antenna approach | 120 |
4.7. | Summary | 123 |
| References | 125 |
5. | Effects of image quality on target recognition | 127 |
5.1. | Introduction | 127 |
5.2. | Improving ATR performance via PGA image quality enhancement | 128 |
5.3. | Improving ATR performance using high resolution, PWF-processed full-polarisation SAR data | 131 |
5.4. | Improving ATR performance via high-definition image processing | 138 |
5.5. | Reconstruction of interrupted SAR imagery | 147 |
5.6. | Summary and conclusions | 153 |
| References | 153 |
6. | Comparing classifier effectiveness | 157 |
6.1. | Introduction | 157 |
6.2. | NCTI studies | 158 |
6.3. | Measurements | 158 |
6.3.1. | TIRA system | 158 |
6.3.2. | Targets | 160 |
6.4. | Idea of classification | 160 |
6.4.1. | Appropriate features | 160 |
6.4.2. | HRR and 2D ISAR | 161 |
6.4.3. | 2D ISAR template correlation classifier | 164 |
6.4.4. | Selection of radar parameters | 166 |
6.5. | Classification scheme | 166 |
6.5.1. | Pre-processing unit | 167 |
6.5.2. | Feature extraction/reduction | 168 |
6.5.3. | Choosing a classifier | 169 |
6.5.4. | Test of classifiers | 170 |
6.6. | Feature extraction | 171 |
6.6.1. | Classification results using different feature sets | 172 |
6.7. | Conclusion | 174 |
| References | 174 |
7. | Biologically inspired and multi-perspective target recognition | 177 |
7.1. | Introduction | 177 |
7.2. | Biologically inspired NCTR | 179 |
7.2.1. | Waveform design | 179 |
7.2.2. | Nectar-feeding bats and bat-pollinated plants | 180 |
7.2.3. | Classification of flowers | 181 |
7.2.3.1. | Data collection | 182 |
7.2.3.2. | Data pre-processing and results | 182 |
7.2.4. | Classification of insects | 186 |
7.3. | Acoustic micro-Doppler | 188 |
7.3.1. | Description of the acoustic radar | 190 |
7.3.2. | Experimentation | 190 |
7.3.3. | Classification performance results | 193 |
7.4. | Multi-aspect NCTR | 194 |
7.4.1. | Data preparation | 199 |
7.4.2. | Feature extraction | 199 |
7.4.3. | Multi-perspective classifiers | 200 |
7.4.4. | Multi-perspective classification performance | 202 |
7.5. | Summary | 206 |
| References | 208 |
8. | Radar applications of compressive sensing | 213 |
8.1. | Introduction | 213 |
8.2. | Principles of compressive sensing | 214 |
8.2.1. | Sparse and compressible signals | 214 |
8.2.2. | Restricted isometric property and coherence | 216 |
8.2.3. | Signal reconstruction | 217 |
8.2.3.1. | Minimum l2 norm reconstruction | 218 |
8.2.3.2. | Minimum l0 norm reconstruction | 218 |
8.2.3.3. | Minimum l1 norm reconstruction | 218 |
8.2.3.4. | Example of l1 norm versus l2 norm reconstruction | 219 |
8.3. | Reconstruction algorithms | 220 |
8.3.1. | Convex optimisation | 220 |
8.3.1.1. | Basis pursuit | 220 |
8.3.1.2. | Basis pursuit de-noising | 221 |
8.3.1.3. | Least absolute shrinkage and selection operator | 221 |
8.3.2. | Greedy constructive algorithms | 222 |
8.3.2.1. | Matching pursuit | 222 |
8.3.2.2. | Orthogonal matching pursuit | 223 |
8.3.2.3. | Stage-wise orthogonal matching pursuit | 223 |
8.3.3. | Iterative thresholding algorithms | 224 |
8.3.3.1. | Iterative hard thresholding | 225 |
8.3.3.2. | Iterative shrinkage and thresholding | 226 |
8.4. | Jet engine modulation | 226 |
8.4.1. | Introduction | 226 |
8.4.2. | Jet engine model | 227 |
8.4.3. | Simulation results of JEM compressive sensing | 228 |
8.5. | Inverse synthetic aperture radar | 230 |
8.5.1. | Introduction | 230 |
8.5.2. | Simulation model | 231 |
8.6. | Conclusions | 234 |
| Acknowledgements | 234 |
| References | 234 |
9. | Advances in SAR change detection | 237 |
9.1. | Introduction | 237 |
9.2. | An analysis of the CCD algorithm | 239 |
9.3. | Results using the ùniversal image quality index' | 242 |
9.4. | Performance comparison of change detection algorithms | 245 |
9.4.1. | Visual comparisons of the MLE and CCD algorithms | 253 |
9.4.2. | Coherent change detection performance with shadow regions masked | 258 |
9.5. | Summary and conclusions | 263 |
| References | 263 |
10. | Future challenges | 265 |
10.1. | Introduction | 265 |
10.2. | Future challenges | 266 |
10.2.1. | Target variability and practical databases | 266 |
10.2.2. | Complex clutter environments | 267 |
10.2.3. | Use of contextual information | 268 |
10.2.4. | Performance assessment and prediction | 269 |
10.2.5. | Deception and countermeasures | 271 |
| References | 271 |
| Index | 273 |