Table of contents ............................................... I
List of figures ................................................. V
List of tables ............................................... XIII
List of acronyms ............................................... XV
List of symbols .............................................. XVII
Abstract ...................................................... XXV
Zusammenfassung ............................................. XXVII
1 Introduction ................................................. 1
1.1 Motivation .............................................. 1
1.2 State-of-the-art ........................................ 3
1.3 Scope and organization of thesis ........................ 5
2 Characterization of agricultural media with respect to
electro-magnetic scattering .................................. 9
2.1 Soil characteristics .................................... 9
2.1.1 Soil moisture ................................... 10
2.1.2 Soil roughness .................................. 13
2.2 Agricultural vegetation characteristics ................ 15
3 SAR principles and polarimetry .............................. 23
3.1 SAR principles ......................................... 23
3.1.1 Imaging geometry ................................ 23
3.1.2 Imaging resolution .............................. 25
3.1.3 Impulse response ................................ 27
3.1.4 Backscattering coefficient ...................... 28
3.1.5 Speckle reduction ............................... 29
3.2 Polarimetry ............................................ 30
3.2.1 Scattering matrix ............................... 33
3.2.2 Coherent and distributed scatterers ............. 34
3.2.2.1 Scattering vectors ..................... 34
3.2.2.2 Coherency and covariance matrix ........ 36
3.2.3 Symmetry properties ............................. 37
3.2.4. Decomposition theorems .......................... 38
3.2.4.1 Eigen-based decomposition .............. 38
3.2.4.2 Model-based decomposition ............. 43
4 Methodology of soil parameter retrieval using SAR
polarimetry ................................................. 47
4.1 Scattering models for bare soil ........................ 48
4.1.1 Empirical models ................................ 48
4.1.2 Semi-empirical models ........................... 48
4.1.3 Theoretical models .............................. 48
4.1.4 Polarimetric soil moisture inversion ............ 50
4.1.5 Polarimetric soil roughness inversion ........... 52
4.2 Scattering and decomposition models for vegetated
soils. ................................................. 54
4.2.1 Modifications of model-based decompositions ..... 55
4.2.1.1 Modification of the surface
component .............................. 56
4.2.1.2 Modification of the dihedral
component .............................. 56
4.2.1.3 Modification of the volume component ... 65
4.2.2 Separation of volume from ground components ..... 77
4.2.3 Separation of ground components using a
scattering dominance criterion .................. 81
4.2.4 Calculus of ground components ................... 86
4.2.5 Inversion for soil moisture under vegetation
cover ........................................... 87
4.2.5.1 Inversion of surface component ......... 87
4.2.5.2 Inversion of dihedral component ........ 88
4.2.5.3 Inversion of surface and dihedral
components using Pauli-based
ground-to-volume ratios ................ 89
4.2.6 Hybrid decomposition and inversion for soil
moisture under vegetation cover ................. 91
4.2.6.1 Physically constrained volume
component .............................. 93
4.2.6.2 Inversion for soil moisture ............ 94
4.2.7 Multi-angular model-based decomposition and
inversion for soil moisture under vegetation
cover ........................................... 94
4.2.7.1. Inversion for soil moisture using a
sum of absolute differences ............ 95
4.2.8. Inversion of soil roughness under vegetation
cover ... ....................................... 98
4.2.8.1. Modified X-Bragg ratio using
Pauli-based ground-to-volume ratios .... 98
5 Experimental data .......................................... 101
5.1 Study areas ........................................... 101
5.1.1 AgriSAR campaign ............................... 101
5.1.2 OPAQUE campaigns ............................... 110
5.1.3 SARTEO campaign ................................ 115
5.2 Polarimetric SAR data ................................. 117
5.2.1 Acquisition .................................... 117
5.2.2 Processing ..................................... 119
6 Results and validation of soil parameter retrieval with
experimental data .......................................... 123
6.1 Results for soil moisture ............................. 123
6.1.1 Results for soil moisture retrieval on bare
soil ........................................... 124
6.1.2 Results for soil moisture retrieval under
vegetation cover ............................... 131
6.1.2.1 Model-based decomposition ............. 132
6.1.2.2 Inversion and validation of surface
and dihedral components ............... 137
6.1.2.3 Inversion and validation of surface
and dihedral components using
Pauli-based ground-to-volume ratios ... 145
6.1.2.4 Hybrid decomposition and inversion .... 150
6.1.2.5 Multi-angular model-based
decomposition and inversion ........... 158
6.1.3 Best approach for soil moisture retrieval
under vegetation cover ......................... 166
6.2 Results for soil roughness ............................ 167
6.2.1 Results for soil roughness retrieval on bare
soil ........................................... 167
6.2.2 Results for soil roughness retrieval under
vegetation cover ............................... 170
6.2.2.1. Inversion and validation of the
modified X-Bragg ratio approach ....... 170
6.2.3. Best approach for soil roughness retrieval
under vegetation cover ......................... 172
7 Summary and conclusions .................................... 175
7.1 Summary ............................................... 175
7.2 Contributions ......................................... 182
7.3 Outlook ............................................... 183
Bibliography .................................................. 187
Appendix ...................................................... 223
A Eigen-based noise correction ............................ 223
В Growth stages of plants ................................. 224
С Volume modeling with spheroidal particles ............... 226
D Meteorological data from the AgriSAR campaign ........... 227
E Intensive measurement campaigns for soil moisture
within AgriSAR campaign ................................. 230
F Normalized Pauli-based ground-to-volume ratios .......... 231
G Surface and dihedral scattering mechanisms of the
hybrid decomposition ................................... 234
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