Foreword ..................................................... xiii
Acknowledgments ................................................ xv
Author biography ............................................. xvii
Preface: Remote sensing of glaciers - glaciological
research using remote sensing .............................. xix
Abbreviations ............................................... xxiii
1 Principles of remote sensing ................................. 1
1.1 Background ............................................... 1
1.2 Electromagnetic radiation ................................ 2
1.3 What properties of EMR can be measured? .................. 3
1.4 Resolution ............................................... 5
1.4.1 Spatial resolution ................................. 5
1.4.2 Spectral resolution ................................ 7
1.4.3 Radiometric resolution ............................. 7
1.4.4 Temporal resolution ................................ 8
1.5 How are electromagnetic measurements converted into
information about glaciers? .............................. 9
1.6 Passive remote sensing systems ........................... 9
1.6.1 Aerial photography ................................ 10
1.6.2 Visible/near infrared scanners .................... 10
1.6.3 Thermal infrared scanners ......................... 14
1.7 Active remote sensing systems ........................... 15
1.7.1 Laser scanner (LiDAR) ............................. 15
1.7.2 Ground-penetrating radar .......................... 15
1.7.3 Synthetic Aperture Radar .......................... 16
1.8 How are data obtained? What do they cost? ............... 19
2 The formation and dynamics of glaciers ...................... 21
2.1 Introduction: How do glaciers form? ..................... 21
2.2 The climate of today's glacier environment .............. 21
2.3 Accumulation and the formation of ice ................... 25
2.4 Energy balance and ablation ............................. 26
2.5 Mass balance: Definitions and key parameters ............ 27
2.6 Ice flow ................................................ 28
2.7 Methods of mass balance determination ................... 33
2.7.1 The geodetic method ............................... 33
2.7.2 The direct glaciological method ................... 34
2.7.3 The dynamic (balance) velocity method ............. 35
2.7.4 The hydrological method ........................... 36
2.8 Debris cover and moraines ............................... 36
2.9 Conclusions ............................................. 37
3 Glacier parameters monitored using remote sensing ........... 41
3.1 Introduction ........................................... 41
3.2 Glaciers in the world .................................. 41
3.3 Reflectance and albedo ................................. 43
3.4 Surface temperature and surface melting ................ 45
3.5 Glacier zones and mass balance ......................... 48
3.5.1 Glacier zones .................................... 48
3.5.2 Glacier mass balance ............................. 51
3.5.1 Glacier area ..................................... 55
3.7 Glacier topography ..................................... 56
3.8 Bed topography and glacier volume ...................... 59
3.9 Glacier velocity ....................................... 60
3.10 Summary ................................................ 62
4 The early history of remote sensing of glaciers ............. 67
4.1 Introduction ............................................ 67
4.2 Early glacier observations .............................. 67
4.3 The scientific approach ................................. 70
4.3.1 Glacier mapping from point observations ........... 71
4.4 The dawn of photogrammetry .............................. 72
4.5 The golden age of terrestrial glacier mapping ........... 75
4.6 The aerial perspective and the step into a new age ...... 77
5 Physics of glacier remote sensing ........................... 81
5.1 Introduction ............................................ 81
5.2 Glacier ice and snow .................................... 82
5.2.1 Formation of glaciers ............................. 82
5.2.2 Glacier surface layer: snow ....................... 84
5.2.3 Glacier surface layer: ice ........................ 88
5.2.4 Glacier flow ...................................... 89
5.3 Interaction of electromagnetic radiation with ice and
snow .................................................... 90
5.3.1 General ........................................... 90
5.3.2 Optical and near infrared signals ................. 91
5.3.3 Thermal infrared signals .......................... 93
5.3.4 Microwave signals ................................. 94
5.4 Potential uses for remote sensing of glaciers ........... 95
6 Terrestrial photogrammetry in glacier studies ............... 99
6.1 The early days of terrestrial photogrammetry ........... 101
6.2 The new era or digital terrestrial photogrammetry ...... 102
6.3 Glacier DEMs from terrestrial close-range photographs:
Case study of Hintereisferner .......................... 104
6.3.1 The glacier surface as an object for
terrestrial photography ........................... 104
6.3.2 The setting and equipment ........................ 106
6.3.3 Orientations and DEM production .................. 108
6.3.4 Digital elevation models generated from
terrestrial photogrammetry ....................... 109
6.4 Prospects for terrestrial photogrammetry ............... 110
7 Aerial photogrammetry in glacier studies ................... 115
7.1 Introduction ........................................... 115
7.2 Interpretation and mapping ............................. 116
7.3 Generation of digital terrain models ................... 117
7.3.1 Analogue and analytical photogrammetry ........... 117
7.3.2 Digital photogrammetry of frame imagery .......... 118
7.3.3 Digital photogrammetry of airborne pushbroom
imagery .......................................... 120
7.4 Erors of photogrammetric DEMs .......................... 121
7.4.1 General .......................................... 121
7.4.2 Case study ....................................... 122
7.4.3 Error detection and DEM evaluation ............... 123
7.5 Vertical DEM differences ............................... 124
7.6 Lateral terrain displacements .......................... 127
7.6.1 Analogue and analytical photogrammetry ........... 127
7.6.2 Digital image matching ........................... 127
7.7 Conclusions ............................................ 131
8 Optical remote sensing of glacier extent ................... 137
8.1 Spectral properties .................................... 137
8.2 Glacier mapping and satellite sensor characteristics ... 140
8.3 Glacier mapping ........................................ 145
8.3.1 Threshold ratio images ........................... 146
8.3.2 Manual corrections ............................... 149
8.4 Conclusions ............................................ 149
9 SAR imaging of glaciers .................................... 153
9.1 Introduction ........................................... 153
9.2 SAR image formation .................................... 154
9.3 SAR interferometry ..................................... 157
9.3.1 InSAR for DEM generation ......................... 157
9.3.2 InSAR for surface displacement measurement ....... 157
9.3.3 Error contributions in InSAR observed surface
displacements .................................... 160
9.3.4 Phase noise estimation ........................... 161
9.3.5 Decorrelation sources ............................ 162
9.4 SAR backscatter from snow and ice ...................... 162
9.4.1 Backscatter modelling ............................ 164
9.4.2 First order solution ............................. 165
9.5 SAR glacier flow velocity measurements ................. 166
9.5.1 InSAR velocity ................................... 166
9.5.2 Feature tracking velocity ........................ 167
9.5.3 Speckle/coherence tracking velocity .............. 169
9.5.4 SAR glacier velocity summary ..................... 169
9.6 SAR glacier DEM ........................................ 169
9.7 SAR glacier facies detection ........................... 171
9.8 Summary ................................................ 174
10 Airborne laser scanning in glacier studies ................. 179
10.1 Measurement principles and resulting data sets ........ 179
10.2 Previous use of airborne laser scanning in
glaciological studies ................................. 182
10.3 The airborne laser scanner data sets in the OMEGA
project ............................................... 184
10.4 Application of airborne laser scanning data in
glacier studies ....................................... 186
10.4.1 Surface elevation change ....................... 186
10.4.2 Derivation of glacier velocities ............... 187
10.4.3 Surface roughness values as input for energy
balance modelling .............................. 188
10.4.4 Glacier surface classification ................. 188
10.4.5 Automatic glacier delineation and crevasse
detection ...................................... 190
10.5 Conclusions ........................................... 190
11 Ground-penetrating radar in glaciological applications ..... 195
11.1 Introduction ......................................... 195
11.2 Radio-wave propagation in glacier ice ................ 195
11.3 Radar systems ........................................ 198
11.3.1 An overview of radar systems used in
glaciology .................................... 198
11.3.2 Radar system elements ......................... 200
11.3.3 Detection and resolution ...................... 202
11.4 Operating radars on glaciers ......................... 203
11.5 Processing techniques ................................ 207
11.6 Internal structure and ice properties ................ 209
11.6.1 Internal layering ............................. 209
11.6.2 Density, water content, hydrological
aspects ....................................... 213
11.6.3 Crevasses ..................................... 216
11.6.4 Englacial channels ............................ 216
11.7 Basal properties ..................................... 216
11.7.1 Ice thickness and bedrock topography .......... 218
11.7.2 Conditions at the glacier bed ................. 218
11.8 Estimating ice volume and bed topography from ice
thickness data ....................................... 218
11.8.1 Procedure for constructing glacier surface,
ice thickness and bed topography maps and
for estimating ice volume ..................... 220
11.9 Error in ice thickness ............................... 220
11.9.1 Vertical resolution of radar data ............. 221
11.9.2 Error in thickness due to error in RWV ........ 221
11.9.3 Error in thickness associated with lack of
migration ..................................... 223
11.9.4 Surface interpolation error ................... 224
11.10 Error estimates for ice volume and bed topography
computations ......................................... 224
12 Detection and visualization of glacier area changes ........ 231
12.1 Introduction .......................................... 231
12.2 Simple image overlay .................................. 231
12.3 Orthorectification of satellite images ................ 233
12.4 GIS-based calculations ................................ 235
12.5 Visualisation of glacier change ....................... 238
12.6 Recent glacier changes in the Alps .................... 239
13 Detection of distortions in digital elevation models:
simultaneous data acquisition at Hintereisferner glacier ... 245
13.1 Introduction .......................................... 245
13.2 Related work .......................................... 246
13.3 Simultaneous data acquisition ......................... 248
13.4 Methods ............................................... 250
13.4.1 Correction of differences in georeferencing .... 250
13.4.2 Detection of distortions ....................... 251
13.5 Results ............................................... 252
13.5.1 Accuracy against ground truth data ............. 252
13.5.2 Uncertainties due to different reference
coordinate systems ............................. 256
13.5.3 Mean and RMS differences in elevation between
DEMs ........................................... 258
13.5.4 Distortions .................................... 261
13.6 Conclusions ........................................... 266
14 Accuracy aspects in topographical change detection of
glacier surface ............................................ 269
14.1 Introduction .......................................... 269
14.2 Previous research ..................................... 269
14.3 Methods for detecting and measuring changes ........... 270
14.3.1 Change in elevation ............................ 270
14.3.2 Change in volume ............................... 273
14.4 Case studies .......................................... 275
14.4.1 Aerial photography and laser scanner DEMs
over Svartisheibreen ........................... 275
14.4.2 Sequence of laser scanner DEMs over
Hintereisferner ................................ 278
14.5 Conclusions ........................................... 282
15 The role of remote sensing in worldwide glacier
monitoring ................................................. 285
15.1 Introduction .......................................... 285
15.2 The global hierarchical observing strategy ............ 285
15.3 The role of remote sensing ............................ 288
15.4 Global Land Ice Measurements from Space project and
other projects ........................................ 291
16 Conclusions ................................................ 297
Copyrights for figures ..................................... 301
Authors .................................................... 303
Reviewers .................................................. 307
Subject index .............................................. 309
Colour plates .............................................. 315
|
