Chapter 7
Mapping Coastal Erosion of a Mediterranean Cliff with a Boat-Borne Laser Scanner: Performance, Processing, and Cliff Erosion Rate
Jérémy Giuliano,
Thomas J. B. Dewez,
Thomas Lebourg,
Vincent Godard,
Mélody Prémaillon,
Nathalie Marçot,
Jérémy Giuliano
GeoConseil, Risk and Geological Consulting, Le Val 83143, France
Université de Nice Sophia Antipolis, CNRS, GéoAzur UMR 7329, Observatoire de la Côte d'Azur, Valbone 06560 France
Aix-Marseille Université, CNRS CEREGE UMR 7330, Aix-en-Provence, 13545 France
Search for more papers by this authorThomas J. B. Dewez
BRGM, 45060 Orléans, 34000 Montpellier and 13009, Marseille, France
Search for more papers by this authorThomas Lebourg
Université de Nice Sophia Antipolis, CNRS, GéoAzur UMR 7329, Observatoire de la Côte d'Azur, Valbone 06560 France
Search for more papers by this authorVincent Godard
Aix-Marseille Université, CNRS CEREGE UMR 7330, Aix-en-Provence, 13545 France
Search for more papers by this authorMélody Prémaillon
BRGM, 45060 Orléans, 34000 Montpellier and 13009, Marseille, France
Search for more papers by this authorNathalie Marçot
BRGM, 45060 Orléans, 34000 Montpellier and 13009, Marseille, France
Search for more papers by this authorJérémy Giuliano,
Thomas J. B. Dewez,
Thomas Lebourg,
Vincent Godard,
Mélody Prémaillon,
Nathalie Marçot,
Jérémy Giuliano
GeoConseil, Risk and Geological Consulting, Le Val 83143, France
Université de Nice Sophia Antipolis, CNRS, GéoAzur UMR 7329, Observatoire de la Côte d'Azur, Valbone 06560 France
Aix-Marseille Université, CNRS CEREGE UMR 7330, Aix-en-Provence, 13545 France
Search for more papers by this authorThomas J. B. Dewez
BRGM, 45060 Orléans, 34000 Montpellier and 13009, Marseille, France
Search for more papers by this authorThomas Lebourg
Université de Nice Sophia Antipolis, CNRS, GéoAzur UMR 7329, Observatoire de la Côte d'Azur, Valbone 06560 France
Search for more papers by this authorVincent Godard
Aix-Marseille Université, CNRS CEREGE UMR 7330, Aix-en-Provence, 13545 France
Search for more papers by this authorMélody Prémaillon
BRGM, 45060 Orléans, 34000 Montpellier and 13009, Marseille, France
Search for more papers by this authorNathalie Marçot
BRGM, 45060 Orléans, 34000 Montpellier and 13009, Marseille, France
Search for more papers by this authorBook Editor(s):Andrea Bistacchi,
Matteo Massironi,
Sophie Viseur,
Andrea Bistacchi
Department of Environmental and Earth Sciences, University of Milano-Bicocca, Milan, Italy
Search for more papers by this authorMatteo Massironi
Department of Geosciences, University of Padua, Padua, Italy
Search for more papers by this authorSummary
Terrestrial laser scanners (TLS) are well known for providing an efficient means to monitor coastal cliff erosion. Cliffs along micro-tidal coasts, however, have often escaped quantification because the narrow or absent coastal platforms do not offer stable and embracing vantage points. To circumvent this issue, mobile laser scanning surveys from a boat can be used. We present a case study from Provence-Alpes-Côte-d'Azur (Mediterranean coast-southern France) to quantify cliff erosion in such micro-tidal environments. Three surveys were subcontracted over a period of 17 months to monitor a 3.5-km-long cliff of Carry-le-Rouet (15 km west of Marseille). Data quality was checked independently using man-made planar walls positioned above the cliff face, to retrieve survey precision and change detection thresholds. A boat-borne mobile LiDAR system was capable of describing planar features with a precision of 3–4 cm (epoch 1 and 2) and improved to 2.6 cm (epoch 3) with point densities around 100 points/m 2 . Absolute positioning accuracy varied between 0.1 cm and 0.3 cm. Because the coastline is very sinuous, we describe a method to unfold the point clouds using a continuous analytical surface made of vertical planes joined by arcs of cylinders and perform the analysis in 2.5D. Change was detected using a unique, conservative, threshold of 14 cm (99% quantile estimated on the plane change) on grids of 10 × 10 cm pixels. Integrated over the entire cliff face, the average annual cliff recession rate at Carry-le-Rouet is 1.1 cm/year. In 17 months, erosion was three times more effective in sandstone and marl layers than in calcarenites and conglomerates. Erosion varies vertically with erosion three times more effectively in the lower 25 m of the cliffs than above. Despite imperfections, boat-borne laser scanning systems are capable of delivering meaningful erosion data even in this low erosion context.
References
- Abellán , A. , Vilaplana , J.M. , and Martínez , J. ( 2006 ). Application of a long-rang e terrestrial laser scanner to a detailed rockfall study at Vall de Núria (Eastern Pyrenees, Spain) . Engineering Geology 88 ( 3–4 ): 136 – 148 .
- Abellán , A. , Calvet , J. , Vilaplana , J.M. , and Blanchard , J. ( 2010 ). Detection and spatial prediction of rockfalls by means of terrestrial laser scanner monitoring . Geomorphology 119 : 162 – 171 .
- Alho , P. , Kukko , A. , Hyyppä , H. et al. ( 2009 ). Application of boat-based laser scanning for river survey . Earth Surface Processes and Landforms 34 : 1831 – 1838 .
- Argüelles-Fraga , R. , Ordóñez , C. , García-Cortés , S. , and Roca-Pardiñas , J. ( 2013 ). Measurement planning for circular cross-section tunnels using terrestrial laser scanning . Automation in Construction 31 : 1 – 9 .
- Baltsavias , E.P. ( 1999 ). Airborne laser scanning: Basic relations and formulas . ISPRS Journal of Photogrammetry and Remote Sensing 54 : 199 – 221 .
- Barber , D. , Mills , J. , and Smith-Voysey , S. ( 2008 ). Geometric validation of a ground-based mobile laser scanning system . ISPRS Journal of Photogrammetry and Remote Sensing 63 : 128 – 141 .
- Becker , R.A. , Chambers , J.M. , and Wilks , A.R. ( 1988 ). The New S Language , Wadsworth & Brooks/Cole.
-
Bernard , T.G.
,
Lague , D.
, and
Steer , P.
(
2021
).
Beyond 2D landslide inventories and their rollover: Synoptic 3D inventories and volume from repeat LiDAR data
.
Earth Surface Dynamics
9
:
1013
–
1044
.
10.5194/esurf-9-1013-2021 Google Scholar
- Besl , P.J. and McKay , N.D. ( 1992 ). A method for registration of 3-D shapes . IEEE Transactions on Pattern Analysis and Machine Intelligence 14 ( 2 ): 239 – 256 .
- Bitelli , G. , Dubbini , M. , and Zanutta , A. ( 2004 ). Terrestrial laser scanning and digital photogrammetry techniques to monitor landslide bodies . In: Proceedings of XX ISPRS Congress (ed. O. Altan ), 246 – 251 . Turkey . Commission V, WG V/2: O.Istanbul .
- Brodu , M. and Lague , D. ( 2012 ). 3D terrestrial LiDAR data classification of complex natural scenes using a multi-scale dimensionality criterion: Application in geomorphology . ISPRS Journal of Photogrammetry and Remote Sensing 68 : 121 – 134 .
- Ciavola , P. , Armaroli , C. , Chiggiato , J. et al. ( 2007 ). Impact of storms along the coastline of Emilia-Romagna: The morphological signature on the Ravenna coastline (Italy) . Journal of Coastal Research, SI 50 : 540 – 544 .
- Collins , B. and Sitar , N. ( 2008 ). Processes of coastal bluff erosion in weakly lithified sands, Pacifica, California, USA . Geomorphology 97 ( 3 ): 483 – 501 .
-
Costa , S.
,
Delahaye , D.
,
Freiré-Diaz , S.
et al. (
2004
).
Quantification of the Normandy and Picardy chalk cliff retreat by photogrammetric analysis
. In:
Coastal Chalk Cliff Instability
, vol.
20
(ed.
R.N. Mortimore
and
A. Duperret
),
139
–
148
.
London
, Engineering Geology. Special Issue:
Geological Society
.
10.1144/GSL.ENG.2004.020.01.11 Google Scholar
-
De Guidi , G.
and
Scudero , S.
(
2013
).
Landslide susceptibility assessment in the Peloritani Mts. (Sicily, Italy) and clues for tectonic control of relief processes
.
Natural Hazard and Earth System Sciences
13
:
949
–
963
.
10.5194/nhess-13-949-2013 Google Scholar
-
Demory , F.
,
Conesa , G.
,
Oudet , J.
et al. (
2011
).
Magnetostratigraphy and paleoenvironments, in shallow-water carbonates: the Oligocene-Miocene sediments in the northern margin of the Liguro-Provençal basin (West Marseille, southeastern France)
.
Bulletin de la Société Géologique de France
182
(
1
):
37
–
55
.
10.2113/gssgfbull.182.1.37 Google Scholar
- Dewez , T.J.B. , Rohmer , J. , and Closset , L. ( 2007 ). Laser survey and mechanical modeling of chalky sea cliff collapse in Normandy, France . In: Proceedings of Landslides and Climate Change, Challenges and Solutions (ed. R. McInnes , J. Jakeways , H. Fairbanks and E. Mathie ), 281 – 288 . England : Isle of Wight .
-
Dewez , T.J.B.
,
Rohmer , J.
,
Regard , V.
, and
Cnudde , C.
(
2013
).
Probabilistic coastal cliff collapse hazard from repeated terrestrial laser surveys: Case study from Mesnil Val (Normandy, northern France)
. In:
Proceedings of the 12th International Coastal Symposium (Plymouth, England), Journal of Coastal Research
. Special Issue, vol.
65
(ed.
D. Conley
,
G. Masselink
,
P. Russel
and
T. O'Hare
),
702
–
707
.
10.2112/SI65-119.1 Google Scholar
-
Dewez , T.J.B.
,
Yart , S.
,
Thuon , Y.
et al. (
2017
).
Towards cavity-collapse hazard maps with Zeb-Revo handheld laser scanner point clouds
.
Photogram Rec.
32
:
354
–
376
. https://doi.org/10/gmfbzp.
10.1111/phor.12223 Google Scholar
- Dunning , S.A. , Massey , C.R. , and Rosser , N.J. ( 2009 ). Structural and geomorphological controls on landslides in the Bhutan Himalaya using Terrestrial Laser Scanning . Geomorphology 103 : 17 – 29 .
- Duperret , A. , Genter , A. , Mortimore , R.N. et al. ( 2002 ). Coastal rock cliff erosion by collapse at Puys, France: The role of impervious marl seams within chalk of NW Europe . Journal of Coastal Research 18 : 52 – 61 .
- Earlie , C.S. , Masselink , G. , Russell , P.E. , and Shail , R.K. ( 2014 ). Application of airborne LiDAR to investigate rates of recession in rocky coast environments . Journal of Coast Conservation 15 pp., doi: 10.1007/s11852-014-0340-1.
- Ellum , C. and El-Sheimy , N. ( 2002 ). Land-based mobile mapping systems . Photogrammetric Engineering and Remote Sensing 68 ( 1 ): 13 – 17 .
- Feldmann , B. , Lévy , C. , Dewez , T.J.B. , and Marçot , N. ( 2018 ). Méthode de comparaison de nuages de points par scanner laser mobile pour caractériser les éboulements de falaise côtières . Revue XYZ 156 : 57 – 62 .
- Furlani , S. , Pappalardo , M. , Gomez-Pujol , L. , and Chelli , A. ( 2014 ). The rock coast of the Mediterranean and Black Seas . In: Rock Coast Geomorph ology: A Global Synthesis , vol. 40 (ed. D.M. Kennedy , W.J. Stephenson and L.A. Naylor ), 89 – 123 . London Memoirs : Geological Society .
- Girardeau-Montaut , D. , Roux , M. , Marc , R. , and Thibault , G. ( 2005 ). Change detection on points cloud data acquired with a ground laser scanner . International Archives of Photogrammetry, Remote Sensing and Spatial Information Sciences 36 ( 3 ): 30 – 35 .
- Giuliano , J. ( 2015 ). Érosion des falaises de la région Provence-Alpes-Côte d'Azur:Évolution et origine de la morphologie côtière en Méditerranée: Télédétection, géochronologie, géomorphologie, PhD Thesis, Université Nice Sophia Antipolis.
- Glennie , C. , Brooks , B. , Ericksen , T. et al. ( 2013 ). Compact multipurpose mobile laser scanning system–initial tests and results . Remote Sensing 5 : 521 – 538 .
- Heritage , G. and Hetherington , D. ( 2007 ). Towards a protocol for laser scanning in fluvial geomorphology . Earth Surface Processes and Landforms 32 : 66 – 74 .
- Höhle , J. and Höhle , M. ( 2009 ). Accuracy assessment of digital elevation models by means of robust statistical methods . ISPRS Journal of Photogrammetry and Remote Sensing 64 : 398 – 406 .
- Hunter , G. , Pinkerton , H. , Airey , R. , and Calvari , S. ( 2003 ). The application of a long-range laser scanner for monitoring volcanic activity on Mount Etna . Journal of Volcanolology and Geothermal Research 123 : 203 – 210 .
- Ingensand , H. ( 2006 ). Metrological aspects in terrestrial laser-scanning technology . In: Proceedings of 3rd IAG/12th FIG Symposium (ed. A. Chrzanowski and R. Wilkins ). Germany : Baden , 22–24 May2006.
- Ingensand , H. , Ryf , A. , and Schulz , T. ( 2003 ). Performances and experiences in terrestrial lasers canning . In: Proceedings of Optical 3D-Measurement Techniques VI (ed. A. Grün and H. Kahmen ). Zurich 22–25 September 2003.
- Jaakkola , A. , Hyyppä , J. , Hyyppä , H. , and Kukko , A. ( 2008 ). Retrieval algorithms for road surface modelling using laser-based mobile mapping . Sensors 8 : 5238 – 5249 .
- Jaboyedoff , M. , Demers , D. , Locat , J. et al. ( 2009 ). Use of terrestrial laser scanning for the characterization of retrogressive landslides in sensitive clay and rotational landslides in river banks . Canadian Geotechnical Journal 46 : 1379 – 1390 .
- Jacob , T. , Samyn , K. , Bitri , A. et al. ( 2018 ). Mapping sand and clay-filled depressions on a coastal chalk clifftop using gravity and seismic tomography refraction for landslide hazard assessment, in Normandy, France . Engineering Geology 246 : 262 – 276 .
- Kemeny , J. and Post , R. ( 2003 ). Estimating three-dimensional rock discontinuity orientation from digital images of fracture traces . Computers and Geosciences 29 : 65 – 77 .
- Kuhn , D. and Prüfer , S. ( 2014 ). Coastal cliff monitoring and analysis of mass wasting processes with the application of terrestrial laser scanning: A case study of Rügen, Germany . Geomorphology 213 : 153 – 165 .
- Kukko , A. , Kaartinen , H. , Hyyppä , J. , and Chen , Y. ( 2012 ). Multiplatform mobile laser scanning: Ssability and performance . Sensors 12 : 11712 – 11733 .
- Lague , D. , Brodu , N. , and Leroux , J. ( 2013 ). Accurate 3D comparison of complex topography with terrestrial laser scanner: Application to the Rangitikei canyon (NZ) . ISPRS Journal of Photogrammetry and Remote Sensing 82 : 10 – 26 .
- Lichti , D.D. , Steward , M.P. , Tsakiri , M. , and Snow , J. ( 2000a ). Calibration and testing of a terrestrial laser scanner . International Archives of Photogrammetry, Remote Sensing and Spatial Information Sciences 33 ( B5 ): 485 – 492 .
- Lichti , D.D. , Steward , M.P. , Tsakiri , M. , and Snow , J. ( 2000b ). Benchmark tests on a three-dimensional Laser scanning system . Geomatics Research Australia 72 : 1 – 24 .
- Lim , M. , Petley , D.N. , Rosser , N.J. et al. ( 2005 ). Combined digital photogrammetry and time-of-flight laser scanning for monitoring cliff evolution . The Photogrammetric Record 20 ( 110 ): 109 – 129 .
- Lim , M. , Rosser , N.J. , Allisson , R.J. , and Petley , D.N. ( 2010 ). Erosional processes in the hard rock coastal cliffs at Staithes, North Yorkshire . Geomorphology 114 : 12 – 21 .
- López , J. and Frances , F. ( 2010 ). Influence of the North Atlantic oscillation and the Western Mediterranean oscillation in the maximum flow events in Spain . In: In International Workshop Advances in Statistical Hydrology, May 23–25, 2010 . Taormina : Italy .
-
Lopez-Saez , J.
,
Corona , C.
,
Morel , P.
et al. (
2018
).
Quantification of cliff retreat in coastal Quaternary sediments using anatomical changes in exposed tree roots
.
Earth Surface Processes and Landforms
43
:
2983
–
2997
.
10.1002/esp.4462 Google Scholar
- Marques , F.M.S.F. ( 2006 ). Rates, patterns and timing of cliff retreat. A case study on the west of Portugal . Zeitschrift für Geomorphologie-Supplementbande 144 : 231 – 257 .
-
Michoud , C.
,
Carrea , D.
,
Costa , S.
et al. (
2014
).
Landslide detection and monitoring capability of boat-based mobile laser scanning along Dieppe coastal cliffs, Normandy
.
Landslides, Technical Note.
doi:
https://doi.org/10.1007/s10346-014-0542-5
.
10.1007/s10346?014?0542?5 Google Scholar
- Millot , C. ( 1990 ). The Gulf of Lion's hydrodynamics . Continental Shelf Research 10 ( 9–11 ): 885 – 894 .
-
Monserrat , O.
and
Crosetto , M.
(
2008
).
Deformation measurement using terrestrial laser scanning data and least square 3D surface matching
.
Photogrammetric Engineering and Remote Sensing
63
:
142
–
154
.
10.1016/j.isprsjprs.2007.07.008 Google Scholar
- Murakami , H. , Nakagawa , K. , Hasegawa , H. et al. ( 1999 ). Change detection of buil dings using an airborne laser scanner . ISPRS Journal of Photogrammetry and Remote Sensing 54 : 148 – 152 .
- O'Neal , M.A. and Pizzuto , J.E. ( 2011 ). The rates and spatial patterns of annual riverbank erosion revealed through terrestrial laser-scanner surveys of the South River, Virginia . Earth Surface Processes and Landforms 36 ( 5 ): 695 – 701 .
- Olsen , M. , Johnstone , E. , Driscoll , N. et al. ( 2009 ). Terrestrial laser scanning of extended cliff sections in dynamic environments: Parameter analysis . Journal of Surveying Engineering 135 : 161 – 169 .
- Pedrazzini , A. , Oppikofer , T. , Jaboyedoff , M. et al. ( 2010 ). Assessment of rockslide and rockfall problems in an active quarry: Case study of the Arvel quarry (western Switzerland) . In: European Rock Mechanics Symposium , 593 – 596 . (EUROCK 2010), Lausanne, Switzerland : CRC Press, Leiden .
- Prémaillon , M. , Regard , V. , Dewez , T.J.B. , and Auda , Y. ( 2018 ). GlobR2C2 (Global Recession Rates of Coastal Cliffs): A global relational database to investigate coastal rocky cliff erosion rate variations . Earth Surface Dynamics 6 : 651 – 668 . https://doi.org/10/gd3hng.
- Prémaillon , M. , Dewez , T.J.B. , Regard , V. et al. ( 2021 ). Conceptual model of fracture-limited sea cliff erosion: Erosion of the seaward tilted flyschs of Socoa, Basque Country, France . Earth Surface Processes and Landforms 46 : 2690 – 2709 . https://doi.org/10/gmrc9p.
- R Core Team ( 2018 ). R: A language and environment for statistical commuting. R Foundation for Statistical Computing , Vienna, Austria . ISB 3-900051-07-0, URL http://www.R-project.org .
- Regard , V. , Dewez , T. , Bourlès , D.L. et al. ( 2012 ). Late Holocene seacliff retreat recorded by 10Be profiles across a coastal platform: Theory and example from the English Channel . Quaternary Geochronology 11 : 87 – 97 .
-
Rohmer , J.
and
Dewez , T.J.B.
(
2013
).
On the deviation of extreme sea cliff instabilities from the power law frequency volume distribution: Practical implications for coastal management
. In:
Proceedings of the 12th International Coastal Symposium (Plymouth, England), Journal of Coastal Research
. Special Issue 65 (ed.
D. Conley
,
G. Masselink
,
P. Russel
and
T. O'Hare
),
1698
–
1703
.
10.2112/SI65-287.1 Google Scholar
- Rosser , N.J. , Petley , D.N. , Lim , M. et al. ( 2005 ). Terrestrial laser scanning for monitoring the process of hard rock coastal cliff erosion . Quarterly Journal of Engineering Geology and Hydrgeology 38 : 363 – 375 .
- Rosser , N.J. , Lim , N. , Petley , D.N. et al. ( 2007 ). Patterns of precursory rockfall prior to slope failure . Journal of Geophysical Research 112 : F04014.
- Rosser , N.J. , Brain , M.J. , Petley , D.N. et al. ( 2013 ). Coastline retreat via progressive failure of rocky coastal cliffs . Geology 41 : 939 – 942 .
- Sabatier , P. , Samat , O. , Ullmann , A. , and Suanez , S. ( 2009 ). Connecting large-scale coastal behaviour with coastal management of the Rhône delta . Geomorphology 107 : 79 – 89 .
- Schwarz , K.P. , Chapman , M.A. , Cannon , M.W. , and Gong , P. ( 1993 ). An integrated INS/GPS approach to the georeferencing of remotely-sensed sata . Photogrammetric Engineering and Remote Sensing 59 ( 11 ): 1667 – 1674 .
- Soudarissanane , S. , Lindenbergh , R. , Menenti , M. , and Teunissen , P. ( 2011 ). Scanning geometry: Influencing factor on the quality of terrestrial laser scanning points . ISPRS Journal of Photogrammetry and Remote Sensing 66 : 389 – 399 .
- Stepp , J.C. ( 1972 ). Analysis of completeness of the earthquake sample in the Puget Sound area and its effect on statistical estimates of earthquake hazard . In: Proceedings of the First Microzonation Conference , 897 – 909 . Seattle, USA .
- Stock , G.M. , Bawden , G.W. , Green , J.K. et al. ( 2011 ). High-resolution three-dimensional imaging and analysis of rock falls in Yosemite Valley, California . Geosphere 7 ( 2 ): 573 – 581 .
- Teza , G. , Galgaro , A. , Zaltron , N. , and Genevois , R. ( 2007 ). Terrestrial laser scanner to detect landslide displacement fields: a new approach . International Journal of Remote Sensing 28 : 3425 – 3446 .
- Vaaja , M. , Hyyppä , J. , Kukko , A. et al. ( 2011 ). Mapping topography changes and elevation accuracies using a mobile laser scanner . Remote Sensing 3 : 587 – 600 .
- Vaaja , M. , Kukko , A. , Kaartinen , H. et al. ( 2013 ). Data processing and quality evaluation of a boat-based mobile laser scanning system . Sensors 13 : 12497 – 12515 .
- van Westen , C. ( 1997 ). Statistical landslide hazard analysis, Application guide, ILWIS 2.1 for Windows . ITC, Enschede , The Netherlands .
- Vögtle , T. and Steinle , E. ( 2004 ). Detection and recognition of changes in building geometry derived from multitemporal laser scanning data . International Archives of Photogrammetry, Remote Sensing and Spatial Information Sciences 35 ( B2 ): 428 – 433 .
- Vosselman , G. , Gorte , B.G.H. , and Sithol , G. ( 2004 ). Change detection for updating medium scale maps using laser altimetry . International Archives of Photogrammetry, Remote Sensing and Spatial Information Sciences 35 ( B3 ): 207 – 212 .
- Young , A.P. and Ashford , S.A. ( 2006 ). Application of airborne LIDAR for seacliff volumetric change and beach sediment contributions . Journal of Coast al Research 22 : 307 – 318 .
- Young , A.P. and Ashford , S.A. ( 2007 ). Quantifying sub-regional seacliff erosion using mobile terrestrial LiDAR . Shore Beach 75 : 38 – 43 .
- Young , A.P. , Flick , R.E. , Gutierrez , R. , and Guza , R.T. ( 2009 ). Comparison of short-term seacliff retreat measurement methods in Del Mar, California . Geomorphology 112 : 318 – 323 .
- Young , A.P. , Olsen , M.J. , Driscoll , N. et al. ( 2010 ). Comparison of airborne and terrestrial LIDAR estimates of seacliff erosion in southern California . Photogrammetric Engineering and Remote Sensing 76 : 421 – 427 .
