land degradation processes characterized by airborne laser scanning – the dead sea as a case study
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Mapping and Geo-Information - Technion Israel Institute of Technology
Land degradation processes characterized by airborne laser scanning – the Dead Sea as a case
study
Sagi Filin1, Smadar Morik1, Amit Baruch1, Yoav Avni2, Shmuel Marco3
1Mapping and Geo-Information Engineering, Technion – Israel Institute of Technology
2 Geological Survey of Israel3Dept. of Planetary Science, Tel Aviv University
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
• Destabilization of geomorphic systems– Climate – Anthropogenic changes
• Landscape reshaping– Environmental change – Damages existing infrastructure
• Difficult quantification• Span and complexity of these phenomenon
Dead Sea as an example
Introduction
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
• Terminal lake
• Drains extensive
regions in the surrounding
countries
The Dead Sea
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
• Terminal lake
• Drains extensive
regions in the surrounding
countries
• Lowest point on earth -424 m
• High salinity level
– Unique tourist attraction
The Dead Sea
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
• Past 40 years lake level have been dropping - 30 m from its high stand
• Increased rate in the last decade –
> 1 m/y
• Alternation of the region environment
The Dead Sea
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
• Coastal plain widening
Receding Dead Sea Lake
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
Channel incision
Rapid incisiondue to exposure of steep slopes
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
Channel incision
• Rapid incision – 20 yrs
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
Dead Sea - sinkholes
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
• Difficulty in tracing at their early stages• Identifying subtle features
Detection and Monitoring
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
• Land surveying– Large span – Difficulty to trace
• Aerial images– Scale and resolution– Misinterpretation– Largely planimetric
Detection and Monitoring
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
Airborne laser scanning
• Detailed depiction
• Wide coverage• 3D morphometric
information
• Density 4 p/m2
• Accuracy ±10 cm
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
Channel Detection and Analysis
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
• Point cloud expression
Phenomena Expression
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
• Channel extraction via gradient driven analysis
Gradient based methods
x yf f 2 2x yf f
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
• Channel extraction via gradient driven analysis
• Ambiguous transition• Texture• Other “gradient
responding features”
Gradient based methods
x yf f 2 2x yf f
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
• Surface depression as defined by curvature
• Curvature – computation via the Hessian form
Curvature based analysis
2 2
2
2 2
2
Z Zx xy
Z Zxy y
H
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
• Curvature – computation via the Hessian form
• Numerical computation
Curvature based analysis
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0 0 0
2, , ,
2 2
2, , ,
2 2
2, , , ,
2
2
2
4
y x d y x y x d
y d x y x y d x
y d x d y d x d y d x d y d x d
Z Z ZZx d
Z Z ZZy d
Z Z Z ZZxy d
2 2
2
2 2
2
Z Zx xy
Z Zxy y
H
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
• Characterization via principal curvature– 1 > 0 and 2 = 0
• Detection at multiple scales– Varying window size– Direct integration into the
numerical computation form
Channel detection via curvature
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
• Characterization via principal curvature– 1 > 0 and 2 = 0.
• Detection as hypothesis tests
• Affecting parameters– noise– surface texture
Channel detection via curvature
0 1 0 2
1 1 1 2
H : 0 H : 0,
H : 0 H : 0
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
• Ranging errors– Propagation into the eigenvalues analysis
• Hypothesis tests
Channel detection via curvature
26
Zmd
m
1 1 2
2 Zz md
2 12
z m
surface roughness
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
Curvature based analysis
Eigenvalues analysis
Channel detectionLaser data
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
• Linkage via dynamic programming – maximum energy seeking
10 12
10
8
Eigenvalues Elevation
-400 -399
-401
-402
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
Tracing via energy consideration
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
Results
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
Classification
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
• Relevance of detailed 3D morphology to landscape
reshaping studies
• Computational models for the analysis
• Feasibility of subtle features detection using airborne
platform
• Detailed characterization
Conclusions
Mapping and Geo-Information - Technion Israel Institute of Technology
Filin et al. - FIG Commissions 3 & 7 joint meeting
Thank You for Your Attention
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