Land degradation processes characterized by airborne laser scanning – the Dead Sea as a case study

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


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



• Terminal lake

• Drains extensive

regions in the surrounding

countries

The Dead Sea



• Terminal lake

• Drains extensive

regions in the surrounding

countries

• Lowest point on earth -424 m

• High salinity level

– Unique tourist attraction

The Dead Sea



• 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



• Coastal plain widening

Receding Dead Sea Lake



Channel incision

Rapid incisiondue to exposure of steep slopes



Channel incision

• Rapid incision – 20 yrs



Dead Sea - sinkholes



• Difficulty in tracing at their early stages• Identifying subtle features

Detection and Monitoring



• Land surveying– Large span – Difficulty to trace

• Aerial images– Scale and resolution– Misinterpretation– Largely planimetric

Detection and Monitoring



Airborne laser scanning

• Detailed depiction

• Wide coverage• 3D morphometric

information

• Density 4 p/m2

• Accuracy ±10 cm



Channel Detection and Analysis



• Point cloud expression

Phenomena Expression



• Channel extraction via gradient driven analysis

Gradient based methods

x yf f 2 2x yf f



• Channel extraction via gradient driven analysis

• Ambiguous transition• Texture• Other “gradient

responding features”

Gradient based methods

x yf f 2 2x yf f



• 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



• Curvature – computation via the Hessian form

• Numerical computation


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



• 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



• Characterization via principal curvature– 1 > 0 and 2 = 0.

• Detection as hypothesis tests

• Affecting parameters– noise– surface texture


0 1 0 2

1 1 1 2

H : 0 H : 0,

H : 0 H : 0



• Ranging errors– Propagation into the eigenvalues analysis

• Hypothesis tests


26

Zmd

m

1 1 2

2 Zz md

2 12

z m

surface roughness




Eigenvalues analysis

Channel detectionLaser data



• Linkage via dynamic programming – maximum energy seeking

10 12

10

8

Eigenvalues Elevation

-400 -399

-401

-402



Tracing via energy consideration



Results



Classification



• 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



Thank You for Your Attention

Land degradation processes characterized by airborne laser scanning – the Dead Sea as a case study

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