HIRES3D HIGH RESOLUTION REMOTE SENSING FOR 3D GROUND MODELING AND - - PowerPoint PPT Presentation

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HIRES3D HIGH RESOLUTION REMOTE SENSING FOR 3D GROUND MODELING AND CLASSIFICATION Robert Hack International Institute for Geoinformation Sciences and Earth Observation (ITC) ITC Research Seminar, 3 July 2003 3 July 2003 HIRES3D - ITC

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3 July 2003 HIRES3D - ITC Research Seminar - Robert Hack 1

HIRES3D HIGH RESOLUTION REMOTE SENSING FOR 3D GROUND MODELING AND CLASSIFICATION

ITC Research Seminar, 3 July 2003

Robert Hack International Institute for Geoinformation Sciences and Earth Observation (ITC)

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3 July 2003 HIRES3D - ITC Research Seminar - Robert Hack 2

HIRES3D HIGH RESOLUTION REMOTE SENSING FOR 3D GROUND MODELING AND CLASSIFICATION

Research project in ITC’s research spearhead “Multiple use of Space” Application of Lidar

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3 July 2003 HIRES3D - ITC Research Seminar - Robert Hack 3

Lidar = LIght Detection And Ranging Laser scanning techniques give:

  • geometry
  • intensity
  • phase of reflected wave train
  • colour (if multiple different frequency lasers are

used)

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At present geometry and intensity used Geometry: spatial relation between all scanned reflection points Intensity: amount of laser energy that is reflected

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Lidar can be done from a moving or stationary system

Moving: scanning a swath; up to about 5000 reflections per second From space: until now only Space Shuttle (and weather – cloud - satellites) vertical accuracy: metres From airplane: vertical accuracy 15 – 30 cm From helicopter: vertical accuracy: order of centimetres Stationary on distance of 10’s of metres: accuracy: millimetres

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(After: USGS; http://coastal.er.usgs.gov/lidar/)

From Airplane

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(After: Puget Sound Lidar Consortium; http://duff.geology.washington.edu/data/raster/lidar/uses.htm)

Importance of accurate DEM:

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  • Spatial variation of rock and soil mass properties
  • Monitoring of topography in mountainous terrain for

stability determination of man-made slopes or man- influenced natural slopes

  • Detection of variation in subsoil properties and

monitoring of surface subsidence in coastal areas for land use and water management

In HIRES3D three applications defined for research:

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Spatial variation of rock and soil mass properties

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Objectives

Extract rock mass discontinuity information (joints, bedding planes, fractures) from high resolution “point- cloud” data derived from laser scan measurements:

Orientations Spacings Roughness

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Why ?

Discontinuities govern stability of most rock and many soil slopes, tunnels, and foundations Variation in discontinuity properties are, thus, important to design proper slopes, tunnels, and foundations

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Principle 3D laser scanning

Rapid scanning of objects

using pulsating laser

Reflection time (distance to

surface from laser) &

  • rientation of laser beam gives

position in 3D space

Dense scanning (mm to cm

resolution) yield highly accurate 3D models

Intensity of reflected pulse is

measured.

New generation of laser

scanners detect colour information as well

(After Slob et al., 2002)

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1st Approach and results

Acquisition of point cloud data of rock face

(x,y,z,intensity)

3D triangulation of points into a real 3D digital

surface

Statistic analysis of triangulated surface to obtain

the orientation of each individual triangle (dip direction/dip angle)

Plot orientations in a polar plot and create kernel

density contours to determine orientation trends

(After Slob et al., 2002)

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Rock face - Mt. Vernon (Co.), USA

(After Slob et al., 2002)

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Rock surface scan (using a Cyrax scanner

(After Slob et al., 2002)

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Visualisation of point cloud data

(After Slob et al., 2002)

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3D Delaunay triangulation to create surface through point cloud data

(After Slob et al., 2002)

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Trial on sub-dataset

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Statistic analysis of triangulated data

Kernel density pole plot

  • f all triangle orientations
  • f this part of rock surface

Digitally rendered 3d model

(After Slob et al., 2002)

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Further research (1)

Calculation of discontinuity spacing

distributions

Calculation of discontinuity surface

roughness (large- vs. small scale)

Intensity (of reflected laser beam) Geometry

Detail of interpolated discontinuity surface (appr. 50x50 cm), clearly visible are the roughness characteristics. Artificial illumination (rendering) applied to enhance relief

(After Slob et al., 2002)

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Further research (2)

Calculation of persistency of discontinuities Comparison with discontinuity information

gathered with traditional surveying:

Digital stereo photo analysis Scanline surveys

Export of rock mass discontinuity model to 3D-

GIS or numerical calculation models

(After Slob et al., 2002)

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Detection of variation in subsoil properties and monitoring of surface subsidence in coastal areas for proper land use and water management (proposal submitted for ICES3/KIS and EU-link research programs)

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Subsidence (due to peat oxidation, clay compression, weathering, water extraction, tectonic movements, etc.) and impossibility for new sediment deposits (due to, for example, dykes) in combination with (possible) rising sea water levels give more and more problems with land use and water management in coastal zones

Why ?

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Most of Western part of the Netherlands Sinking cities as Bangkok, Surabaya, Semarang, etc. Parts of Bangladesh Mexico City etc., etc.,

Examples ?

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  • Lidar monitoring data
  • 4D sub-surface model for subsidence (based on

existing geology information and Lidar monitoring data for subsidence and material compression properties)

  • 4D ground/surface water model
  • 4D geotechnical property model
  • 4D bearing capacity and settlement model for

various engineering applications

  • Decision support system for land use and water

management

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Expected:

  • higher resolution
  • cheaper equipment
  • space based scanners with high resolution

Lidar is one of the most important developments because until now no (easy and cheap) method existed to measure natural material surfaces with an accuracy anywhere near that obtained by Lidar scans

Future: