LIDAR - Light Detection and Ranging

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Minnesota DOT Experiences in Testing Spatial
Sensing Technologies.
MR-RST technology exchange meeting.
April 14-15, 2003
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LIDAR Provides a Surface Model (elevations)
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LIDAR
Similar to RADAR except LIDAR utilizes light in
lieu of Radio waves.
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Bare Ground/Canopy
Source Spencer B. Gross
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Ground Elevation Model Detroit Lakes
Source Horizons, Inc.
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LIDAR super-imposed on image
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Canopy Penetration
Source Horizons, Inc.
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Introduction

• 25 projects flown using LIDAR
• Flight Height 7000 above ground level
• Swath angle 35 degrees
• Shot spacing of 4 to 14 on ground

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Costs

• Cost per acre for projects without breaklines
  added was 1.77 to 10.08.
• Cost per acre for projects with breaklines added
  was 3.29 to 10.28.
• Cost stated above may have also include
  orthophoto production).
• Project size ranged from 670 acres to 36,118
  acres.
• LIDAR project costs are greatly affected by size,
  location, terrain, land cover, manual editing -
  thinning and (ultimately) required DEM accuracy.

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LIDAR super-imposed on image
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Filtered Data
Thinned Data
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Preliminary Testing

• Some projects had detailed design mapping
  previously done in parts of the LIDAR coverage
  area.
• Two foot contours were generated from the
  detailed design TIN models and those produced
  from the LIDAR.
• The contours were overlaid on each other

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Image with stereoplotter contours
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White Stereoplotter contoursRed LIDAR
contours
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LIDAR Comparison of 2 contoursWhite -
StereoplotterRed LIDAR
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LIDAR Comparison of 2 contoursWhite -
StereoplotterRed - LIDAR
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Testing Procedure

• Requested district Surveys to obtain 20-25 random
  x,y, z coordinates in each of 5 ground cover
  types.
• Survey elevations were compared to elevations
  generated from the TIN model made from the LIDAR
  data.

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http//www.mnplan.state.mn.us/pdf/1999/lmic/nssda_
o.pdf
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NSSDA reports spatial accuracies at a 95
confidence level.
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Open Hard Surface
OHS
Range 0.29 to 1.73 Ave NSSDA 1.37
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Open Soft Surface OSS
Range 1.63 to 1.42 Ave NSSDA 0.92
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Low Ground Cover LGC
Range 4.43 to 0.72 Ave NSSDA 1.40
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High Ground Cover HGC
Range 4.13 to 2.49 Ave NSSDA 1.54
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Dense Ground Cover DGC
Range 3.12 to 2.25 Ave NSSDA 1.73
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http//www.airbornelasermapping.com/
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I will post my presentation here
http//rocky.dot.state.mn.us/Inside_LM/Photogramme
trics/Presentations/presentations.html
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For City, Township and County Folks Remember,
you may hire a contractor under the umbrella of a
State Contract.
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THANKS FOR YOUR TIME. QUESTIONS????