Airborne%20LIDAR%20(Light%20Detection%20And%20Ranging)%20at%20the%20University%20of%20Texas

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Airborne LIDAR (Light Detection And Ranging) at
the University of Texas
R. Gutierrez, J. Gibeaut, R. Smyth, T. Hepner,
J. Andrews, J. Bellian Bureau of Economic
Geology, University of Texas at Austin M.
Crawford, B. Schutz, A. Neuenschwander, J.
Trelogan, C. Weed Center for Space Research ,
University of Texas at Austin W. Gutelius and
Others Optech, Inc., Toronto
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LIDAR facts

• Pioneered by NASA Airborne Terrain
• Mapper Group
• Commercial surveys started in mid 1990s
• About 45 LIDAR groups in the world today
• Provides topographic data with 10 to 50 cm
• vertical accuracy and 1 m data point
  
• spacing

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OBJECTIVES of UT GROUP

• Apply detailed LIDAR surveys to a variety of
  research problems including
• Coastal erosion.
• Land cover classification.
• Water resource issues.
• Flood hazard prediction.
• Archaeological investigation.
• Improve analysis techniques
• Removal of vegetation and man-made structures.
• Incorporation of intensity data.
• Improve accuracy and data quality
• Develop site-specific survey procedures.
• Improve GPS accuracy.

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HOW IT WORKS

• Mirror sweeps laser beam across the ground.
• Range to target is determined by measuring time
  interval between transmission and return of
  reflected laser pulse.
• Aircraft position is determined using GPS phase
  differencing techniques.
• Pointing direction of laser determined with
  Inertial Measuring Unit (IMU) and recording of
  mirror position.
• Data streams recorded and synchronized for post
  processing.

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• Elevation accuracy 10 to 25 cm depending on
  survey height of aircraft.
• Laser pulse rate up to 25,000 per sec.
• Operating altitude 400 - 2,000 meters.
• Swath width up to 1,500 meters at 2,000 meter
  altitude.
• Records first and last returns of individual
  pulses.
• Records intensity.
• Installable in a variety of aircraft including a
  single engine Cessna 206.

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DETAILS/PROBLEMS

• Calibration
• Shadowing
• Vegetation penetration
• Long and short ranges
• Multipathing
• Ground control
• Datums

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Matagorda Peninsula
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MISSION PLANNING
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ACCURACY
Laser ranging 1 or 2 cm GPS positioning
standard deviation 5 to 7 cm GPS
positioning/system bias 0 to 40 cm IMU/scanner
mirror accuracy 0.02 degrees which means at
1,000 m AGL and at edge of 20 degree scan, error
in z 14 cm error in x,y 40 cm
Laser spot size averaging depends on terrain
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Additional LIDAR Information

• http//www.airbornelasermapping.com/ALMSkinnny.htm
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