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This guide outlines the essential procedures for conducting a Lidar survey, focusing on GPS base station operation, aircraft calibration, and preliminary data processing. Key steps include operating a minimum of two GPS base stations, merging GPS files for accurate aircraft trajectory, and maintaining optimal aircraft operations within specified parameters. Detailed methodologies for ground truth surveys and kinematic techniques are also discussed to ensure data accuracy and completeness, aiding in effective shoreline mapping and environmental monitoring.
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Section 6: Conducting the Lidar Survey
Outline • GPS base station operation • Aircraft operations mapping survey area calibration • Preliminary processing and checks for data completeness • Ground GPS data collection
GPS Base Station Operation • Minimum of two GPS base stations must be operating during the lidar survey (optimal time frame: starting 30min before takeoff running until 30min after landing of the aircraft) • Best if survey aircraft stays within 30-50km of one base station at all times • Base station and aircraft GPS files are merged to obtain a differentially corrected solution for the aircraft trajectory
ALTM system A. Laser and IMU, B. Computer/equipment rack C. Ashtech Z-12 GPS receiver. Aircraft Operations • Pilot must restrict roll (bank) angle to <15deg or you lose lock on GPS satellites and increase difficulty of obtaining a carrier phase solution for aircraft trajectory
Aircraft Operations Mapping shoreline using video camera
Aircraft Operations LANDSAT image of Bonneville Salt Flats (BSF) with orthogonal flight lines
Preliminary Processing • Preliminary processing of aircraft trajectories • Trajectories are usually accurate to within 10cm of the true position of the aircraft
Data Coverage Check Galveston, Texas West Bay Area Galveston Bay, Texas • West Bay Area
Ground Truth GPS Survey • Ground GPS surveys provide “ground truth” • Kinematic surveys conducted using same base stations as the lidar survey • Used to estimate biases in lidar data Red points are from kinematic ground GPS survey along paved road next to runway superimposed on lidar DEM
Ground GPS Survey • Methodology for conducting kinematic ground GPS surveys • Walk long distances with backpack GPS unit • Mount antenna on car roof and drive slowly up and down road many times