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Uncertainties introduced by the ocean surface when conducting airborne lidar bathymetry surveys

Karlsson, Torbjörn (2011) PHYM01 20112
Department of Physics
Atomic Physics
Abstract
A method for investigating how the ocean surface aects the accuracy of Airborne Lidar Bathymetry surveys, (ALB), due to environmental conditions, was developed. Computer graphic techniques were examined and utilized for construction of realistic ocean surfaces. Wave spectrum models available in the literature describing the wave number composition of ocean surfaces were used in order to be able to change the environmental conditions. Realistic ocean surface conditions for conducing ALB surveys were narrowed down and ray tracing was performed on these surfaces using thousands of rays with setups similar to those conditions. The direction for each ray was stored before and after intersecting the air/water interface. Changes in the ray... (More)
A method for investigating how the ocean surface aects the accuracy of Airborne Lidar Bathymetry surveys, (ALB), due to environmental conditions, was developed. Computer graphic techniques were examined and utilized for construction of realistic ocean surfaces. Wave spectrum models available in the literature describing the wave number composition of ocean surfaces were used in order to be able to change the environmental conditions. Realistic ocean surface conditions for conducing ALB surveys were narrowed down and ray tracing was performed on these surfaces using thousands of rays with setups similar to those conditions. The direction for each ray was stored before and after intersecting the air/water interface. Changes in the ray direction for dierent environmental conditions were studied by varying the input parameters of the wave spectrum model. Aspects that were examined include: whether there are any changes in the mean direction of the pulses, how much the mean direction of the pulses deviates from the average direction and how the footprint shape on the sea oor aects the probability of detecting targets. The result showed that wind speed, fetch size and diameter of the laser beam on the water surface all contribute to the overall accuracy of the pulse direction while the main direction of all pulses remains unchanged. The investigation technique was veried by conducting real experiments on a small scale setup while at the same time measuring the wave spectrum. Theoretical surfaces were generated, making use of the measured spectrum, and ray traced. The results were compared
showing relatively good agreement between the consecutive ray tracing and the experiments. (Less)
Please use this url to cite or link to this publication:
author
Karlsson, Torbjörn
supervisor
organization
course
PHYM01 20112
year
type
H1 - Master's Degree (One Year)
subject
language
English
id
4731166
date added to LUP
2014-10-27 17:21:33
date last changed
2014-11-04 16:57:46
@misc{4731166,
  abstract     = {A method for investigating how the ocean surface aects the accuracy of Airborne Lidar Bathymetry surveys, (ALB), due to environmental conditions, was developed. Computer graphic techniques were examined and utilized for construction of realistic ocean surfaces. Wave spectrum models available in the literature describing the wave number composition of ocean surfaces were used in order to be able to change the environmental conditions. Realistic ocean surface conditions for conducing ALB surveys were narrowed down and ray tracing was performed on these surfaces using thousands of rays with setups similar to those conditions. The direction for each ray was stored before and after intersecting the air/water interface. Changes in the ray direction for dierent environmental conditions were studied by varying the input parameters of the wave spectrum model. Aspects that were examined include: whether there are any changes in the mean direction of the pulses, how much the mean direction of the pulses deviates from the average direction and how the footprint shape on the sea oor aects the probability of detecting targets. The result showed that wind speed, fetch size and diameter of the laser beam on the water surface all contribute to the overall accuracy of the pulse direction while the main direction of all pulses remains unchanged. The investigation technique was veried by conducting real experiments on a small scale setup while at the same time measuring the wave spectrum. Theoretical surfaces were generated, making use of the measured spectrum, and ray traced. The results were compared
showing relatively good agreement between the consecutive ray tracing and the experiments.},
  author       = {Karlsson, Torbjörn},
  language     = {eng},
  note         = {Student Paper},
  title        = {Uncertainties introduced by the ocean surface when conducting airborne lidar bathymetry surveys},
  year         = {2011},
}