Contour extraction from digital elevation models for topographical mapping with minimal information loss
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Författare
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Modellbyggare
Tidskriftstitel
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Volymtitel
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Sammanfattning
This thesis defines a measure of the amount of information lost when extracting contours
from a Digital Elevation Model (DEM). The measure is based on triangulation
of the contour vertices and Sibson’s natural neighbor interpolant Z(1). The length
of the gradients at the triangulation points are derived from the natural neighbors
defined by the triangulation itself, clamped by a minimal length. The gradient directions
are, by definition, perpendicular to the contours. As contours are used to
visualize a surface, it is important that the plot is not overly cluttered and impedes
readability. This constraint is added to the optimization problem by defining a measure
of the squiggliness of a contour. The measure is inspired by the bending force
needed to deform a thin metal rod to the shape of the contour. Different methods
are applied to the task of minimizing the information loss and contour squiggliness
and their performances are compared.
An application is created for DEM generation from Lidar data, contour extraction
and visual comparison of the extracted contours. The application aids in parameter
tuning for the tunable models. The extracted contours are also visually compared
to hand-made contours by professional orienteering mappers.
Beskrivning
Ämne/nyckelord
Contour line, isoline, topographical map, orienteering mapping