An Analysis of Supplemental Information in Contour to Grid Processing.
DEFENSE MAPPING AGENCY WASHINGTON DC
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In an effort to improve data quality and accuracy, and to increase throughput in the production of elevation matrices, Defense Mapping Agency DMA has expended considerable resources for the development and evaluation of new gridding techniques and algorithms. The algorithms reviewed have employed 1 planar, linear and weighted average interpolation techniques which offer at best a linear interpolation between features 2 surface fitting algorithms designed to approximate the earths surface between features with curve fitting techniques and 3 combinations of linear interpolation algorithms followed by filtering techniques to produce a smooth, continuous surface between features. Many of the gridding approaches evaluated are the results of attempts to reduce or eliminate the need for inclusion of supplemental geomorphic information such as drain lines and ridge lines between contours. The elimination of this type of data has potentially significant cost saving benefits, in that a major predigital compilation effort to prepare the supplemental information for digitizing would be minimized. However, in cases evaluated at DMA, the elimination or reduction of supplemental data has only served to degrade the quality and accuracy of the final elevation matrix. This paper discusses two approaches to contour-to-grid interpolation investigated at DMA and the implications of including or omitting supplemental elevation information. Discussion includes the use of supplemental data to ensure continuity at data set boundaries and the elimination of plateauing created by linear interpolation techniques.
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