An examination of alternative compensation methods for the removal of the ridging effect from digital terrain model data files

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The province of New Brunswick began a systematic program of province-wide Digital Terrain Model (DTM) coverage in the late-1980's. Using 1:35,000-scale aearial photography, the DTMs were collected photogrammetrically as a series of profiles spaced 70 metres apart. No regard was given to breaklines along roads or water bodies. The DTMs have gone through a series of stringent quality control checks to eliminate blunders and ensure the elevations of data points are blunder-free and all fall within specified accuracy tolerances. However, users of these DTM's have continued to express concern over perceived data quality based on the evidence of a regular "ridging" effect within many of the DTM files when viewed under certain conditions. Aware of similar phenomena found in DTMs produced by other organizations, Service New Brunswick (SNB) commissioned researchers in the department of Geodesy and Geomatics Engineering at the University of New Brunswick to investigate the respective requirements and alternatives for batch processing of the DTMs to remove this ridging effect. This report presents research examining specific technical issues and compensation approaches associated with the quantification and removal of the ridging phenomena found in SNB's Enhanced Topographic Database digital terrain data. Further, the issues of ridging will be investigated from points of view ranging from a data limitation issue to a visualization issues. Finally, up to five specific solutions will be examined and compared.