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Title: Lower Columbia and Willamette Rivers Elevation Datum Summary
Authors: Bondurant, Clifford L.
Keywords: Columbia River
Willamette River (Or.)
Data sets
Water levels
Publisher: United States. Army. Corps of Engineers. Portland District.
Abstract: This paper briefly outlines the history of the elevations systems along the Lower Columbia and Willamette Rivers as well as providing conversion tables to allow the translation of elevations from one datum to another. The Pacific Northwest has had a remarkable number of elevation datums (the set of fundamental elevations to which other elevations are referred). The numerous elevations records on the survey marks are the result of these multiple datums. A careful study of different datums reveals the geodesist’s dilemma with elevation modeling which is present in the geodetic vocabulary. The following definition is from the National Geodetic Survey (the agency responsible for our nation’s geodetic control) and illustrates this dilemma: Elevation - (1) The distance of a point above a specified surface of constant potential; the distance is measured along the direction of gravity between the point and the surface. The surface usually specified is the geoid or an approximation thereto. Mean sea level was long considered a satisfactory approximation to the geoid and therefore suitable for use as a reference surface. It is now known that mean sea level can differ from the geoid by up to a meter but the exact difference is difficult to determine. (Emphases added). [National Geodetic Survey online glossary] There will be more geodetic vocabulary (definitions) later in the report. Each of the definitions highlight the Sea Level/Geoid problem. Before adding more vocabulary, an overview is given of how elevation data is collected.
Description: Technical Report
Rights: Approved for Public Release; Distribution is Unlimited
Appears in Collections:Technical Reports

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