National Spatial Reference System

HEIGHT SYSTEMS

DATUMS

Any surface defined as the reference surface from which heights are measured, can be called a datum

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›International Great Lakes Datum (IGLD)1955

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›Defined by one height (Father Point)

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›Water - level transfers used to connect leveling across the Great Lakes

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›Dynamic heights

oH - C/GÎ; Ge - 980.6294 gals

(Normal gravity at 45 degrees latitude as defined in 1955)