datum line
 基準線
 datum line
 定值線
 datum line
 x 基準線
 datum line
 y 基準線
 Da·tum n.; pl. Data
 1. Something given or admitted; a fact or principle granted; that upon which an inference or an argument is based; -- used chiefly in the plural.
    Any writer, therefore, who . . . furnishes us with data sufficient to determine the time in which he wrote.   --Priestley.
 3. pl. Math. The quantities or relations which are assumed to be given in any problem.
 Datum line Surv., the horizontal or base line, from which the heights of points are reckoned or measured, as in the plan of a railway, etc.
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