what is datum definition
datum. ( 1 plural: data) A measurement of something on a scale understood by both the recorder (a person or device) and the reader (another person or device). The scale is arbitrarily defined, such as from 1 to 10 by ones, 1 to 100 by 0.1, or simply true or false, on or off, yes, no, or maybe, etc.
In geology and related fields, a stratum (plural: strata) is a layer of sedimentary rock or soil, or igneous rock that were formed at the earth's surface, with internally consistent characteristics that distinguish it from other layers. The stratum is the fundamental unit in a stratigraphic column and forms the basis of the study of stratigraphy