datum

noun

1. Something known or assumed as fact, and is made the basis of reasoning or inference which an intellectual system of any sort (such as knowledge or theoretical framework) is constructed.

   “a datum of experience”

   “given this datum, it follows that”

2. (form-of, singular)Singular of data: A single recorded phenomenon, especially obtained by scientific work.

   “Holonym: data set”

3. A point, line, plane, or surface with reference to which positions (such as elevations) are measured or indicated. (Examples include a permanent benchmark in leveling or mean sea level in a topographical survey).

   “A geodetic datum is sometimes also called a benchmark.”

   “GD&T tells us that the center of a bolt circle is in fact defined by the locations of the holes themselves, as each is a datum.”

   “Datums are another important map aspect related to projection. A datum provides a base reference for measuring locations on Earth's surface.”

   “For horizontal measurements [on the Earth], we fix a mathematical body of Earth in space using a Cartesian coordinate system. After that, a separate coordinate system is created over the surface of this body to generate horizontal coordinates. A mathematical earth body fixed in space makes up the horizontal datum.”

4. A floating reference point, or SLDMB, used to evaluate surface currents in a body of water, and often employed by coastal search and rescue.

verb

1. To provide missing data points by using a mathematical model to extrapolate values that are outside the range of a measuring device.

   “Removing the effects of any period of deformation by datuming or flattening selective reflection horizons should restore the structure prior to the datumed horizon, or the amount of deformation above the datumed horizon.”

   “On the left the stacking velocity functions are datumed to sea level and show great disparity.”

   “On the other hand, if we have a sufficiently accurate near-surface velocity model, we may apply wavefield datuming to convert the raw data into new data as if they were recorded along a datum below the near surface (Box 2.3).”