datumspecific

Datumspecific, sometimes written as datum-specific, refers to data, measurements, or calculations that are defined with respect to a particular geodetic datum. A geodetic datum provides a reference surface and a coordinate framework for locating points on the Earth. Data described as datum-specific are meaningful only within that reference frame; interpreting them in a different datum can cause shifts in position.

In practice, GIS, surveying, and mapping rely on datum-specific data. Examples include coordinates stated in NAD83, WGS84, or ED50, and map layers tied to a particular datum or to a time-dependent frame such as ITRF. When converting between datums, a transformation with parameters (for example a Helmert transform) is applied; without this, misalignment occurs.

Time-variant datums, such as those tied to tectonic plate movement, add complexity because coordinates drift over time. Modern practice often specifies the exact datum version (for example NAD83(2011) or WGS84). Metadata should clearly declare the datum, and any coordinate transformation used. Mixing datum references in analysis can introduce systematic errors or biases.

Related concepts include coordinate reference systems and datum shifts. For data interoperability and reproducibility, researchers and practitioners should document the datum and transformation details whenever datum-specific data are shared or analyzed.