A Vertical Datum serves as a baseline for measuring elevation values, which is fundamental in geographic measurements. It provides a reference point or system against which elevations, such as sea levels or ground heights, can be compared and measured. This system allows for consistency and accuracy across various geographic regions and datasets, ensuring that all elevation data can be understood in relation to a common reference point. By using a standard vertical datum, geographers and engineers can effectively communicate and utilize elevation information for mapping, development, and planning purposes.
While the other options may relate to geographic data or measurements, they do not specifically address the purpose of a vertical datum in terms of measuring elevation. The calibration of satellite images relates more to horizontal datums and image accuracy, whereas determining longitude involves horizontal measurements rather than vertical. Spatial data adjustment protocols concern the alignment and accuracy of datasets but do not define the concept of elevation measurement itself.