Final answer:
Mean Sea Level (MSL) is the datum most often used for subsurface rights, providing a consistent reference point for measuring depths and elevations in activities such as oil and gas exploration.
Step-by-step explanation:
The datum most often used for subsurface rights, particularly in the context of oil and gas exploration, is the Mean Sea Level (MSL). This geodetic datum serves as the reference point from which depths and elevations are measured. When dealing with subsurface rights, it is crucial to have a consistent and precise datum to ensure that the legal boundaries are accurately and uniformly established.
For instance, in petroleum exploration and production, MSL is used to measure the depth of drilling boreholes and to calculate the elevation of geological features beneath the Earth's surface. This reference allows geologists, engineers, and legal professionals to have a shared understanding of where certain subsurface strata and potential resource deposits are located.