Final answer:
Clarke 1866 was selected for NaD⁺27 because it provided a good approximation of the Earth's shape in North America during the mid-20th century. However, more accurate and modern geodetic datums, like NaD⁺83, have since superseded it.
Step-by-step explanation:
The selection of Clarke 1866 for NaD⁺27 is related to the geodetic datum used for representing the shape and orientation of the Earth's surface. A geodetic datum is a set of reference points and parameters that define a coordinate system. Clarke 1866 is a geological datum that was widely used in the mid-20th century, especially in North America, as it provided a good approximation of the Earth's shape.
The selection of Clarke 1866 for NaD⁺27 is specifically related to the North American Datum of 1927 (NaD⁺27). This datum was developed for mapping and surveying applications in North America and used the Clarke 1866 ellipsoid as a reference model for the Earth's shape. By standardizing on a specific geodetic datum like Clarke 1866, geographers and surveyors were able to ensure consistency and accuracy in their measurements and calculations.
However, it's important to note that Clarke 1866 and NaD⁺27 have since been superseded by more accurate and modern geodetic datums, such as the North American Datum of 1983 (NaD⁺83) which uses the Geodetic Reference System 1980 (GRS 1980) ellipsoid. These newer datums provide a better representation of the Earth's shape and are commonly used in contemporary mapping and surveying applications.