Which reference ellipsoid is associated with North American Datum 1983?

The reference ellipsoid associated with the North American Datum 1983 (NAD83) is the Geodetic Reference System 1980 (GRS80). NAD83 was developed to provide a consistent and accurate framework for geospatial data across North America, and GRS80 serves as its underlying mathematical model of the Earth's shape and size.

GRS80 is a geodetic reference system that modelizes the Earth's surface as an ellipsoid, and it was designed to be aligned with the Earth's gravity field to improve positional accuracy. This ellipsoid is based on modern measurements and incorporates advances in geodesy, making it suitable for precise mapping and positioning tasks.

In contrast, other options such as Clarke 1866, WGS84, and Geodetic Reference System 1966 serve different purposes or are used in other datums and applications. While WGS84 is used globally and is compatible with GPS technology, it is not the reference ellipsoid for NAD83. This association between NAD83 and GRS80 is fundamental in the field of GIS, ensuring coherence in spatial data across various applications and technologies.