What is the preferred spheroid used in the United States?

The preferred spheroid used in the United States is GRS 1980, which stands for the Geodetic Reference System 1980. This spheroid was specifically designed to provide a better approximation of the Earth's shape for geodetic applications in North America. The GRS 1980 spheroid is widely utilized in the National Spatial Reference System (NSRS) and is the basis for the horizontal control of GPS systems used in mapping, surveying, and various other applications.

The GRS 1980 spheroid improves upon earlier models by offering a more accurate representation of the Earth's geoid and physical dimensions, which accommodate the country's diverse topography. This accuracy is vital for work requiring precise measurements, such as civil engineering, land use planning, and natural resource management.

While WGS 1984 is commonly used globally for GPS purposes, it does not specifically cater to the geographical nuances of the U.S., making GRS 1980 the preferred choice within the United States. The International 1924 and GRS 1967 spheroids are older models and have largely been replaced by the more accurate GRS 1980 in contemporary applications.