What is the current datum used for projected coordinate systems in the United States?

The current datum used for projected coordinate systems in the United States is NAD83 (North American Datum of 1983). This geodetic datum provides a consistent frame of reference for mapping and spatial data across North America, allowing for improved accuracy in various applications, including GIS.

NAD83 is based on a modern approach to the Earth’s shape and size through satellite technology, making it more accurate than its predecessor, NAD27, which was based on older survey methods. The introduction of NAD83 marked a significant advancement in spatial reference systems, enabling better interoperability between various mapping and geographic systems.

While WGS84 is a widely used global datum, especially in GPS technology, NAD83 is specifically tailored for North America, and hence it remains the preferred choice for most mapping projects within the United States. The other options, such as NAD27 and NAD92, either represent older datums or have been superseded by NAD83 for general use, reflecting the ongoing advancements in geospatial sciences. Thus, NAD83 is recognized as the standard datum for projected coordinate systems in current practice.