Which of the following is a common datum used in geographic information systems?

The correct answer is that all of the options listed—NAD27, NAD83, and WGS84—are indeed common datums used in geographic information systems (GIS).

NAD27, or the North American Datum of 1927, was one of the early data baselines used in North America for mapping and geodesy. It was widely used in the United States and Canada for cartographic and spatial analyses particularly when accurate positional data were less easily obtained.

NAD83, the North American Datum of 1983, is an update to NAD27 and was established to provide a more accurate and uniform standard. It is based on the Global Positioning System (GPS) and is aligned with the geocentric model of the Earth, improving accuracy for modern mapping techniques.

WGS84, or the World Geodetic System of 1984, serves as the reference coordinate system for the Global Positioning System. Its global applicability makes it crucial for international applications and is widely used in various GIS and mapping technologies.

The presence of all three datums highlights their relevance and importance in the field of GIS, as different applications may require different datums depending on the spatial analysis being performed and the geographic area of focus. Understanding these