A geographic datum is a reference system used to measure and represent the Earth's surface. It provides a framework for mapping and navigation by defining the size and shape of the Earth, as well as the position of points on its surface. Common examples of geographic datums include WGS 84 and NAD 83, which are widely used in GPS technology and cartography. Geographic datums are essential for ensuring accurate location data across various applications, such as surveying, geographic information systems (GIS), and navigation. They help standardize coordinates, allowing different maps and systems to align correctly, which is crucial for effective communication and data sharing in fields like urban planning and environmental management.