A Geodesic 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 shape and size of the Earth, as well as the position of points on its surface. This system helps in accurately determining locations using coordinates, which are essential for various applications like GPS and cartography. Different types of Geodesic Datums exist, such as the WGS84 (World Geodetic System 1984), which is widely used in global positioning systems. These datums are crucial for ensuring that maps and navigation tools are consistent and reliable, allowing people to find their way accurately across the globe.