What is a datum in GIS?

A datum in GIS refers to a reference surface or model for coordinates, which is essential for accurately mapping and positioning locations on the Earth. It provides a standard framework for measuring and representing geographic locations, ensuring that spatial data is consistent and can be communicated effectively.

A datum defines how the three-dimensional surface of the Earth is projected onto a two-dimensional plane, facilitating the conversion of geographic coordinates (latitude and longitude) to a flat format suitable for mapping and analysis. Different datums exist to account for variations in the shape of the Earth, often referred to as the geoid, and can impact the accuracy of spatial data depending on the area being studied.

Understanding datums is critical for anyone working with GIS, as the choice of datum can significantly influence the precision of the spatial analysis and the integration of various data sources.