Introduction

One of the things that makes GIS such a powerful visualization and analytical tool is the ability to overlay multiple layers of information together in a map. Putting our GIS data in real-world coordinate systems and projections is how we are able to do this. By placing our data in a real-world system, we tie it to the Earth. This allows us to locate features anywhere on the Earth’s surface and then bring them into a map so we can see how those features are related spatially.

There are two basic types of coordinate systems we can use in ArcGIS Pro, geographic and projected. A geographic coordinate system is based on a 3D model of the earth, called the ellipsoid or spheroid. The ellipsoid is then tied back to the physical Earth by the datum. Geographic coordinate systems use degrees as their primary unit of measurement.

Each degree can then be broken down into different sub-units, such as decimal degrees, minutes, decimal minutes, or minutes, and seconds. You will often hear geographic...