A coordinate system defines a geographical reference that you can use to specify distances for input, read positions for output, and view orientation of the model. You can place rectangular Cartesian coordinate systems or radial coordinate systems, or you can combine both radial and rectangular planes in a single coordinate system. There are two types of coordinate systems: the global coordinate system (always a rectangular Cartesian shape) and a design coordinate system (can be either shape). A design coordinate system is sometimes referred to as a plant coordinate system.