This purpose for external geometry sets up ‘check’ objects (distances or points) in the Imports and Coordinate Systems Pane. Check points represent known x,y,z point locations that you wish to compare with points in the project, while check distances represent known distances you wish to compare with the measurements between two points (or a line) in the project. These ‘check’ objects do not affect the coordinate system, are not used as control, and are not 3d objects that appear in the 3D Viewer – their purpose is QA / quality assurance. See Check distances and Check points. See also Add new empty object.