AutoCAD ordinate dimensions are used for many reasons. The main one is to decrease the amount of dimensional clutter that can result when a large number of linear dimensions are used in the view. Users are often frustrated because the placed ordinate dimensions do not relate to the model origin. In the drawing below, it obvious the ordinate dimensions are incorrect because the model is 5 units, in both X and Y directions, from the origin of the drawing.
Most users understand this but wonder how to move the origin to the required location. Some would think the best way to accomplish this is to move the model to the origin. This would work but it is often not desirable to move the model. The best way is to move and align the origin to the model. There are two AutoCAD commands that handle this task easily. If the model is aligned with the X and Y axis, use the UCS "Origin" command. In AutoCAD 2016, this command is found under the "Visualize" tab, "Coordinates" panel.