A centerline is defined from a figure. After you define the current centerline and current cross section, you can create new points in relation to them.
Before using the Inverse Point command, you must define the current centerline. If you haven't defined the centerline, you are prompted to define the centerline.
The cross section commands operate in a similar manner; if you have not set the current cross section, then you are prompted to set the cross section.
If you have not set the height of instrument and you use either the Chainage/ Offset Vertical Distance or the Chainage/Offset Staff command, then the Set Height of Instrument command is automatically invoked. Likewise, the Offset Staff or Offset Vertical Distance commands invoke the Prism command the first time you select them.