Abstract: A method is disclosed of measuring a hollow object such as a pipe including temporarily attaching to that object a reference target support such as a stencil that supports a plurality of scannable reference targets. When scanning the object with a movable scanner, most conveniently a hand-held scanner, the reference targets provide a positional reference for the scanner. A reference support that is attachable to or movable along a hollow object has a display face presenting and supporting a plurality of scannable reference targets. The display face can stand up from a surface of the object or can lie against a surface of the object. The reference target support and the scanner can be movable together along a pipe as an internal inspection pig.