3D Targets Accuracy with Leica ScanStation P20

Abstract

In particle physic accelerators survey and alignment have always been performed by means of classical geodesy instruments like theodolites, total stations, optical and electronic levels or more modern portable CMM (Coordinate Measurement Machine) arms and laser trackers. The accuracy achievable is in the order or magnitude of hundreds of µm or less depending on the scale, geometry, technics and methods used. All these instruments can collect low number of points in a limited volume. TLS (Terrestrial Laser Scanner) is a contactless measurement system and provides millions of points per second scanning rate and a full dome volume field of view. TLS accuracy is in the order of some millimetres in a range of 100m and so they do not match tight constraints for alignment; nevertheless they have possible application in the field of reverse engineering in crowded areas or whenever surfaces cannot be directly touched by a probe or difficult to reach by the operator. LBNL Engineering Division requests 3D CAD model of areas in the ALS (Advanced Light Source) particle accelerator storage ring and beam lines in which no data are available or updated. This paper investigates the registration accuracy of the TLS Leica ScanStation P20 when performing automatic targets recognition using a known network of points and multiple stations. Different types and sizes of targets have been tested.