A Novel Method for Digitalisation of Test Fields by Laser Scanning

摘要： In this article, a novel, media undisruptive method for the measurement of photogrammetric test fields using a laser tracker is presented. The new approach is precise and versatile in its application. It relies on image processing on the quasi continuous measurements of a hand-held laser scanner and laser tracker combination. The field of useful applications is large. In this article, we show the benefit in the field of camera calibration. Essential for highly accurate photogrammetric measurements is a careful calibration, since all cameras have optical distortions due to manufacturing processes of the lens. The calibration can be done by e.g. using a test field. In some cases, 3D coordinates of the control points are necessary. These coordinates are often determined by photogrammetry itself and tacheometric angle measurements in advance. A scale, e.g. a subtense bar, usually needs to be included which increases the measuring efforts. The method bases on the measured 3D point cloud of a test field. With this technique, not only the centers of all control points are accessible. Other geometric features can be chosen too. Since the point cloud consist of many single point measurements, every control point determination has already a high statistical redundancy. The 3D coordinates of every single control point are extracted from the point cloud, making an additional scale obsolete. Presently, the position accuracy is ≤ 50 μm (MPE), which is mainly limited by the laser scanner used in this article. The here-presented technique can be applied to all kinds of shapes, dimensions, materials, numbers and arrangements of control points. Furthermore, it is a lot faster and easier to handle than the angle measurements of the tacheometer.