Multilateration with laser tracker applied in large-scale coordinate verification
Short abstract:
Modern large-scale dimensional measurement instruments such as laser trackers and iGPS typically measure the three-dimensional coordinates instead of simple lengths. Therefore verification by the measurement of lengths cannot ensure the traceability of all coordinate measurements made by the instrument. Multilateration, which combines multiple one-dimensional measurements to give three-dimensional measurements, is an optimal approach to ensure traceability of reference points to a length standard. However, several technical problems, such as the uncertainty evaluation, layout design and accuracy tests, must be solved for better performance in verification based on three-dimensional coordinates. This paper details the application of multilateration with laser trackers in establishing reference coordinates. First, a reference coordinate network is created using kinematic nests. Second, the basic principle of multilateration is reviewed. Third, the uncertainties of reference coordinates are evaluated based on the propagation of uncertainty for multivariate measurement models (GUM). Fourth, an approach of tracker layout optimization based on two-step grid-based search is studied in detail. Finally, through the repeatability test, length test, and coordinate test, it is shown that the reference coordinates satisfy their uncertainty region and can be used for coordinate verification of the large-scale measurement instruments.
