The use of dual-axis laser tracking interferometer heads for quadrilateration measurements is studied and simulated. Combined with experimental trials, the results support the feasibility of a high-precision apparatus for the measurement of three-dimensional coordinates, based on a low-precision site instrumented with four double-mirror tracking heads. The definition of the laser path length follows the development and presentation of the full kinematic model of the double-mirror head. The general direct "site simulator" accounts for imperfections in the heads and can generate counts for three-dimensional grid positions. With the scanning angles unmeasured, the iterating inverse algorithm evaluates the coordinates of the grid points, while calibrating the configuration of the site together with the four count-offsets. It thus identifies all "macroscopic" instrumental unknowns, even in the context of "moving center quadrilateration", typical of dual-axis systems. The criterion used in the converging algorithm, and its sensitivity to unresolved "microscopic" imperfections in the heads, is discussed. The reconstruction of 6 × 4 × 3 m grids to better than 0.05 mm with an imperfect head assembly supports the principle that the measurement of mirror angles is not needed.
|Number of pages||17|
|Journal||Measurement: Journal of the International Measurement Confederation|
|Publication status||Published - Mar 1997|
- Dual axis
- Sensitivity analysis
- Site identification
- Tracking interferometer