Accuracy of Stadia Tacheometry with Optical Theodolites and Levels

Five optical theodolites, Wild T16, T1, T2, Kern DKM-1, DKM-2 and one automatic level, a Wild NA2, were tested for horizontal distance and height accuracy measurement. Two cases were consi- dered. In the first, nominal values of scale factor and additive constants (K and C) were used (typically 100 and 0). In the second, these two parameters were determined in a least squares solution and applied. In the first case, the horizontal accuracy obtained ranged from ± 28 mm with the NA2 to ± 38 mm with the T16. The equivalent figures in height are ± 20 mm with the NA2 to ± 34 mm with the Wild T16. In the second case, the best results in horizontal distance accuracy was obtained with the T1 and the DKM-2 (± 24 mm), followed by the T2 (± 25 mm), the NA2 (± 26 mm), the DKM-1 (± 30 mm) and finally the T16 (±36 mm). The height accuracy also improved, the biggest improvement being obtained by the Wild T16 i.e. from ± 34 mm to ± 30 mm (i.e. 12% improvement). In both cases, however, the results obtained are much better than what is generally believed to be attainable with stadia tacheometry