Therefore considering the systematic errors of measurements determined and removing them could allow providing the measurements of same accuracy (5") implementing tacheometers of lower accuracy.
Optics and optical instruments Field procedures for testing geodetic and surveying instruments --Part 5: Electronic Tacheometers.
The same principle is used in modern terrestrial laser scanners, but since a regular tacheometer is not normally intended for surface scanning applications, the scanning process is much more time consuming, though the accuracy of scanning is usually considerably higher.
Since the coordinate system in both photogrammetric and tacheometer measurements was the same (the same control points with the same coordinates were used), it was easy to match the surfaces created from the point clouds obtained by the photogrammetric and tacheometer measurements (Fig 7).
Judging from the cut section shown in figure 8, it might be stated that maximal deviation of the photogrammetricaly obtained point cloud compared to the one obtained by the tacheometer measurements does not exceed 2 mm (taking the largest area of deviations).
1" (highly dependant on linear dependant on linear reference used) reference used) Table 2 Technical specifications of the most commonly used electronic tacheometers
Instrument model Standard deviation of angle measurement Leica Leica TPS403/5/7 3", 5", 7" Leica TPS1201/2/3/5 1", 2", 3", 5" Leica TPS5000 0.
Still there can be noticed a tendency for decrease of the accuracy towards the limits of the measurements (-10[degrees] and 12[degrees]), which is quite common for the tacheometers both due to the errors of collimation at steep angles and the principle of action of vertical angle encoder of the tacheometer though more tests should be performed at that item too.
The calibration of accuracy of vertical angle measurement of Trimble 5503 tacheometer was performed using 1 m precise linear scale positioned at a distance of 2.