A height comparison test was conducted between the ScanStation 2 and the Leica TPS1200. The test was carried out on the taxiway to ensure a stable surface of uniform grade. To do this, using the EDM, two levels were taken side by side, about one metre apart, every three paces for approximately 45 metres. A scan was then done over the same area. The parameters set for the scan were 5mm horizontal by 1mm vertical at 50 metres.

The results are shown in the image below:

The effect the angle of incidence of any given target has on the accuracy of the acquisition of that particular target was studied previously by Waud (2003). This study was undertaken in a laboratory over a distance of just five metres, in conjunction with Leica Cyclone 4 software. The following research was conducted over a more practical distance of approximately 50 metres and was registered using Leica Cyclone 5.8 software.

The most interesting results in the above table are the incidence angles of 60° and 75°. It was expected that as the angle of incidence between the target and the line of sight of the scanner increased, so would the three-dimensional distance from 0°. This was not the case. Instead, the error peaked at 66mm at the incidence angle of 60° before returning to just 2mm at 75°. The source of the large error at 60° is best seen in the image below. Note the difference between the “calculated centre” and the “approx. actual centre”.



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