- Laser scanning was compared to total station topographic surveys on a tunnel project in Australia.
- The derived surfaces were compared pre and post construction using the same monuments and targets.
- Laser scanning was within +/- 5 mm of the total station, and superior in terms of safety and data density.
As part of a major tunnel construction project in Melbourne, Australia digital terrain models derived from tightly controlled total station surveys were compared to laser scanning generated surfaces. Baseline surveys were conducted prior to construction and after to determine if there was any deformations from the tunnel construction. The monumentation and targeting was maintained during construction to reduce the number of unknowns and increase the level of confidence in the results.
The study concluded that the laser scanning derived surfaces were typically within +/- 5 mm for both the pre and post surveys, which was deemed to be quite acceptable. Add in the increased density of the laser scanned data, plus the improved level of safety and laser scanning came out as the superior method overall.
Comparisons of the 2 techniques reminds of the early days of GPS when they were not getting as close a check on surveyed monuments as they expected. They finally concluded that GPS was more accurate than the total station surveys. That is why, in part, that the National Geodetic Survey is no longer spending money on maintaining survey monuments.
