In the first category standard and reflectorless total stations are still extensively used to take profile measurements for design parameter verification and volume computations. More recently, specialized software applications have been made available that considerably automate field work and office calculations with a Compound C significant impact on operational efficiency and cost savings [8,9]. However, notwithstanding traditional surveying methods represent a flexible, precise and reliable solution to the problem they cannot provide a continuous representation of the tunnel surface. On the contrary, close range photogrammetry can provide image-based 3D models of a tunnel tube. Such models are produced using multiple images of an area suitably corrected for lens and perspective distortions [10].
For this purpose various processing techniques exist, ranging from stereoscopic vision of pair images to multi-convergent analysis supported by bundle adjustment. Nevertheless, although photogrammetric Inhibitors,Modulators,Libraries techniques offer a universal and relatively low-cost alternative, their use is less common in tunnel works due to the uneven wall surface and poor lighting conditions [11]. Also, despite the rapid advances on software tools that facilitate data collection and the processing cycle, stereoscopic plotting still requires expertise operators [10].In recent Inhibitors,Modulators,Libraries years, the emergence of laser scanning technology has opened new perspectives for the recording and 3D reconstruction of a tunnel’s wall at the various stages of a construction program.
Terrestrial Laser Scanners (TLS) use the reflection of a focused laser beam from objects to compute their location Inhibitors,Modulators,Libraries in 3D space. High resolution Inhibitors,Modulators,Libraries TLS can deliver millions of point locations with high (several millimeters to centimeter) accuracy in a short time and, in many cases, under rough field conditions. Their use in the underground space environment is suited to a wide spectrum of application areas, ranging from civil engineering [1,12], to cave modeling [13] and archaeological Entinostat documentation [10]. Section 3 provides a summary of current use of TLS in tunneling applications. From this review it is evident that despite the rapid expansion of TLS in tunneling operations, there still exists a lot of unexplored potential that, if adequately developed, would benefit greatly the tunneling industry. In effect, today, in spite of the many capabilities of TLS technology, the high cost of the equipment and the still developing algorithms for automatic data processing, along with the considerably long data acquisition times and complexity selleck chemicals llc of data management might impose some practical constraints in certain cases.