Monitoring of directional drilling installations using 3D visualization techniques

Trenchless installation and rehabilitation methods can cause subsurface ground movements as a result of soil being removed or displaced to accommodate the new product pipe. These subsurface movements can cause damage to surface infrastructure and buried utilities resulting in significant monetary and social costs. Several municipalities and transportation agencies have started to specify detailed monitoring of their surface infrastructure for trenchless installations. Most methods specified require costly installation of surface benchmarks and crews to collect elevation data before and after the installation. After the completion of the installation, the collection of detailed as-built information is the next challenge for the agency or municipality. While log books should be the norm for most contractors, this information does not easily document where the installation is located with reference to existing topographical and utilities without bringing in a specialized survey crew. This paper presents the application of photogrammetric techniques to monitor surface movements associated with trenchless installations, and to record as built information at the completion of a horizontal directionally drilled installation. Utilizing an off the shelf consumer grade digital camera, and commercially available photogrammetry software, accurate and precise three dimensional models of the job site can be created to a levelof accuracy equal to traditional leveling techniques. Using models created from photos taken before and after an installation, changes in surface elevations can be determined in a very short time frame. At the same time, the photos can capture locates, the location of exposed utilities, and the centerline of the borepath that with information from the log book can create a three dimensional model of all utilities along the alignment. Photogrammetric methods are economical, donot utilize special equipment, and are simple to learn making them suitable to utilize as quality control tools by inspectors from municipalities and transportation agencies.