GPR based real-time obstacle detection system for horizontal directional drilling

The paper describes the testing of an obstacle-detection radar installed on the steerable head of a Horizontal Directional Drilling (HDD) equipment; the system was developed during the ORFEUS (Operational Radar For Every drill string Under the Street) project co-funded by the European Commission under the 7 th Framework programme. HDD is a trenchless method of installing pipes and cables of various sizes, which minimizes disturbance to traffic and people living nearby. The innovative ground probing radar (GPR) based real-time obstacle detection prototype system increases the safety margins of HDD to allow its use in the widest possible range of conditions, providing indications of obstructions in the drill path so that they may be avoided. The radar is implemented using equivalent time sampling technology and integrates transmitting and receiving UWB antennas, hosted within the bore head, with beams angled forwards to provide ahead and side looking capabilities. Depending on soil conditions, it can detect obstacles at ranges further than 50 centimeters in front of and around the bore head. The radar imaging data are transmitted, in real-time, along the drill string to the surface. The hardware development consisted of the antenna design and directional sensing using 3 axes electronic gyroscope, and a communications system utilizing spread spectrum technology. A data collection and processing software suite was developed that is capable of producing a 3-D imaging output easily interpretable by the user. The sensor system was successfully demonstrated in three real operational trials, where surveys were completed resulting in the laying of new pipes and cables. Also, a power cable which was not reported in the maps was detected by the radar, so the system was halted, thus avoiding striking the object.