Cost Saving Through Advanced Geophysical Classification
In 2016, GapEOD commissioned the first UltraTEM Marine system (known in Europe as the SubTEM) for the Portsmouth project. The system comprises five 1.8 m x 1.8 m transmitters loops and twenty-eight three-component sensor cubes. The system has a swath width of over 5.5 m and was designed to detect both ferrous and non-ferrous ordnance items to depths of over three meters below the sea-bottom.
The five transmitters fire sequentially while the system moves over the sea-floor at a nominal forward speed of 1 to 2 knots. Receiver data are acquired by all three-component sensor cubes from a time-range of 100 microseconds (us) to 10 milliseconds (ms) after transmitter shut-off. The conductive sea-water produces a strong background response that can mask the signals from the metallic targets of interest. However, by physical modelling of the background signal the response of metallic items can largely be isolated from that of the conductive sea-water.
The different “looks” provided by the five transmitters, coupled with the dense distribution of three component receivers allows the UltraTEM Marine to both detect and characterise buried metal. Within Portsmouth Harbour over 500 hectares were surveyed, with more than 24,000 pieces of metal identified. Advanced Geophysical Classification (AGC) allowed more than 95% of those items to be characterised as non-hazardous to the dredge operation. The remaining items were interrogated and the metal or UXO (including one torpedo and four large German bombs) were safely removed before dredging.
The reduction of targets to interrogate through AGC resulted in a huge cost saving for our client.The UltraTEM Marine system can be configured to suit a range of deployment methods and detection requirements. In 2018 the Remote Operated Vehicle (ROV) UltraTEM Marine system was commissioned. The system is 5.5 m wide when fully extended and is designed to be deployed from a Schilling Work Class ROV. The UltraTEM Marine system has application in shallow, deep, fresh and saline waters; and can be towed, pushed or deployed from stationary platforms and excavator booms.