83 



Video tape recordings were made of all bottom surveys to build a library of 

 the conditions. All debris was located and marked with relation to target 

 center. 



The preceeding surveying examples employed only the TV camera and depth sensor. 

 J. Westwood (1978) of the Sub Sea Surveys Ltd. describes pipe trench profiling 

 surveys that reach a higher level of sophistication in terms of data acquisition 

 and treatment. Sub Sea Survey's pipe profiling system works on the principle 

 of a high resolution echo sounder profiling the seabed below the submersible 

 and a high precision micro processor-based pressure sensor to measure the 

 vehicle's up-down motion. Data from both sensors is fed via the submersible' s 

 umbilical to a DEC PDP 11 computer. The data is programmed to remove vehicle 

 motion, plot out the shape of the pipe trench and then stored for future use. 

 In practice, the submersible is "flown" across the pipeline and a profile of 

 the pipe plotted in real time onto a plotter. The advantage of this system, 

 according to Westwood, is the absence of a "stored air" reference with all 

 its inherent drift problems. Additionally, data is available onboard in real 

 time and in a format suitable for further computer analysis. Owing to the 

 high operating frequency of the echo sounder (750kHz) and the very high 

 precision depth measurement sensor, total system accuracies of centimeters 

 are obtained. 



A further surveying application of an ROV was conducted by the National Water 

 Research Institute (formerly the Canadian Center for Inland Waters) in conjunction 

 with the Geological Survey of Canada to survey a potential under-ice pipeline 

 route for Panarctic Ltd. (Pelletier, 1977 and Roe, 1977) . The site was located 

 at a gas well in the vicinity of Drake Point on the east coast of Melville 

 Island (Lat. 77N; Long. 108W) . The pipeline route ran from 37m (120 ft) 

 water depth to shore over a seabed overlain by ice-covered waters. The 

 proposed route was 1,219m (4,000 ft) long and considered too risky for divers. 

 A 5 X 6m (16 to 20 ft) hole was cut through the ice to deploy the vehicle 

 (TROV) . Equipment on TROV included a sub-bottom profiler and a side scan sonar, 

 in addition to basic equipment such as TV, 35mm still cameras, etc. The 

 operation was conducted in temperatures of -450C and the work was conducted 

 from inside a heated work tent. A major objective was to note and chart the 

 presence of gouges in the seafloor caused by wind-driven ice dragging along 

 the bottom. Such moving masses could destroy a pipeline and possibly other 

 sea floor installations that it contacted. 



3.1.4 Diver Assistance 



While Remotely Operated Vehicles have replaced the diver in several work 

 areas, they are also significantly augmenting his work capabilities and 

 efficiency in others. Although no ROV has been specifically designed as a 

 diver assist vehicle, they are proving quite adaptable to this chore. This 

 is particularly true of the smaller vehicles, such as the RCV-225, which 

 can easily be pushed out of the way by the diver if they inadvertantly inter- 

 fere. 



Based on the current activities of- industrial firms such as Taylor Diving, 

 SESAM and Martech International, the following tasks are being conducted 

 in support of diving activities: 



