On the Efficiency of Data Communication for the Ultramonit Corrosion Monitoring System

Abstract

Ultramonit is a system under development for permanent installation on critical parts of the subsea oil- and gas pipelines in order to monitor the corrosion continuously by using ultrasound. The communication link which connects the Ultramonit units with the outside world is identified as the system s bottleneck, and it is thus of interest to compress the ultrasonic data before transmission. The main goal of this diploma work has been to implement and optimize a lossy compression scheme in C on the available hardware (HW) with respect to a self-defined fidelity measure. Limited resources, such as memory constraints and constraints with respect to the processing time, have been a major issue during implementation. The real-time aspect of the problem results in an intricate relation between transfer time, processing time and compression ratio for a given fidelity. The encoder is optimized with respect to two different bit allocation schemes, two different filters as well as various parameters. Compared to transferring the unprocessed traces, the results demonstrate that the transfer time can be reduced with a factor 12. This yields acceptable fidelity concerning the main application of long term monitoring of subsea pipelines. However, for ultra-high precision applications where the total change in thickness due to corrosion is less than a few micrometers, compression should not be employed.