This thesis describes novel methods to localise and estimate the burial depth of subsea cables. The limitation of the current methods is that they can measure the distance to the cable only in a small vicinity, usually up to three metres. The enhancements of the methods were investigated. The output from Neural Network algorithms was tested for its ability to enlarge the detection range and increase its precision. Following traditional methods, a new approach based on system identification and modelling was inspected. Various models were proposed and enhanced with Kalman filtering for linear models and unscented Kalman filtering for nonlinear models. In the case of subsea cable tracking, Kalman filtering requires precise knowledge of the system dynamics and associated stochastic processes. These requirements are often difficult to satisfy. To overcome this limitation this thesis proposes a novel and effective algorithm based on particle filtering. The proposed novel approach uses the whole set of sample points collected from the surface above the subsea cable. The algorithm based on a batch of samples allows to eliminate effectively the noise of the readings and estimate the position of the cable from larger distances than the current methods can do. The novel batch particle filter was implemented in different applications. Depending on the survey requirements and set-up, the method can be used on a single survey line or applied to the area covered by the survey and estimate the three-dimensional section of the cable. The algorithm was tested in a simulation of tracking by an autonomous surface vehicle. Finally, the market analysis for commercialisation of the method was conducted and a new prototype was proposed. The batch particle filter was tested on experimental data collected in different locations. The results demonstrate that the method is both practical and feasible and can successfully estimate the position of the subsea cable in shallow water.

Infrastructure for electricity and telecommunication, such as subsea cables, are critical in modern society. Future estimates also indicate an increased demand. Subsea cables enable the use of offshore wind power farms, transnational energy distribution and global data transfer. It is therefore considered important for a continuous development toward a sustainable future. Consistently, long and seamless cables, with complex inner structure, are requested. This makes the manufacturing and recurrent storing process challenging. Present cable storage systems, namely carousels, are a vital part of the manufacturing.  In this case study, a present manufacturing system of subsea cables was presented, whereby a possible improvement for a more flexible manufacturing process was suggested. The work focused on developing a new turntable, which is a subsystem, within the main system, the carousel. A Systems Engineering approach was used in order to develop the manufacturing system. This development resulted in three conceptual turntable solutions with improved flexibility and resource efficiency. The solutions generated consist of a turntable with two independently rotatable compartments. Although the focus of this case study was to develop a solution toward the subsea power cable industry, it is possible to up- or downscale depending on the required weight capacity, area and number of compartments.