Abstract: Accurate acquisition of the in-situ status of underwater subsea pipelines and cables are the prerequisite and foundation for marine engineering installation and facility maintenance. To address the challenge in obtaining high-precision data on the in-situ parameters (e.g., position and burial depth) of buried subsea pipelines and cables during underwater engineering installation and facility maintenance operations, we used an unmanned remotely operated vehicle (ROV) guided by underwater integrated navigation as the operational platform. Equipped with a multi-beam bathymetry system and a TSS440/350 pipeline detector, the ROV enables real-time acquisition of two types of core data in deep-sea complex terrain areas: terrain data of the zones where buried pipelines/cables are located, and distance detection data from the pipeline detector. On this basis, relying on a self-developed comprehensive data processing system, a multi-sourced heterogeneous data fusion framework was constructed to achieve high-efficiency online fusion of ROV multi-dimensional data, including attitude, heading, position, and water depth. This fusion process adopts a weighted adaptive fusion algorithm to dynamically optimize the data contribution weight of each sensor, thereby effectively suppressing the cumulative error of single-sourced data and ultimately obtaining high-fidelity terrain data and in-situ status parameters of pipelines/cables. Results demonstrate that compared with traditional single-detector detection methods, the combined operation mode integrating fine detection with multi-sensor data fusion not only improves the planar position accuracy of pipelines/cables by over 30% and the burial depth accuracy by more than 25%, but also enhances operation efficiency by approximately 40%. This technology can be widely applied to pre-laying surveys, laying operations, trenching, post-burial inspections, rock-burial protection surveys, and long-term protection monitoring of subsea pipelines and cables, presenting broad application prospects in marine engineering fields.