From lead lines to multibeam sonar

Lead lines produced a single depth measurement and could miss hazards immediately beside the weight. Their working depth also depended on how much rope the ship could carry and whether a windlass could recover it. After the Second World War, sonar-equipped anti-submarine escorts provided an interim pool of survey vessels while the Royal Navy retained hulls against the emerging Soviet threat. Single-beam sonar improved the process, while modern multibeam systems greatly expand both coverage and detail. More sophisticated sensors change the area a survey ship can examine in useful time as well as the accuracy of its findings. That improved picture supports navigation, submarine routes, and the placement and protection of fragile undersea data cables.