Below is an extract from the Norie Bristol Channel Pilotage book published in 1839 - which of course does not mean the data contained therein will be anything like as up-to-date as the publication date!
The trepidation with which sailing vessels must have approached the western land mass of the UK must have been extreme in anything but fine weather given the huge leeways involved in some of the navigation tips provided!
This selection of pilotage covers an area west side of Scilly...
and makes great mention of the muddy bottom in the area - that information being hugely important to sailing ships who used a lead weight filled with tallow to help determine the nature of the bottom they were sailing over...
on the end of a line marked to indicate the depth...
today's technology allows for a level of information and accuracy that those sailors in their heavy sweaters and leather boots would be amazed...
and all displayed for the benefit of the skipper of a modern trawler in a range of wheelhouse displays...
and a muddy bottom of course means one thing only to fishermen - prawns! - and so it is we find the half dozen Scottish prawn boats currently working out of Newlyn fishing along the Jones Bank west side of Scilly - the AIS plots are based on the frequency of AIS tracks over time which now clearly show the Jones, North West and Labadie banks traditionally fished by prawn boats mainly from Brittany but increasingly by Irish vessels.