Not long after a jack-up rig called Octopus ran aground in Stronsay Firth in the Orkneys in 2006, we were feeling our way into a bay at nearby Stronsay. We crept through shoals and reefs relying on chartplotter and echo sounder, in strong winds and bad visibility, confident that our plotter would get us through: after all, we had checked it frequently on our passage up the English and Irish coasts and through the Hebrides, and had been pleasantly surprised never to find the GPS positions more than 50 metres out on the chart.
So confident had we become in our first chartplotter that a few days earlier, in fog rolling off the island of Hoy so thick that the boat’s bow was only just visible, we used it, along with the depth sounder, to find our way at dusk into the harbour of Stromness, which involves a tight turn round a reef at a point where the tide can run at up to 8 knots into Scapa Flow, right across the entrance to the inlet leading to the town.
If only we had known more about the quality of the local charts ….. much later, I came across a Marine Accident Investigations Branch report on the grounding of the jack-up rig Octopus, under tow by the tug Harald, which popped up in a web search for something else. (MAIB Report 18 2007).