Doing the time warp
A long time ago, as a student, I received a phone call inviting me to crew on the Cowes-dinard race. They had just fitted an early pre-gps satellite navigation system, and as youngest crewman, and an electronics student to boot, I was assigned to be ‘satnav operator’. We completed the race across successfully without incident or distinction. We encountered the usual hazy visibility around the Channel Islands and St Malo, but the satnav, with its fixes whose accuracy depended on the availability of visible satellites, backed up our increasingly lax estimated positions. I proudly and confidently informed the rest of the crew of our exact latitude and longitude, precise to three decimal places with error ranges that were frequently less than half a mile! They were all suitably impressed.
In advance of our departure on the morning of my birthday, I carefully initialised the satnav according to the instructions to give it time to start locking on to satellites. Visibility was forecast to be moderate at best, so I didn’t want to take any chances. We passed Jersey without incident, then things started to thicken up a bit and we lost sight of land. I started plotting the satnav positions on the chart and when the cockpit sang out, ‘I think I can see land roughly due north’, I confidently predicted it to be Sark.
The lookout said it didn’t appear to be Sark, and on closer inspection (luckily not dangerously so) this turned out to be true, and we were in fact approaching Guernsey. Embarrassed, I looked for the source of the error. It turned out, as usual in navigation errors, to be a case of garbage in: garbage out.
When setting up the machine in the morning, one of the first things I did was enter the date and time. I was so used to entering my date of birth that I had inadvertently sent us back to 1963, so all of our positions were based on one wildly inaccurate piece of data. It’s a wonder that it worked at all – in fact it would have been better if it hadn’t, since then I would have probably found the error rather sooner.
I suppose I could have used the Eric Morecambe defence: ‘Listen, Sunshine – we are in exactly the right place, just not necessarily in the right decade’.