An Introduction To Ocean Navigation

Posted on June 2, 2014 in General

The early ocean rowers, like Harbo and Samuelsen in 1896 used sextants to navigate their courses. The challenges would have been enormous; a sextant works by measuring the angle between the horizon and a celestial body like the sun, moon or stars, so if the waves are so high that you can’t see the horizon, or if your boat is tipping so much that precise measurement is impossible, or if clouds are obscuring the skies, you’re not going to get a reliable reading.

Even once you have managed to get your reading, you then have to perform a complicated multi-step calculation, looking up figures from a book of navigation tables, and if an error creeps in at any stage of the calculation you could find yourself in a very surprising location.

Yet somehow Harbo and Samuelsen managed, as Frank Worsley would likewise succeed several years later in navigating Shackleton’s crew from Antarctica to Elephant Island across the Southern Ocean, and countless other mariners besides before the advent of the GPS (Global Positioning System) in 1995 – for which ocean rowers should be forever grateful. It is an awful lot easier to press a button and within seconds know your location to within a few metres rather than spend half an hour grappling with sextants and tables.

While rowing, most rowers will be guided by their compass, mounted within eyesight of the rowing seat. The compass will tell them which way the boat is pointing, but this may not be the direction the boat is moving in, as winds and currents may sweep the boat sideways. Checking the GPS at the end of each rowing shift will tell them if they need to modify their course.

The armchair adventurers following the Great Pacific Race will be able to monitor the crews’ progress using the map on the race website. This map uses the GPS positions sent back to Race HQ by the Yellow Brick tracking units. These have been around for a few years now, and have been tried and tested in all kinds of wilderness situations, so we’re confident that they are robust enough to survive the brutal marine environment.

In case you’re thinking that modern ocean rowers have it easy compared with the rowers of old – yes, GPS is a fantastically useful tool. But just because you know where you are, and where you want to go, doesn’t necessarily make it easy to connect the two. Our rowers will still have to confront the vagaries of ocean winds and currents. Solos are especially susceptible to Mother Nature’s whims, as there is nobody manning the oars while they sleep, compared with the pairs and fours who always have someone keeping the boat on track.

So you can expect to see lots of wiggly courses snaking their way across the Pacific towards Hawaii, like a maritime version of Whacky Races.

Compass between rowing shoes - Roz Savage