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From sextants to Starlink: how ocean race navigation has been transformed

Home 2025 From sextants to Starlink: how ocean race navigation has been transformed

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When Adrienne Cahalan first sailed the Rolex Sydney Hobart Yacht Race back in 1984, navigation meant paper charts, dividers and a constant watch on the sky.

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“There was no GPS,” Cahalan recalls of the Cruising Yacht Club of Australia’s annual race. “I watched another navigator taking sextant sights. You really gain an appreciation for how people had to do it before digital navigation.”

Weather information came via high-frequency radio broadcasts, supplemented by experience and observation. Cloud formations were read as carefully as charts, offering clues about approaching fronts or settled high-pressure systems. Position-finding was labour-intensive, involving parallel rulers, compasses, tables and manual plotting.

That world began to change in the early 1990s with the arrival of GPS.

Adrienne Cahalan speaking at the BOM's Long Range Weather Forecast - Ashley Dart/CYCA pic.

“GPS shifted the navigator’s role,” Cahalan said. “Suddenly, you knew exactly where you were. That freed up time to focus more on tactics, boat performance and strategy.”

While location accuracy improved dramatically, weather information remained limited. Voice forecasts continued via radio, later joined by weather faxes that delivered synoptic charts on rolls of paper. The navigator still acted as the sole conduit of information on board.

The next major shift came in the early 2000s with the introduction of internet connectivity at sea, although access was heavily restricted.

“It was extremely expensive — something like $20 a megabyte,” Cahalan said. “You had to disable images and be very selective about what you downloaded.”

True real-time access did not arrive until the last few years, with the rollout of satellite broadband systems such as Starlink. For the first time, offshore crews could access the same tools available on land: live satellite imagery, radar, coastal observations and constantly updated weather models.

Cahalan is competing in the 2025 Sydney Hobart on board Aragon - Tim Wright/RORC pic.

“You can sit out there now with so many tools at your fingertips,” Cahalan said. “But they’re a guide, not a decision-maker.”

Despite the explosion of data, she argues experience and intuition remain central to navigation.

“I’ve seen these scenarios before. You watch them unfold and remember what happened last time,” she said. “That’s something technology can’t replace.”

The rise of digital tools has also changed expectations. With weather apps and online models now available to anyone, navigators face greater scrutiny.

“The expectations on navigators have gone up,” Cahalan said. “People assume you should know everything, but we don’t have a crystal ball.”

At the same time, the wider access to information has made crews more informed and engaged, reducing reliance on a single source of knowledge on board.

Some older tools have disappeared almost entirely. Sextants, once essential, are now museum pieces.

Some of the navigators in this year's Sydney Hobart (from left to right): Adrienne Cahalan, Alice Tarnawski, Chris Wild, Clare Costanzo and David Turton - Ashley Dart/CYCA pic.

“I haven’t had a sextant on a boat for 20 years,” Cahalan said. “I didn’t carry one on my last round-the-world race either.”

Paper charts, while no longer strictly necessary, still have a place.

“They’re useful as a visual reference,” she said. “People often grasp things more easily looking at a chart than at a screen.”

Modern navigation systems now resemble high-performance motorsport garages. Boats are equipped with sensors measuring speed, angle, pressure and sail shape, feeding sophisticated performance software that compares real-time data with forecast models.

“You’ve got sensors everywhere telling you what the boat is doing,” Cahalan said. “It’s incredibly computerised.”

That volume of information can be overwhelming. Knowing what to ignore has become as important as knowing what to analyse.

“You have to focus on what really matters and not chase every rabbit down a hole,” she said.

From left to right: Clare Costanzo, Alice Tarnawski, Chris Wild, David Turton and Adrienne Cahalan - Ashley Dart/CYCA pic.

Through four decades of technological change, one element has remained constant.

“Communication hasn’t changed in 40 years,” Cahalan said. “The navigator still has to clearly explain the plan — what we’re trying to achieve and how we want to sail the boat. Computers can’t do that.”

As offshore racing continues to evolve, navigation has become faster, more precise and more data-rich than ever before — but at its core, the job still relies on judgement, experience and the ability to read both the ocean and the people on board.

Steve Dettre/RSHYR media