When clouds hide the celestial signs, navigators use ocean swells, as well as the wind and waves, to determine their direction. Mau Piailug – grandmaster navigator around the Pacific Ocean – once said, “If you can read the ocean, you will never be lost.”

Ocean swells

Swells in the ocean are waves that persist after the wind systems or storms have died away. Swells are more regular and stable than other waves. Sometimes, swells can be felt more than seen – they can flatten out after travelling long distances.

In the Pacific, north-east trade winds generate a north-east swell, and the south-east trade winds create a south-east swell. Storms in the South Pacific during winter in the southern hemisphere generate a south swell, and storms in the North Pacific generate a north swell.

Mapping swells to the star compass

The directions from which swells come are determined by using celestial clues (the positions of the rising and setting Sun and stars). Swells move in a straight line from one house on the star compass to another house of the same name in the opposite quadrant, 180° away. For example, a swell from Manu Tokerau (north-east) will pass under a waka and head in the direction of Manu Whakarunga (south-west).

The star compass can be used as a swell compass to keep track of the movement of swells and correlate them to the rising and setting of stars.

The navigator can orientate the waka to these swells.

If you can read the ocean, you will never be lost.

Grandmaster navigator Mau Piailug

Pitching, rolling and corkscrewing – how swells affect waka

Waka move on the ocean surface in different ways, depending on how they align with swells.

Pitching

If the waka is heading Manu Marangai (south-east) with a swell coming from the south-east, the waka can be headed directly into the swell, the swell lifting the stern of the waka and pitching the waka forward.

Rolling

If the waka is travelling Manu Whakarunga (south-west), a south-east swell would roll the waka from side to side, lifting first the port hull, then the starboard hull as it passes beneath.

Corkscrewing

If the waka is heading south, the south-east swell would hit the waka at the port side at an angle of 45°, causing it to corkscrew, lifting the port bow first, then the starboard bow, then the port stern and finally the starboard stern.

The navigator becomes familiar with the motions of pitching, rolling or corkscrewing. Once the waka is oriented to the swell, the navigator can tell if there is a change of direction by the change in the waka’s motion. Navigators check the sea swell for direction at least twice a day (sunrise and sunset) – particularly as swells generated by storms can change direction because the storm is moving.

Sometimes there are several swells running. An experienced navigator can feel four or five swells at once. When the sea is not visible, these navigators can lie inside the hull of a canoe or waka and feel the motion of the swell or swells. Sometimes, at places such as doldrums, the swell pattern can be confused by waves generated by variable local winds. This is when navigating by swells alone becomes a challenge!

Wind

Wind direction can be used to hold a course – the wind is held at a constant bearing on the waka (for example, a flag flying towards the stern of the waka should remain flying in that direction to hold the same course). However, the wind may change direction and so needs to be checked with celestial clues (if they are available). Wind direction is not as stable as ocean swells.

Waves

Local and changeable winds generate waves in the ocean, which can be used to determine direction. However, wave direction changes with the wind and is not reliable for navigation.

    Published 13 November 2014