The historical setting
Polynesian navigation or Polynesian wayfinding was used for thousands of years to enable long voyages across thousands of kilometres of the open Pacific Ocean. Polynesians made contact with nearly every island within the vast Polynesian Triangle, using outrigger canoes or double-hulled canoes. The double-hulled canoes were two large hulls, equal in length, and lashed side by side. The space between the paralleled canoes allowed for storage of food, hunting materials, and nets when embarking on long voyages. Polynesian navigators used wayfinding techniques such as the navigation by the stars, and observations of birds, ocean swells, and wind patterns, and relied on a large body of knowledge from oral tradition. This island hopping was a solution to the scarcity of useful resources, such as food, wood, water, and available land, on the small islands in the Pacific Ocean.
Navigation by the stars
The positions of the stars helped guide Polynesian voyages. Stars, as opposed to planets, hold fixed celestial positions year-round, changing only their rising time with the seasons. Each star has a specific declination, and can give a bearing for navigation as it rises or sets. Polynesian voyagers would set a heading by a star near the horizon, switching to a new one once the first rose too high. A specific sequence of stars would be memorized for each route. The Polynesians also took measurements of stellar elevation to determine their latitude. The latitudes of specific islands were also known, and the technique of "sailing down the latitude" was used.
That is, Polynesians navigated by the stars through knowledge of when particular stars, as they rotated through the night sky, would pass over the island to which the voyagers were sailing. Also knowledge that the movement of stars over different islands followed a similar pattern (that is, all the islands had a similar relationship to the night sky) provided the navigators with a sense of latitude, so that they could sail with the prevailing wind, before turning east or west to reach the island that was their destination.
Birds and ocean swells
Certain seabirds such as the white tern and noddy tern fly out to sea in the morning to hunt fish, then return to land at night. Navigators seeking land sail opposite the birds' path in the morning and with them at night, especially relying on large groups of birds, and keeping in mind changes during nesting season. Harold Gatty suggested that long-distance Polynesian voyaging followed the seasonal paths of bird migrations. In The Raft Book, a survival guide he wrote for the U.S. military during World War II, Gatty outlined various Polynesian navigation techniques for shipwrecked sailors or aviators to find land.
There are some references in their oral traditions to the flight of birds, and Gatty claimed that departing voyages used onshore range marks pointing to distant islands in line with their flight paths. A voyage from Tahiti, the Tuamotus or the Cook Islands to New Zealand might have followed the migration of the long-tailed cuckoo (Eudynamys taitensis), just as a voyage from Tahiti to Hawaii would coincide with the track of the Pacific golden plover (Pluvialis fulva) and the bristle-thighed curlew (Numenius tahitiensis). It is also believed that Polynesians, like many seafaring peoples, kept shore-sighting birds.
Re-creation of voyages
In the 1960s David Lewis sailed his catamaran from Tahiti to New Zealand, via Rarotonga using stellar navigation without instruments. Lewis sought out navigators of the Caroline Islands, Santa Cruz Islands and Tonga to confirm that traditional techniques had been retained by navigators from Polynesia, Micronesia and Melanesia. Voyages on his ketch Isbjorn included: Tevake navigating between the Santa Cruz Islands; and Hipour of Puluwat navigating in the Caroline Islands; and also conversations with Fe'iloakitau Kaho, Ve'ehala and Kaloni Kienga from Tonga; Temi Rewi of Beru and Iotiabata Ata of Tarawa in the Gilbert Islands; and Yaleilei of Satawal in the Caroline Islands.
He wrote We the Navigators in 1972 about his experiences, the title a play on the classic We the Tikopia by New Zealand anthropologist Raymond Firth, about the island of that name, whose inhabitants were gifted navigators. Ethnographic research in the Caroline Islands in Micronesia brought to light the fact that traditional stellar navigational methods were still very much in everyday use there. The building and testing of proa canoes (wa) inspired by traditional designs, the harnessing of knowledge from skilled Micronesians, as well as voyages using stellar navigation, allowed practical conclusions about the seaworthiness and handling capabilities of traditional Polynesian canoes and allowed a better understanding of the navigational methods that were likely to have been used by the Polynesians and of how they, as people, were adapted to seafaring.