We, the Navigators, The Ancient Art of Landfinding in the Pacific is a 1972 book by the British-born New Zealand doctor David Lewis, which explains the principles of Micronesian and Polynesian navigation through his experience of placing his boat under control of several traditional navigators on long ocean voyages.
Synopsis
Introduction
David Lewis, after circumnavigating the world in a catamaran, decided to test his understanding of Polynesian navigation techniques by sailing the 2200 miles from Tahiti to New Zealand without any modern instruments (except the smallest of charts and a sky map). After arriving with a landfall only 26 miles in error, he learned that there were contemporary sailors in the Santa Cruz and Caroline Islands who still sailed large distances by the traditional methods and obtained support from the Australian National University to visit and sail with them. He did this in a 39-foot gaff ketch, Isbjorn, which he placed under the direction of the navigators Tevake and Hipour. These navigators spoke very little English, were illiterate and did not understand maps but were able to take him eventually on a 450-mile trip from Puluwat to Saipan and to return and teach him many of their techniques.
The book is largely based on these voyages, but there are extensive references to the literature.
Part 1 - The Puzzle
"Captain Cook in 1775 was uniquely fortunate in encountering Tupaia, a dispossessed high chief and navigator-priest of Raiatea who was the only highly qualified Polynesian navigator who was ever interviewed at length by Europeans." But generally the very idea that people without instruments, charts or writing, could have developed an elaborate and effective art (or "pre-science") of navigation was so utterly foreign as not even to enter the minds of most Europeans. Since then there have been the traditionalists such as Percy Smith who have uncritically accepted the migration legends of the Polynesians as literal history and those, such as Thor Heyerdahl, who dismissed these and emphasised drifting and one-way voyages.
Although the distances involved are thousands of miles, it's possible to traverse the whole ocean with voyages of not more than 310 miles with a few exceptions. The islands of the Pacific can further be grouped into "contact zones" in which the maximum distances are usually 50–200 miles. However, computer simulations have shown that pure drifting cannot explain the distribution of humans across the whole area.
Part 2 - Direction
"The most accurate direction indicators for Pacific Islanders, still used in many parts of Oceania, are stars low in the sky that have either just risen or are about to set, that is horizon or guiding stars ... Although stars rise four minutes earlier each night ... the points on the horizon where they rise and set remain the same throughout the year." Thirty-two such stars were used to form a "sidereal compass" by which directions are given (first described by José Andía y Varela in 1774). Those in the east–west direction which rise in a nearly vertical direction are the easiest to use. Other stars with the same declination must be memorised in order to continue throughout the night. In practice it is rare to require more than ten guide stars for a night's sailing—roughly twelve hours in the tropics—and fewer for an east–west course. On a cloudy night an experienced navigator can orient himself using only a few stars.
It is harder to use the sun during the day because of the changes in its position during the seasons, and it is necessary to use the swell of the ocean as an aid (not waves, which are local and variable). e.g. in the Santa Cruz group, three swells are considered to be present all round the year: the 'long swell' from the south east, the 'sea swell' from east-north-east and the 'hoahuadelahu' from the north-west. The helmsman detects the most reliable using balance.
Part 3 - Compensation and orientation
For accurate navigation it is essential to compensate for the effect of currents and leeway. Although there are usually swift currents around islands, the major currents take over more than 5–6 miles from land. The major currents are east to west in most parts of Polynesia and Micronesia, but there is a narrow band of the equatorial counter current going west to east. These can make a difference of 40 miles per day.