References

1. Navigation and the Natural Environment: the 2007 Voyage to Micronesia and Japan at http://pvs.kcc.hawaii.edu/2007voyage/2007navigation.html

2. For an explanation of the techniques used to navigate Hokule’a and Maisu without instruments, see http://pvs.kcc.hawaii.edu/L2wayfind.html .

3. For the Hawaiian star compass used by the navigators, see http://pvs.kcc.hawaii.edu/2007voyage/2007starcompass.html .

Navigational Plan to Majuro

As crew member Ka’iulani Murphy notes in her Jan. 24 report from Hokule’a, the navigational plan is to head “‘Aina Kona (WSW), … until we get to 17 degrees N, then sail Komohana (W) until we see Johnston Island.”

This island will provide a locational marker in the open sea. From Johnston, the navigators can set a more exact course for Majuro, which lies 1262 nautical miles (2337 km) from Johnston, bearing 245 degrees, ‘Aina Kona (WSW).

Expanded Landfall

Navigator Nainoa Thompson notes in the January 22 press release (“Hokule'a and Alingano Maisu On Their Way”) “finding Johnston is like finding a needle in a hay stack. It is so small and so low and there are not many trees. The navigators will be heavily relying on certain seabirds that inhabit that atoll.”

The birds the navigators rely on for land-finding are the noio (noddy tern) and manu o ku (white tern). These birds fly out from an island to fish in the morning, and return to the island at night. The range of the noio is generally 40 miles from an island; the range of the manu o ku is 120 miles. (For photos of the birds and an explanation of other landfinding techniques, see http://pvs.kcc.hawaii.edu/navigate/land.html .)

So when looking for islands, the navigators look for terns at sunrise and sunset. If they sight them at sunrise, the island is in the direction the birds are flying from; if they sight them at sunset, the island is in the direction the birds are flying to.

Johnston Atoll is less than 2 miles long and 1 mile wide. Sighting birds that nest on it can expand the island’s presence to an area as large as 240 miles in diameter. Nainoa calls the range of birds around an island "the circle of birds."(For a photo of the island and information on birds and other wildlife of Johnston Atoll, see http://www.fws.gov/pacificislands/wnwr/pjohnsnwr.html .)

The flight-path of birds other than terns are less useful as clues to the direction of land, as they may stay in the air or on the ocean for longer periods than a day; some seabirds spend most of their lives at sea.)

Should the navigators not sight Johnston Atoll when they think they are in the vicinity, they may choose to search for it (sailing in a zigzag pattern) or continue on to Majuro without sighting it. (Wayfinding without instruments involves a strategy for getting to a destination in ever-changing wind and weather conditions, rather than the certainty of arriving at a specific place at a precise time. The canoes can only sail in the directions and at the speeds the winds allow them to. And while those of us following the voyage on the web know exactly where the canoes are through GPS signals, the navigators and crews don’t. They know the vicinities or directions of islands, based on their estimates of distances and directions traveled and readings of celestial, atmospheric, and oceanic clues.)

Majuro is part of a chain of relatively closely spaced atolls, the Marshall Islands, stretching about 10 degrees, or 600 nautical miles, southeast to northwest, in the direction of ‘Aina Kona (WSW) from Hawai’i and Johnston Atoll. Map of the Marshall Islands: http://www.rmiembassyus.org/Geography.htm .

Whether the canoes sight Johnston or not, the canoes plan to sail WSW from the vicinity of Johnston and intersect the Marshall Islands chain at some point near the latitude of Majuro, using latitude stars (see "Celestial Bodies: Latitude Clues" below) and observations of the flight path of seabirds to find an island. (Each atoll in the chain is greatly expanded in its presence by the populations of terns on the islands.)

Nainoa notes about the Marshalls chain: "The Marshall Islands is a whole nest of islands, not a single island like Johnston Atoll. The islands are heavily wooded primarily with coconut trees and the population of seabirds is very large. One of the difficulties is because there are so many islands, the birds are sometimes hard to read, because they fly to and from the islands from multiple directions."

The closer to Majuro the canoes are when they intersect the chain, the less inter-island sailing they will have to do to get there.

Celestial Bodies: Holding a Course

The navigators use celestial bodies (sun and moon; Hokupa’a, or the North Star; Hokuloa, or Venus, etc.) to guide the canoes.

When celestial bodies are near the horizon as they rise and set, they provide temporary directional markers. For example, the sun at this time of the year rises in ‘Aina Malanai (ESE) and sets in ‘Aina Kona (WSW). (The rising and setting points of the sun will move slowly northward each day, until at the spring equinox on March 22, the sun will rise exactly Hikina, or E, and set exactly Komohana, or W).

If the navigators want to head WSW at this time of the year, they can head directly at the sun while it is setting.

Hokuloa (Venus) follows the sun down to the horizon an hour and a half after the sun sets. Hokuloa sets in the directional house of La Kona (W by S). To hold a course WSW, the setting Hokuloa is lined up one directional house (11.25 degrees) to the starboard (right) of the bow.

The moon also rises in the east and sets in the west, though the rising and setting points move each night and the times it rises and sets change. When the moon rises in the daytime and is visible, it’s a directional clue at a time when no other celestial bodies are available.

At night, Hokupa’a, the North Star, which is located near the celestial north pole and thus doesn’t rise or set in the northern hemisphere, appears stationary due north. To hold a course due west, the navigator would keep this star directly off the starboard (right) side of the canoe. To hold a course WSW by Hokupa’a, the star would be two houses back of starboard.

The navigators may use a whole range of stars as directional clues, depending on the time of the year.

Currently, for example, Hokule’a (Arcturus) rises at about 11 p.m. in the direction of ‘Aina Ko’olau (ENE). ‘A’a (Sirius) sets at about 3 p.m in the direction of ‘Aina Kona (WSW).

See the following webpage for the rising points of the brightest, most visible stars in the sky: http://pvs.kcc.hawaii.edu/navigate/BrightStars.html . (The setting points are in the same houses as the rising points, but on the opposite side of the sky, the stars rising in the NE quadrant of Ko'olau setting in the NW quadrant Ho'olua, and the stars rising in the SE quadrant of Malanai setting in the SW quadrant of Kona.)

Celestial Bodies: Latitude Clues

The navigational plan involves sailing west toward Johnston at 17 degrees N. To estimate latitude, the navigators observe the altitude of stars crossing the meridian (an imaginary line that arches overhead on the celestial dome from due north to due south) as the stars journey from east to west across the night sky. The navigator measures the altitude of celestial bodies with his outstretched hand, different parts of his hand calibrated to different altitudes.

The altitude of Hokupa’a, on the meridian above due north, is a clue to latitude: at 17 degrees N, it’s 17 degrees above the horizon.

Hanaiakamalama, the Southern Cross, which appears upright early in the morning before sunrise, is both a directional and a latitude clue. It points due south. Its altitude as it transits the meridian is also a clue to latitude: at 17 degrees N, it’s 9 degrees above the horizon, 3 degrees higher than at 20 degrees N in Hawai'i.

Also at 17 degrees N, Miaplacidus, in the constellation Carina, transits the meridian after midnight above due south, at 3 degrees, aligning perpendicularly to the horizon with the stars Turais and Suhail directly above it. (See the Hokule'a Crew Report for Jan. 28.)

Navigating by the Ocean Swells

At sunrise and sunset, the navigators orient the canoes to the rising and setting sun and determine the direction of the swells rolling under the canoe. The trade wind swells comes from an easterly direction, north of the rising sun at this time of the year, and heads west, toward the setting sun. By the feel of the canoes pitching and rolling in the swells, the navigators can maintain the heading of the canoes in the daytime, or when the stars are hidden from view at night.

An Online Planetarium

To discover which bright stars are rising and setting at this time of the year and at about what time at night and in what approximate direction, log onto the Interactive Sky Chart at skytonight.com (works in most Java-enabled Web browsers): http://skytonight.com .

In the menu bar on the left, under "Observing" choose the 6th item, "Interactive Sky Chart" and click on the red name in the first paragraph of the page that comes up.

Use the LOCATION /CHANGE button to set the latitude and longitude of the canoes (you can set the position in degrees and minutes, but to the nearest degree is probably good enough: e.g. 17.5 degrees N latitude can be rounded to 17 or 18 degrees.)

Use the DATE & TIME / CHANGE button to set the date; the time can be changed with the arrow buttons to the right of the date and time. You can use this button to view the sky at various times of the night.

The SELECTED VIEW box at the top left will allow you to move the view 360 degrees around the horizon, N, S, E, or W. The MAXIMIZE button creates a full screen of the horizon view. You can scroll around the horizon on this full screen as well.

January 28, 2007 | PVS