Feb. 4, 2000--Lessons in Navigation

Source: Sam Low

For the last week, Hokule`a's student navigators--Shantell Ching (the principal navigator) and Ka`iulani Murphy and Kahualaulani Mick (apprentice navigators)--have been meeting with Nainoa at his house in Tautira village. The meetings are designed to be collegial but the distance between the teacher and the students, even though they are the best of friends, is often apparent.

Much of the teaching comes in general principles presented by Nainoa through questions--like this one: "Suppose you think that you are 9 degrees South by your dead reckoning and you measure Kochab cross the meridian 6 degrees above the horizon--where are you?"

The students knew that a meridian altitude of 6 degrees translates to a latitude of 10 degrees South and they understand that Nainoa is asking them which method of determining their position should take precedence--dead reckoning or star sights? Are they at 9 degrees South as determined by their dead reckoning or 10 degrees South as determined by the altitude of Kochab?

There is a long silence--eventually Nainoa breaks it.

"When you get a good star measurement I'd trust it. Start your dead reckoning from the point indicated by the stars--in this case 10 degrees South."

"Here's another question," Nainoa says "Can you use Kochab as a latitude star even if it does not cross the meridian?"

Normally, the altitude of a star is taken when it does cross the meridian which means when it reaches the highest point in its arc across the sky. Unfortunately, during the first few weeks of our voyage, Kochab will cross the meridian after the sun has risen so it cannot be observed. On February 5th, for example, Kochab's meridian crossing is at 6 a.m. or 0600 as sailors like to say it.

Using a computer program that replicates the motion of the stars across the night sky as well as during long sessions with Will Kyselka in Bishop Museum's Planetarium--Nainoa watched Kochab cross the meridian time and time again. In this way he repeated the process used by ancient navigators--years of patient observation--but he was able, with the use of modern technology, to speed it up. He carefully measured the altitude of Kochab at meridian crossing and an hour before it crossed the meridian and found that the difference in altitude was only a quarter of a degree. "And that's not measurable with the naked eye," Nainoa says, "so yeah, you can easily use Kochab at 5 a.m. to get latitude."

Next, Nainoa steps through a series of more simple problems. When, for example, is it best to hold navigational meetings at sea to assess our position? At sunrise and sunset because without clocks these are easily observable times of the day.

What to do if sailing into the wind and inexperienced helmsmen are having trouble steering an accurate course? Trim the sails and move weight around on the canoe so she steers herself.

How to determine the amount of leeway of steering error due the force of the wind on Hokule`a's sails? Watch the angle that the canoe's wake makes with her hulls.

How far away can you see landfall? It depends on the height of the island and, of course, the visibility. (A high island like the Big Island of Hawai'i--13,789 ft. high--can be seen from over100 miles away; an atoll, on which the highest points are the top of coconut trees, can be seen from 8-10 miles away.)

How can vog be helpful in finding the Big Island? If you see it, you are downwind of the island.

What is the overall current effect in the doldrums? None, because the currents are too variable to predict. (Click here for more Navigation Questions on the Web.)

Nainoa's probing questions and his presentation of various scenarios are often accompanied by stories--a sharing of mistakes he has made with the obvious intent of indicating that navigation is, after all, a process of learning in which there is much trial and many errors. Take the case of sighting the Big Island at the end of the 1995 voyage, for example: "We were making our approach at night," Nainoa says, "and I was pretty confident that we were getting close but all I could see ahead were layers of light pink shading to purple then black. We couldn't see the island because of all the vog. Snake saw something glowing ahead. A fishing boat? We couldn't tell. It was a moment of panic. All of a sudden Snake said, "Hey, I think it's the volcano." It will be like that, you go through moments of panic and even hallucination combined with moments of intense insight."

The training sessions between navigator and students usually last for an hour or two after which the navigators either study together or by themselves to memorize the stars or various "formulas" for determining leeway, or current set, or go over their mental maps of the course to Hawai`i.

"Don't forget that this should really be fun," Nainoa told them at the close to one meeting this week. "Don't lose your excitement and your instinctual sense of knowing by too much studying. You have each other--remember that. I look forward to seeing you huddling together trying to figure things out. And don't worry. I won't let you do anything foolish but I also promise you, that I will let you do this trip--as much as possible--on your own."