MAX EBB — I
t was good to see that someone had finally read my instructions about how to prepare their boat for an inspection. The storm jib hoisted, the trysail bent on, jacklines rigged, and emergency steering system set up and ready to demonstrate. Even the anchor rodes were run out along the dock, ready to measure. This inspection would go quickly, and I might even have time to go sailing later in the afternoon. By the time I went below to find the skipper, I had checked off most of the deck items: Toerail around the foredeck, lifeline stanchions secured in place, padeyes for harness tethers. Things were just as well organized downstairs, with
all the required PFDs, harnesses, tethers, flares, and other emergency items on display. Still no sign of the owner or skipper, but there was a file folder on the chart table marked "For Inspector" that contained copies of the raft certification and other required documents. The inspection checklist was almost complete before the owner — or in this case, the owner's rep — came aboard. "Max!" cried Lee Helm as she jumped down the companionway ladder. "I didn't expect you to be our inspector!" "Well," I countered, "I didn't expect you to be on the crew. Did they leave you in charge of inspection prep? And are you on this boat for the Hawaii race?" "For sure," she said. "Nice ride, huh?" "It looks fast," I agreed.
I
checked off some more basic items in the cabin — bilge pump handles, floor boards secured, ditch bag within easy reach — when I noticed a track chart taped to the bulkhead next to the stowPage 102 •
Latitude 38
• June, 2014
age plan. "Looks like they might have gone a little too far north in the last race," I said. "Is that to remind the crew not to take that route again?" "That's just the 'passenger chart,' like what they post on a cruise ship," said Lee. "And, like, it's not as far north as it looks on that projection." "Right," I said. "I understand that the track chart is on a Mercator projection, so the great circle course is a curve to the north of a straight line. I guess when you have a spherical earth and make it into a flat map, it's impossible to show
"For most applications the Mercator projection is more practical because it's, like, conformal and loxodromic." Against my better judgment, I asked what those words meant. "Conformal," Lee explained, "just means that shapes and angles are preserved, as long as their extents are small compared to the size of the earth. That is, a circle will always look like a circle, and a right angle will always be a right angle. Now, the scale may change a lot. We have the 'Greenland syndrome,' whereby Greenland looks bigger than South America, even though it's really much smaller. But the shape of any reasonably small feature is preserved accurately. Like, a bay in Alaska will appear five times the size of a bay in Brazil, but it will still have the right proportions." "That's because the meridians all converge at the poles, but the Mercator projection keeps them at the same distance on the chart," I volunteered. "So the scale becomes infinitely large at the pole." "And the chart would become infinitely large at the pole too," added Lee.
The track chart at the top shows division winners of the 2012 Pacific Cup, in Mercator and tangential projections. When you see the great circle as a straight line, it doesn't look as if the winners went all that far north.
"That's why a Mercator projection — at least one aligned with the equator — never reaches the pole. But shapes and angles are preserved intact, so the projection is conformal." "What was that other property?" "Loxodromic," Lee continued. "That just means that a straight line from point A to point B will have the same heading over its entire length." "In other words, a rhumbline course," I said. "But, like, in this case 'rhumbline' is not the shortest distance from A to B.
the shortest distance as a straight line." "That's not true at all," Lee informed me. "There are lots of ways to represent a sphere on a plane, and some of them show all great circle paths as straight lines." "Well then why don't we use them for navigation?" I asked. "Seems like it would be much more intuitive."
