So Frank, I had access to “billions and billions” of US Navy charts. For a year before I resigned my commission, the Quartermasters on my sub would give me all the obsolete charts they replaced with updated versions. Even as a West Coast sub, we had charts from around the world… all Mercator projections I believe (although it was 35 years ago).
And what charts I couldn’t scrounge from the Quartermasters, I’d buy from cruisers who were returning to shore.
And then lastly, if all else failed, I’d buy black/white photocopies from Bluewater Books and Charts in Ft Lauderdale - dangerous business those black & whites.
I’d use small scale Mercator projections to cover long voyages like Cabo San Lucas to Nuke Hiva, or Sri Lanka to Aden Yemen, or Gibraltar to Martinique. And then, if I could, medium/large scale charts to island hop. In the end I’d use whatever I could get my hands on… funds were limited.
One night I came breathtakingly close to putting the boat on the reef on Rangiroa in the Tuamotus. I had a wonderful French government chart of the island itself with all its passes and motus and bommies, but first I had to get there from Nuka Hiva using another French Mercator.
Without wind, we were motoring towards the atoll in the whee hours. The diesel was pounding away and I was nestled in the cockpit, facing after, with my foot coaxing the tiller as needed.
The sounder blinked “199” and, as navigator, I was comfortable with our track. We would arrive mid-morning.
Mistake.
It was only after we were right on top of the atoll that I could hear over the racket of the diesel the swells crashing against the reef.
I stood up in the cockpit to investigate the strange sound and nearly crapped my pants. The line of white spume was just ahead… I mean JUST ahead. Thank my lucky stars the moon was bright and the reef line was clearly defined.
I pinwheeled the boat, went full throttle, yelled to my sleeping crew below, and ran down a reciprocal coarse until the line of white was a thin whisper. And for the rest of the night we paralleled the reef line until finally, in broad daylight, we found the reef entrance and entered the lagoon.
There was nothing wrong with my Mercator projection chart of course, just a complete lack of awareness of the currents in the Tuamotus. Wow.
Jack London was right to dub them “the Dangerous Archipelago”.
And then there was the time my DR on the chart said we should have run aground on the island of Nuuk Hiva and it was nowhere in sight, even from the first spreaders.
Good times…
Re: Mercator projection in the news
From: Frank Reed
Date: 2025 Aug 28, 07:24 -0700
Richard Toohey, you wrote:
"...Mercator projections. Never used them for great circle planning but they sure were helpful navigating between atolls in the Tuamotus!"
That sounds fascinating! I, for one, would love to hear more about this. How did a Mercator chart enter the picture? And what did you use it for in the Tuamotus? Also, when was this? Did you have specific printed regional charts as well as atoll charts? Or would that have been luxury?
One of my favorite features of "Bing Maps" is its portrayal of atolls like the Tuamotus and the Marshall Islands. It's easy to see, as in the map image below, that you will bump into something! Many other more traditional mapping products, including traditional globes, modern globe apps, and Google Maps, fail to highlight the vast regions blocked by the reefs and those razor-thin islets that define the boundaries of the atolls and their lagoons.
Frank Reed
File: 
