A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Frank Reed
Date: 2015 Mar 14, 16:27 -0700
Stephen Davies, you wrote:
"Actually it is a huge ‘rock' - the shoal ground (with four substantial islets, innumerable above surface rocks and even trees!) the Vestas Wind found extends roughly N/S for c.26 miles and ALL of it is awash, drying or with depths <2m. This shows up on the Navionics chart package even at a scale of 1:1,500,000, which suggests that whatever zoom the navigator/skipper duo were operating at, it was either smaller than that - for navigational planning utterly irresponsible - or the C-Map system is startlingly different to many ENCs at small scales."
Yes, this is a significant atoll (though some prefer not to classify it as such since there is no closed lagoon). It was well-known with the features just as you describe above in the sailing directions for the Indian Ocean in the middle of the 19th century. I even have a German globe from the 1930s that has "C Garajos" (a common alternate spelling) marked on it. This is no minor "dot" in the ocean.
The display of small features at different scales is an exceptionally complicated issue in mapping. There is no simple trick to apply, no universal algorithm. This is an aspect of the mapmaker's "art", and fashions and traditions are part of it. I have long believed that charts and maps of all sorts need to display more clearly those parts of the world's oceans that are non-navigable at any time during the tide cycle. Very few maps, for example, display the great sand banks of the Waddensee region off the Netherlands, northern Germany, and Denmark. This is what once rendered Germany nearly land-locked (which was discussed here recently). But any navigator and voyage-planner today should be well aware that this is just how it is. Most maps and charts do not treat extremely shallow, non-navigable water areas as land. Naturally, in any charting software, if you zoom in far enough, the atoll is plainly visible, but at smaller scales it's not displayed.
I read the whole report over the past few days. It's a peculiar document, really probably intended for internal use by the VOR organization and teams, I think. It purposely does not try to blame the team members or the organization (the report is so kind to the organization that it complains mostly about un-answered emails and other minor administrative matters), yet it does rather explicitly blame the charting software. The report says:
"Vestas Wind ran into Cargados Carajos Shoals not because they were inaccurately depicted on official paper charts, and not because they were missing entirely from the C-Map database, but because they were not shown at several scales when the C-Map data was displayed on Expedition software".
Blame the tools, not the users.
The report also uses some techniques well-known from the world of "PowerPoint" obfuscation: details that counter the principal contention of the report are buried in a bulleted list (this is a standard technique for diminishing their significance). In particular, in a bulleted list, we find this little zinger: "the name Cargados Carajos Shoals is shown providing an alert to shallow water". Exactly! The name with the word "shoals" in it was visible to the navigator and the skipper at the smallest scales (wide view), and they acknowkledged this fact. They knew they were sailing right towards something with this name on it. As soon I started reading this report, my first thought was "why weren't they worried about something called a shoal?" It wasn't labeled "seamount"... it wasn't labeled "bank". The label "shoal" should have been an obvious indication of risk. Furthermore (much less obvious, but still...), the name is clearly Spanish or Portuguese (more likely the latter with modified spelling). Anyone who has studied the Indian Ocean should be aware that the Portuguese named many small islands centuries ago. Naturally they named things that they could see. They named places that were exposed and obvious ...exposed and obvious in the 16th century. Something labeled "shoal" with a Portuguese name should have been like a big red light in the middle of the ocean (speaking of a "red light" there's an interesting discussion of the possible origin of the name on the Wikipedia talk page here). Who sails straight into a "shoal" with an old name at 20 knots?
That same bulleted list notes that "the economic boundaries are shown, although when using the default colour pallet, they are difficult to see against the blue 200m depth area and can also be confused with depth contour lines." To me this is a real stretch. The economic boundaries are obvious, and if the 200m depth contour is a distraction, then why the heck are you displaying it in the first place? All contours deeper than 50 meters, and possibly shallower, should be disabled. They are completely irrelevant to a surface navigator. The economic boundaries are defined by land above sea level. The navigator and skipper should have seen them. Perfectly circular arcs are obvious on charts like these.
The report describes but de-emphasizes the primary cause of this incident, at least the way it sounds to me. The region of the Indian Ocean considered open to the racing teams was radically changed at the last minute. Five days of planning was thrown out the window. The navigator and other team members had no time to prepare, and they were sailing into an ocean where they were obviously unfamiliar with the most basic geography. They had no idea that this was a major atoll, a large non-navigable region. It would be like sailing to Bermuda and expecting a towering volcano. Instead of blaming poor preparation arising from a huge last-minute change in the racing area, the report blames the tools. This is an old scenario. The authors of the report were gracious to a fault to the hand that fed them.
Conanicut Island USA
PS: Am I correct in thinking you're the Stephen Davies who was former director of the maritime museum in Hong Kong? And wrote a fascinating report on the value of maritime museums?