A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Questions asked about Volvo Ocean Race accident
From: Lu Abel
Date: 2014 Dec 2, 18:32 +0000
From: Lu Abel
Date: 2014 Dec 2, 18:32 +0000
You're right about electronically scanned images of NOAA's paper charts. Originally developed by a third party (can't remember the name, but IIRC "BSB" was their corporate initials). NOAA actually calls them RNC (which I assume stands for "raster nautical chart") format.
Unlike RNCs which are scans of paper charts, ENCs (which conform to the international standard S57) are simply a "bucket of bits" -- data which it's then up to the program to figure out and display. But with a quality program, this can be an advantage. For example, soundings are just a data point: Lat, long, and depth (I believe in meters). Want depths in feet? -- no problem, the program can simply convert on the fly and display them that way. Prefer fathoms? -- again, no problem.
If I zoom out the program can choose to keep and display "significant" depths -- eg, a reef or sandbar -- while skipping others so as to not simply overwhelm the display.
Chartplotters were originally developed because microprocessors were slow and memory expensive. But with my iPhone having more processing power and memory than my deskside computer of 20 years ago, I wonder why Raymarine, Garmin, and the other recreational marine electronics manufacturers continue to manufacture chartplotters instead of developing a unit (certainly within today's technologies) that displays ENCs.
I've downloaded OpenCN but haven't had a chance to try it yet. The two top-end PC-based navigation programs, The Cap'n and Rose Point Navigation's Coastal Explorer, both handle ENCs. I spoke with a Rose Point rep at a recent boat show and he said they were working on porting their program to a Windows tablet. Okay, Windows tablets are certainly the least popular of tablets, but Coastal Explorer on a tablet would likely be a lot cheaper and capable of much more than a chartplotter. And no questionable chart plotter cartridges!
You're right about ENCs being kept up to date. My understanding is that NOAA now keeps all chart data electronically. When a Local Notice to Mariners is published that affects chart data the electronic database is updated (as you note within a week or so) -- and the ENC format charts are updated immediately.
And, of course, NOAA has gotten out of the business of printing paper charts, so if you go to a local provider, he's got a big inkjet printer and is simply printing an RNC for you.
Will be interesting to see how the Volvo incident evolves.
From: Greg Licfi <NoReply_GregLicfi@fer3.com>
Sent: Tuesday, December 2, 2014 9:16 AM
Subject: [NavList] Re: Questions asked about Volvo Ocean Race accident
I agree with you about 3ed party charts - they are junk. Electronic charts are available from NOAA in both BSB and ENC formats. BTW: While not
the "professional ENC format" there is nothing wrong with the BSB format for pleasure boaters - BSB's are made by NOAA they raster scan their
own NOAA paper charts. I use a PC program called "opencpn" it is great! it loads both BSB & ENC charts which you can download directly from NOAA,
and NOAA to its credit is now updating it's BSB and ENC formats on a near weekly basis - I was told this by a NOAA manager; they simply take the
"Notices to Mariners" and update the e-charts as a sort of 'Notices to Mariners' for the 21th century! many chart plotter manufacturers use the data
cartridge as a recurring revenue stream, selling subscription services (as down loads or new cartridges) others can't even be bothered doing that
and just tell you to crosscheck with a current paper chart (duh!) I also teach navigation and safe boating with the CG Auxiliary. A problem that I have
come across more and more is people just plug way points A & B into the chart plotter / autopilot and never take closer look at the chart until they
run over something. Here on Long Island sound both the north shore of L.I. and the south shore of CT. are foul so it happens more than you would
P.S. opencpn also shows tides & currents and plots celestial LOP's
On 12/01/2014 08:11 PM, Lu Abel wrote:
I think the first question to be asked is what sort of "electronic charts" were they using?
Let's remember that commercial vessels are now allowed to use electronic charts and are not required to have paper charts aboard. But these are "professional grade" electronic charts, published by national charting authorities like NOAA.Recreational sailors have two choices -- "chartplotters" that use data produced by independent third parties and computer (typically PC) - based programs, some of which can read the professional "ENC" format charts.It's not clear which sort of "chart display" the boat was using. My limited experience with ENC-format chart displays tells me that they would likely display an important navigational hazard regardless of the zoom level of the display.
I teach navigation at all levels for the US Power Squadrons and I always caution my students about chartplotters because of the third-party data cartridges they rely on.
First of all, I have never heard how the cartridge producers check the accuracy of their data. For example, do they do something as simple as verifying their aids-to-navigation data against the Light List?? I have visions of poorly paid third-world workers who are absolutely ignorant of navigation "digitizing" NOAA paper charts.
Secondly, I have seen cartridges with dangerously incomplete data. Right before I moved from the Boston area to the SF area 20 years ago, I visited the Newport boat show one last time. Several electronics manufacturers were displaying their latest and greatest chartplotters (as I recollect, it was when they were first becoming available with color displays). I fiddled with one, scrolling from Newport to nearby Cuttyhunk Island, a popular anchorage for recreational boaters. Cuttyhunk is easy to approach, but there are significant reefs sticking out into the two most common approach paths. The ends of these reefs are well-buoyed. But neither the reefs nor the buoys showed up in the chartplotter! I immediately found the most senior-looking person in the booth and told him that someone could buy one of his chartplotters, take it to his boat, install it temporarily, sail over to Cuttyhunk for the night -- and rip the bottom out of his boat! The gentlemen simply shrugged and said "we don't make the data cartridges."
From: Jackson McDonald <NoReply_McDonald@fer3.com>
Sent: Monday, December 1, 2014 11:21 AM
Subject: [NavList] Questions asked about Volvo Ocean Race accident
According to this article, the reef does not appear on the screen unless the chart plotter operator zooms in -- something unusual in blue water sailing. It seems clear that the captain and navigator did not "qualify" their route as free of danger zones and obstacles using, for example, paper charts. One can also ask whether the location of the reef was accurately depicted on the chart -- whether electronic or paper. http://www.sailingscuttlebutt.com/2014/11/30/questions-asked-volvo-ocean-race-accident/ JMcDonald