Keeping Safe From Chart Inaccuracies
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More Articles From Online Book: Navigation and Marine Electronics:
- Knowing Where It’s At
- Electronic Chart Dangers
- Keeping Safe From Chart Inaccuracies
- A Useful, But Potentially Deadly, Feature of Navigation Apps and Plotters
- Chart Plotters And Autopilots, Never The Twain Should Meet
- Do You Still Need Paper Charts?
- Backup Systems
- 11 Tips for Safe Navigation With Phones and Tablets
- 12 Electronic Navigation Tips From a Cruise on Someone Else’s Boat
- Marine Electronics System Recommendations
- 6 Tips To Stop Marine Electronics From Ruining Your Cruise
- Marine Electronics Recommendations—Communications
- Marine Electronics Recommendations—Radar
- Which is Best For Navigation: Plotter, Computer or Tablet?
- Coastal Passages, Part 1—Making a Plan, 10 Tips
- Coastal Passages, Part 2—Rounding Headlands
- Coastal Passages, Part 3—Off We Go
- Costal Passages, Part 4—Keep On Plugging
- Coastal Passages, Part 5—On To The Finish
- Passage Anchorages
- Navigating in Fog, Part 1, The Tools
- Navigation in Fog, Part 2—Preparation
- Navigation in Fog, Part 3—Underway
- 8 Radar Use Tips
Vector-charts don’t give us easy to understand feedback about limits of accuracy.
And sometimes feeling uncertain about where we are makes us safer, because we pay more attention.
That was, despite the translation, a good read. Thank you.
Excellent article, another not quite as detailed, but also very good in similar vein by English writer Tom Cunniliffe
http://www.yachtingmonthly.com/sailing-skills/how-to-use-vector-charts-safely-33747
I certainly agree with his recommendation of running a raster chart in the background is vector is the primary system.
Personally, even with all the electronic information available I still like to have a paper chart beside me. I have the same (dinosaur?) preference when reviewing engineering drawings – CAD screens do not always portray the big picture.
I think the most basic rule for navigators and weather forecasters is to remember to ” look out the window” at regular intervals and not get mesmerized by glowing screens.
Hi Jo,
I really like the last line of your comment. No question, over confidence is the biggest danger in navigation.
John, it’s not just cruisers and cruise lines, I personally know two military officers whose careers were truncated by chart accuracy — in one case the ship had to be broken up where she ran aground. I believe the charts in use were ENCs.
Hi Chris,
Yikes, that’s an alarming statistic.
am always happier with the current weather charts than a forecast (more like ‘nowcast’ usually), and those provided by bermuda wther svc via the net (weather.bm) are always beyond excellent and with nice range and detail…i have experienced more than a few mistakes verbalized from the noaa wthr radio broadcasts such as reversing tidal states as in refering to high when shhould have been low…major error never to be anticipated except by only the most paranoid…cheers, r in tampa bay for another month or so before heading to the antilles for a while
Your point regarding the position accuracy of floating aid to navigation (Bonus Tip #2) is well taken. In the 1970’s, I ran a search in Florida, between Rebecca Shoals and the Dry Tortugas, for a crashed Air Force fighter. Our search area was charted based on eye witness information from shrimpers who were anchored adjacent to a navigational buoy. After six unsuccessful days of searching, we discovered, quite by accident, that the Coast Guard had set the buoy 8 miles! from its charted position. Using the actual buoy position, we found the plane wreckage in a few hours.
John
I also use Nobeltec Trident and predominantly coastal cruise the Australia East Coast. Trident along with many other navigation programs allow for satellite overlay on the charts.
Do you have a comment as to the accuracy of using this to confirm chart accuracy.
I enjoy reading yours and other contributors articles.
PHIL
SV Kirralaa
Hi Phil,
That’s an interesting idea. I have never tried it, but I would guess that the resolution would not be enough to make the behaviour I detail in the post above safe.
Having said that, I would think that overlying the satellite to check the datum accuracy of a remote and poorly charted coast like Greenland might be useful. I will have to try it.
Quick story, I was in the Greek islands and was heading to a very small harbour. I was chatting to another sailor and he said be careful of the reef immediately outside the entrance of the harbour. I checked the chart (paper) nothing, chartplotter nothing, harbour pilot, nothing. Tried google maps in satellite mode and bingo there is was, a patch of very light water. Now the dilemma, how was I going to avoid it if I didnt know where it was? So I took a view that if the satellite view was accurate on my tab to my GPS position before I set off, it would probably be ok 5 miles away. Anyway with stomach slightly in my mouth, I navigated in on google maps satellite – worked a treat! Still not convinced it is bomb-proof but ……..
Hi Charles,
We have done the same when off the charts in places like Baffin and Greenland and that before the data was as good and before it integrated into charting software. In short, it’s a great tip.
A related tip in coastal areas is to use the “History” control to show all the available satellite images for the area under review. Aspects of tide and water clarity can reveal a great deal in certain images that are otherwise obscured in the default most recent view. I do not rely on Google Earth, but it is one of the more helpful nav aids in our route-planning process.