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Go Back   SailNet Community > Skills and Seamanship > Seamanship & Navigation
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Seamanship & Navigation Forum devoted to seamanship and navigation topics, including paper and electronic charting tools.


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  #1  
Old 05-07-2010
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Why I do not trust chartplotters.

I have an emotional attachment to my PC based raster charts because they look like charts. I now have some additional confirmation why I did not trust chartplotters and vectors charts.

1) South of Victoria, BC is military activity area WK. On some chartplotters it shows as a wreck.

2) Atkins Reef in Trincomali Channel is marked by a Port Hand Bifurcation Day Beacon. Last week I saw a chartplotter with vector charts show it as Starboard Lateral Daybeacon.

Any similar experiences?

Jack
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Old 05-08-2010
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Yeah, unfortunately this is a by-product of the difference between Canadian and American government intellectual property. In the States intellectual property like this is property of the people, in Canada it's "Property of Her Majesty the Queen". Long story short the distribution of Canadian electronic chart data is a mess.

I've seen rocks out of place, ledges missing, day beacons incorrectly labelled. Cadboro Bay misspelled, and the buoys in and around Victoria Harbour missing (Thank God for paper). Some of this is forgiveable in a $150 hardware store special, but less so in a freshly updated $800 nav package.
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Old 05-08-2010
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Plus most of those electronic chart companies don't correct or up grade the charts in a timely manner. And you are required to suscribe to their chart upgrade service in order to keep your ECDIS reasonably up to date.
You notice that I didn't say completely up to date!
Chart corrections come out weekly in the Notice to Mariners...
Your suscription for ECDIS correction may be twice a year... So you could have major discrepancies in the area that you really need.
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Old 05-08-2010
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My PC based chart program displays either type of chart, so if I have any question about what my eyes are seeing and what my program is showing, I can double check within the program (or bring up SeaClear) or check my paper charts. So far, from Clear Lake, TX to Annapolis,MD (via the Keys, the Gulf and the GIWW) I haven't experienced that kind of problem. Trust, but verify.

So far, my only problem has been an area of the Potomac River that went blank due to a program glitch, which I was able to advise Fugawi of at the Annapolis Boat Show.
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Old 05-08-2010
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Chart Plotters like the kind that Garmin and others make use vector not raster charts, but updating those types of plotters may take as long as a year. I know because I have both a stand alone plotter at the helm, and a hand held GPS.

This is a totally different story on my PC navigation program Coastal Explorer, where I can download the lasted NOAA vector and raster chart updates anytime they are available. The updates are made often for vectors, and it only takes moments to get them. Raster charts are only updated when a new map is made with the corrections, and that can take years before many areas are updated.

I know a man that just finished sailing from Mexico to Nuku Hiva, Marquesas, and he said about his PC navigation program "My Nobletec charting is right-on."
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Old 05-08-2010
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It's not just electronic charts. I've seen errors on non-government paper charts too. Maptech comes to mind.... They probably have errors the same way the e-charts do, errors or omissions in transcribing and labeling of nav markers.

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Old 05-09-2010
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I'd point out that chartplotters are a nicety and a luxury, but not a necessity. The MK I Eyeball still should be your primary navigation tool. In most areas, at least near shore, the MK I Eyeball, using coastal pilotage techniques, is quite good at keeping a pretty accurate location
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Old 05-09-2010
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Lessons

Geez. Or we could just have the Coast Guard stop changing all the buoys all the time. I know they added one near a rock at a port close to here. The local yard is already complaining that it's bad for their repair business, since people don't hit the rock any more. Seatow could get more business in places with shifting sandbars if the Coasties didn't keep moving those pesky red and black things. We could also navigate with just a leadline, and no charts at all. Perpahps it's best to simply be aware of the limitations of whatever system we use - even if it's supposed to be super-sophisticated. The USS San Francisco learned this the hard way a little while ago. Putting everything together and keeping the boat & crew safe is the Captain's job. Nobody said it was easy. That's why there are lots of crew and one captain. You're right to complain: you're aware of the problem, and you're doing the right thing by making sure others are aware of it as well!
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Old 05-20-2010
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Quote:
Originally Posted by jackdale View Post
I have an emotional attachment to my PC based raster charts because they look like charts. I now have some additional confirmation why I did not trust chartplotters and vectors charts.

1) South of Victoria, BC is military activity area WK. On some chartplotters it shows as a wreck.

2) Atkins Reef in Trincomali Channel is marked by a Port Hand Bifurcation Day Beacon. Last week I saw a chartplotter with vector charts show it as Starboard Lateral Daybeacon.

Any similar experiences?

Jack
What tool of navigation is 100% accurate? Paper charts, raster charts? vector charts? celestrial navigation? Answer: none.

You need to assume that there can be errors with any of then, look at all the information you have available, compas, chartpoltter, paper charts, depth sounder, radar, your eyes and etc. If the info you are getting from each is consistent you are probably OK. If not you need to find out why not.

99.9999% of the time my chartplotters, fixed and hand held provide accurate information. You just can't assume that it will always be the case as you have noticed.
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Old 05-24-2010
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Globally the whole business of updating charts is in a bit of a mess at the moment and probably will be for a while. Most national hydrographic offices are fairly well set up for maintaining their paper portfolios. Raster charts are commonly produced as facsimiles of the paper charts so these can usually be maintained in a fairly timely fashion. Vector data is often generated from the raster data set so the updates for these will follow along sometime later. End of the chain are the third party chart producers who copy the official data sets so naturally their charts are last in the update chain – this group includes the producers of several of the chart formats commonly used in plotters.
If you are running an ECDIS and subscribe to one of the official update services then, it’ll cost ya, but you will receive weekly updates to your chart holdings (vector or raster). So this means that your charts will all be quite well up to date and consistent – in areas commonly used by commercial shipping anyhow. If you are using the NOAA raster or vector data then you can manually download updates and stay reasonably accurate like that.
But this is all changing because this is not a good way to handle vector data and vector data is the future. Separate issue as to why it is the future or whether it is the right future but for now it definitely is the future. You see, really, vector data wants to be in a database of ‘objects’ where an object is something like a light or a depth contour or a traffic lane. This object database is updated from raw survey data and reports. Charts can now be created straight from the database. Vector charts are easy. Raster charts are a bit more problematic because in this new world the time served cartographer has been left out of the process. Ever noticed that vector charts do not look as good as raster? This is why, the dumb computer (and they are all dumb) is trying to do in a fraction of a second the same layout job that a skilled cartographer might have taken several days over. It just don’t work so well.
So with vector leading the way then raster charts will become secondary and paper charts end up bottom of the pile. They may not look as good as current paper charts and will almost be the last items in the chain, rather than the first, to be updated. Last in the chain will always be the third party chart producers however as their update feeds become predominantly more electronic (just another output from the database) then these updates should become more timely.
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