Paper Charts and GPS

[Ex-Calif]

Certainly a lively discussion - Here is another place where electronic aids can help.

Very near us is a navy base. To get from Changi to the Volvo races we had to pass around the restricted area. The restricted area is an area marked by a rectangle of yellow bouys. They are all identical.

We ran around on the chart plotter and another boat ran around on charts. They eyballed the middle far side marker with a pair of binoculars, referenced it to the chart and set a course.

We entered the corner buoys as waypoints and folowed the magenta line.

We re were certain we had the correct waypoints and the other boat was entering the restircted area. We moved the cursor on our plotter to the starboard of our track and the label changed from "Eastern General Anchorage" to "Restricted Area" in red letters.

Just about that time the automated boat detector at the Navy base sounded and this huge freaking horn started going off. 2 minutes later the MPA boat came out and boarded the other yacht for being in the restricted area. The skipper now has an appointment with MPA and will probably get fined and could lose his license.

Having said all that - I use coastal charts all the time.

You use the tool you need at the time you need it. Nothing is mutually exclusive.

[Pblais]

Just about that time the automated boat detector at the Navy base sounded and this huge freaking horn started going off. 2 minutes later the MPA boat came out and boarded the other yacht for being in the restricted area. The skipper now has an appointment with MPA and will probably get fined and could lose his license.

Well here on the Chesapeake if you get into the Patuxent Naval Air Station range. They do all that and then the just start shooting. Even though they are not aiming at and you might be outside by a mile the concussion will move the sails.

You need to know not only the coordinates of where you are but need to know "where you are".

[MarkJ]

Originally Posted by Pblais

Patuxent Naval Air Station range. They do all that and then the just start shooting. .

Thats doesn't happen here in Australia. Anyone can sail into restricted waters. The Navy can't afford the ammunition

[catty]

Originally Posted by MarkJ

I reckon, seriously, that within 5 years paper charts will be gone.

Those that don't use them or haven't used them should take a sail into a new port with one. Or try crossing a barred river entrance from the sea.

Instantaneous positioning, exactly accurate, and right in front of the helmsman’s face.

Our course over the recent bar into this estuary was within meters of breaking waves. Only the instant updating of out path along our route enabled us to manoeuvre the few meters left and right to maintain our course exactly enough to enter safely.

The whole way in we NEVER once sighted the physical leading markers. The difficulty being, of course, that by the time one without a chartplotter had realised that they would have been committed to the entry or face turning their boat into open breaking waves.

A bar is just one point of nav where paper and a hand baring compass are useless. Entering any port for the first time there is too much nav information so it becomes a sensory overload. No one can be expected to remember all that s required of a unfamiliar commercial or busy port.

And running up and down to the nav station plotting lat & Lons takes too long. Bringing a flimsy paper chart into the rain not practical.

And 'eyeballing'? Thats probably one of the most inaccurate methods of navigating! How many times an hour do you look at something and not 'recognise' it before it slowly becomes apparent, or visa versa? Things look different from the deck of a boat with your hand on the wheel!

Mark

What a load of crap. So you are prepared to believe what you see on your trackplotter and not pull your head out of your backside and actually look.
Firstly , bars can change within weeks/months depending on the river flow ( rain fall). Leads are often set on tracks or physically moved by harbour masters/fishermen/volunteers to the correct alignment as the position of the banks change during the season. Often on the less heavily used bars no charting authority is notified of the changes.

When crossing bars , irrespective of how much money you have spent on electronic charting, its probably a good idea to have a bit of a look first. Check which way the current is running, swell height, tide height and unless in some dire emergency, cross in daylight in good visability.

[btrayfors]

Amen.

One has only to look at postings in two recent threads to see that the views put forth here re: electronic-only are not only dead wrong but very dangerous:

http://www.cruisersforum.com/forums/...ver-22664.html

SSCA Discussion Board :: View topic - Very disappointed with C MAP charts of Mexico

Experienced navigators know this is pure garbage. Hopefully, others will not be led astray.

Bill

[Ex-Calif]

Originally Posted by catty

When crossing bars , irrespective of how much money you have spent on electronic charting, its probably a good idea to have a bit of a look first. Check which way the current is running, swell height, tide height and unless in some dire emergency, cross in daylight in good visability.

Originally Posted by btrayfors

Amen.

One has only to look at postings in two recent threads to see that the views put forth here re: electronic-only are not only dead wrong but very dangerous:

If this discussion is about paper vs. electronic charts then I propose that the paper charts would also be useless in this example.

What is funny is that GPS charts are usually a re-creation of paper charts. Any innacuracy in the paper chart transfers with the chart.

[Captain Bill]

btrayfors, sorry to disagree with you but the issues with Alligator river and C-map have nothing to do with Electronic charts. These issues also exist on paper charts. First of all C-map and other proprietary charts which are only updated once or twice a year and are used in chart plotters are really very limited and people need to understand that, just like one would need to be wary of year old paper charts. I had a friend using "real" electronic charts downloaded from NOAA on a trip from NC to the Chesapeake last spring. He was gone a month and while he was gone the markers at the mouth of the Alligator were moved while he was up north. He did not have access to the internet while he was enroute and missed a weekly chart update. While following his old chart he managed to bounce his keel on the bottom when returning home. His chart was less than a month old. The newest paper chart he had available was nearly 90 days old. If he had access to a print on demand outlet I guess he could have had an up to date paper chart, but if he had that he could have had an up to date electronic chart. Then again if he had listened to the morning notice to mariners broadcast he probably would have noted the recent marker changes. By the way my friend did not attempt to blame the charts.

I personally dislike the C-map charts used in my chart plotter. For Electronic charts I keep a computer on board hooked to its own GPS loaded with real NOAA charts which I update regularly. Electronic charts are no more dangerous than paper charts. Until someone starts building a chartplotter that can download real, up to date, ENC or raster charts one must realize that chartplotters are very limited and should not be trusted any more than out of date paper charts. It's not a problem with the technology, it's a lack of understanding of the limits of that technology and the fact that we are not living on a static planet.

[btrayfors]

Captain Bill,

You're welcome to disagree with me anytime :-)

Mostly, I agree with what you said about updating. But I don't agree that this "has nothing to do with electronic charts".

Yes it does....not the charts themselves so much as the mentality which often accompanies the use of electronic charts and chartplotters by some (read "many") sailors who have no real grounding in either charting, piloting, or navigation of any sort. Rather, they are all too willing to believe that their boat is where it is shown on the little screen, and to "follow the magenta line" or some such nonsense. That, if you'll read further in the thread, was the sense of many very experienced sailors and navigators who responded to the Alligator River grounding thread.

One other point: yes, electronic charts of all sorts are (mostly) recreations of paper charts. But the point seems lost on many that all electronic charts are not created equal.

Paper to raster is exact....a photo reproduction, if you will. If there are errors on the paper chart, they'll be the same on the raster chart. Raster charts look exactly like paper charts because, for all intents and purposes, they are the same.

Paper to vector charts is a whole different thing. It involves a great degree of human intervention to "digitize" the paper charts. This is like tracing a map thru tracing paper, only with an electric wand. In so doing, the accuracy and completeness of the reproduction depends very much on how carefully the digitization was done and, very important, how carefully were the checks and controls exercised to be sure that the vector chart is an accurate representation of the key elements of the paper chart. NOAA expends a lot of effort in this control function, as do some other government charting offices. However, the non-government vector charts produced privately may or may not have the same level of accuracy....many have found that they often do not, and contain both errors of omission and comission. And, they don't look like paper charts at all, which for some persons can be confusing.

Clearly, I prefer government-sponsored raster charts, and that's what I use aboard in addition to the real paper charts which look exactly the same. However, raster charts cannot be run on dedicated chartplotters -- yet -- so must be run on a computer with appropriate navigation software. This has at least two downsides: (1) the computer is much more likely to crash than is a dedicated plotter; and (2) the computer-based chart display uses a lot more power than do dedicated chartplotters.

But, the upside is that the navigation software available to display these charts is very powerful, extremely useful for planning as well as monitoring progress, and can handle both vector and raster charts as desired.

Understand that I am not against electronic charts at all. I love them and have used them extensively in many thousands of miles of both offshore and coastal passages. But, I think a well-prepared cruising boat needs to carry both paper and electronic charts -- against that day when the electronics break down, of course, but also because it's often much easier to refer to a paper chart than to an electronic chart for planning purposes or for just perusing possible stops, anchorages, sights ashore, etc.

Bill

[Charlie]

what a lively discusion this has become. What I was trying to figure out is this: When you have a GPS position and you transfer it to a paper chart I realize that you are not necessarily accurately positioning yourself in your real world location. There could be different causes for this including but not limited to : 1) The GPS and the paper chart using different datum and 2) the paper charts might have a different accuracy level then the GPS. What I am trying to figure out is when you are in postion with E charts and it doesn't look right are the paper charts going to be be accurate enoguh that you can do your costal navigation and figure out where you are.

Now to way in on the turn that this thread has gone. I use both paper and Echarts. I also use the depth sounder and I confirm where I am on E charts by doing rough range bearing calcs. I also use the radar. I don't see any reason not to use any tool that is available. sometimes you get too much data and need to decide which data is best. If there is a problem I stop the boat and discuss it with the admiral. We don't proceed until we are in agreement.

On a recent trip down the California Coast we were getting set to pull into Morro Bay. It has a tricky entrance and has lots of current. We came in under clear weather. I was using the radar to get more comfortable with it. I had a visual on the approach bouy. It was only 1/4 mile away. Just then a fog rolled in. I had studied up on the paper charts and noticed a comment that the buoys were arranged for the best entrance to the harbor and might not be where they were plotted on the charts. Though I could see the approach buoy on the radar I couldn't see the numbered buoys b/c they were hidden from the radar by the breakwater. I could have followed the buoys in according tot he E chart but decided against it. I waited for the fog to clear. It didn't. We decided to head for Port San Louis. By looking at the charts I realized that I could get into there at night even in the fog. I don't know what woudl have happened if I had just followed the E chart into Morro Bay. In thinking about it I would have trusted the radar location of the buoys over the E charts. BTW this would be considered a bar type entrance as well. They move these buoys depending on where the best entrance over the bar is. A prudent navigator uses the tools that he has avaialble to him. E charts, paper charts, or radar each have there place and one is not better than the other.

[btrayfors]

Good questions and examples, Charlie!

You're right, of course: there's no reason not to use every aid available and, I would add, there's every reason to use them :-)

In most instances, there's little reason to believe the e-chart (raster or vector) is likely to be better than the paper chart, with the important exception of nav aid locations and obstructions which may have moved since the paper/raster charts were prepared and -- if the vector chart has been updated faithfully -- the new locations might be better depicted on the vector chart, simply because the new information is included.

However, the positions of major things -- coastline, deep channels, bridges, etc. -- are unlikely to have shifted.

Since you have radar, I'd depend on that to provide much more accurate positioning data than do paper charts and/or electronic charts. Providing, of course, that you know how to use it :-)

Both GPS and radar are wonderful tools. Once in winter before I had radar I used two identical GPS units aboard and computer-based electronic (raster) charts, with preprogrammed waypoints, to navigate in absolute pea soup fog the last 30 miles up the Potomac, including finding the opening section of the Wilson Bridge when I couldn't even see the bridge! We did it slowly and carefully, only saw one lighted nav aid the whole trip and, of course, used our fathometer and our ears as well as our eyes and senses. Safe trip, no problems, great sense of accomplishment, but it would have been a heck of a lot easier with radar :-)

Bill

[Ex-Calif]

Sometimes our discussions include a lot of example and embellishment in order to make a point. It is hard to summarize what is going on.

- Charts - Primarily vector and raster. Both can contain errors. Vector charts require significant human intervention to produce. GPS with vector charts may avail of more frequent updating.

- GPS - will accurately plot the lat/lon of your vessel. When using echarts the datum must match. When transferring lat/lon manually to paper charts the datum must match. Caveat emptor on chart errors in each case.

- Passage making - In almost all cases eCharts are fine as are paper charts. However positional errors have been found for hazards like reefs and groundings have happened. This is a function of the charting not the GPS innacuracy. (Unless someone has a real example where the GPS lat/lon was innacurate)

- Making landfall - Harbor and channel entrance buoys can move between chart updates. Bars can move between chart updates. When making landfall in new harobors it is prudent to make landfall during daylight clear conditions and use MKII eyeball navigation including hand bearing compass, landmark identification and depth sounding as required.


The tempest continues to fallback to the charts and the accuracy or innacuracy of them. This issue remains when using paper or GPS chart plotter.

- Hazards - I just want to point out that when setting a course either with paper or echarts reefs and other hazards can be identified. The position on the chart can be in error. So how to avoid?

You could aim off quite a ways but how far? And if you aim off have you aimed towards the error or away? Using celestial navigation you are likely to be a few miles off just due to the nature of that navigation method. With GPS you can accurately set a way point and be confident that you are positionally correct. However the hazard may actually be under your way point if the chart is in error.

Here's the key. You know the hazard is there, somewhere. When approaching, just make sure you have the MKII system up and running until the hazard is identified or you are more than reasonably sure it is cleared.

[RBEmerson]

We are all a battery failure away from the Age of Sail. 'Nuff said.

[MarkJ]

Originally Posted by RBEmerson

We are all a battery failure away from the Age of Sail. 'Nuff said.

I haven't had a battery failure in car or boat battery for more than 30 years and that one was a 1966 car in 1977 in my last year of school.

As for AA Alkaline batteries I have never had a failure. Sure they run donw from use, but I have never had a failure.
Further one carries more than one battery. This boat has 3 - 2 house and 1 engine and the draw is stocked full of AA, AAA, AAAAAAAAAA and anything else a battery maker can print on a slim cylindrical object

Go back to the Slocums goat analogy.... If sailing with a goat make sure chart plotter isn't wrapped in hay i.e. carry a spares.. both batteries and plotters.

[skipmac]

Originally Posted by Captain Bill

It's not a problem with the technology, it's a lack of understanding of the limits of that technology and the fact that we are not living on a static planet.

Well said and right on the money!

[Exocet]

Paper charts VS Electronic, Hmmm. What came first,.. the chicken or the egg??...who's tha chicken, who's tha egg??..Paper charts were first, and now electronic charts are just the CAD file in which the paper charts are printed. Niether should be trusted farther than you can throw them, Literally!! There are many problems with paper charts as well as GPS solutions, however the main issue is usually not the same datum, the World Geodetic System of 1984 (WGS84),North American Datum of 1927 (NAD27), North American Datum of 1983 (NAD83), and a few more. Another error in a GPS solution comes from solar activity and the earths magnetic fied.
Now out in the big blue sea I have no problem using the GPS, for any coastal navigation though, I put my chart beside me in the cockpit and am aware of were I am at all times! If the GPS says I am some where else, who craes, it may not jive with the chart datum, if all of a sudden I cannot place myself on the chart, or there are incorrect depths, now I care and it's time to slow down, dead recon until things make sense again.
Just a quick note, I work as a surveyor using GPS daily achieveing accuracys of 10mm. Most errors in a GPS solution mainly affect sub-meter accuracys, so for the hand held or navigational GPS with a solution of only +/- 10 meters, the are 99.9% reliable, were they say you are on land, when indeed you are at sea, problem is the datum does not match.