Adding Up The Navigational Numbers

[CaptainK]

Myself.

I'd used paper charts, along with GPS. That was my idea from the start.

I'd would probably get a plotter for those areas where I would believe, it would be highly recommended.

Cause like someone earlier said, paper charts do go out of date. When a shipwreck or geographical change is made underwater. Thus this makes paper charts obsolete!!

[Alan Wheeler]

The Biggest danger is NOT JUST the fact it is an electronic chart. It is the fact that a little flashing representation of your vessel is placed on top of it. The danger then, it thinking that 1: the chart placement is accurate enough and 2: the vessel placement on the chart is accurate enough, to then rely on navigating with it. There are many many cases of accidents where vessels have run aground becasue they have relied on the accuracy of the system, only to find the accuracy is fallible.
The other aspect is, I don't know how NOAA charts or the electronic primary source is derived. Here in NZ, we have a Navy Hydrographic vessel that plies NZ territorial waters and maps every square inch of it. The accuracey is umparrelled. I imagine that is why we have an inaccuraceyhere in NZ with Electronic charts. Because all the electronic mediums are produced in the US, AND if they come from NOAA sources, then they simply don't have the accuracy. Maybe US charts do.

OK, one final aspect that is most important. If you run aground while navigating by an electronic chart system, you are NOT covered by insurance and the electronic manufacturer will hide behind the "warning" they have printed. So maybe the chart you have is very accurate for your area, but becareful, if something ever goes wrong, it will be a sure smoke screen that all insurance parties will hide very effectively behind and you will find yourself standing out on your own.

[ssullivan]

Richhh once whispered in the wind:
Interesting that you depend primarily on vector charts.

THE problem with vector charts is the 'resolution' errors inherent in them. Vector charts for the most part are derived from sextant/pelorus and lead line data. Using vector charts at resolution/magnification much higher than the original chart is extremely ... WRONG and dangerous. This is due to the mathematical 'stack up' of the original measurement 'tolerance errors' of charts drawn from 'ancient' methods.

Until vector charts are derived from NEW/electronic/laser/satelite, etc. survey data, use them with *extreme* caution, especially at high magnification. Ditto, when 'pushing' magnification of the BBS charts. Using ENC charts that were derived from the original data using 'surveyors chains' and 'rods', optical instruments that could only be accurate to the nearest .2 of a degree and then 'pushing the magnification' to feet and 0.001 of a degree is ultimately going to expose you to a 'crash'.

I agree 100% with you. Over-magnification is a big no-no, and I am very careful about that. I always navigate with extreme caution anway. It might take me longer to get there by following the same routes commercial traffic would... but (knocking on wood) not a single grouding in 20 yrs of sailing.

[ssullivan]

Alan Wheeler once whispered in the wind:

OK, one final aspect that is most important. If you run aground while navigating by an electronic chart system, you are NOT covered by insurance and the electronic manufacturer will hide behind the "warning" they have printed. So maybe the chart you have is very accurate for your area, but becareful, if something ever goes wrong, it will be a sure smoke screen that all insurance parties will hide very effectively behind and you will find yourself standing out on your own.

This, I never heard before. Thanks for alterting me. I'll check into it right away.

[phorvati]

Sean,

what kind of touch screens were you looking into?

I have an Compaq Ipaq which is more like a small PDA. I was thinking about using its wifi connection to connec to my laptop which runs at the nav station hooked to the lighter plug, with opened ENC viewer and takes GPS input.

But I like the touch screen idea better. Can you tell me a bit more on the size and type and the cost.

Petar

[Lodesman]

Alan Wheeler once whispered in the wind:
The Biggest danger is NOT JUST the fact it is an electronic chart. It is the fact that a little flashing representation of your vessel is placed on top of it. The danger then, it thinking that 1: the chart placement is accurate enough and 2: the vessel placement on the chart is accurate enough, to then rely on navigating with it. There are many many cases of accidents where vessels have run aground becasue they have relied on the accuracy of the system, only to find the accuracy is fallible.
The other aspect is, I don't know how NOAA charts or the electronic primary source is derived. Here in NZ, we have a Navy Hydrographic vessel that plies NZ territorial waters and maps every square inch of it. The accuracey is umparrelled. I imagine that is why we have an inaccuraceyhere in NZ with Electronic charts. Because all the electronic mediums are produced in the US, AND if they come from NOAA sources, then they simply don't have the accuracy. Maybe US charts do.

With respect Wheels, there is no more danger in relying on an electronic plot than there is in relying on a GPS position scratched in pencil on a paper chart. If you don't back it up with mark 1 eyeball, echosounder, radar etc, you will eventually go aground.
I would also be willing to wager that NIMA/NOAA gets its NZ chart data directly from the NZHO, just as BA does. It would be anyone's guess where cmap, maptech et al. get their data from. You raised an interesting point about the insurance, but I wonder how long that will be the case. More and more hydrographic offices are pushing to convert solely to e-charts. Paper charts are too bloody expensive to produce and keep on stock. It's becoming more likely that when you buy a paper chart, it's a POD - print on demand chart, that is simply a print out of an e-chart.

I wouldn't necessarily snub raster charts - they are as good as the paper charts, if they come from a reliable source. Their drawbacks are that they can't be corrected (at least not as easily as vector) and they're memory-intensive.
I wouldn't push anyone one way or the other - you should use what you're comfortable with. But it's only a matter of time before paper charts fade into seafaring lore.

Kevin

[Rippy]

We certainly use the Mark I eyeball that Kevin mentions in his post along with dead reckoning plot, GPS fix, depth sounding and the like. All these factors help form our navigation decisions. We have never had radar and one day it would be nice, but we have got along without it for a lot of years now. It is on the list of things to buy........Ha! Right along with an Eprib, solar panels, new headsail, new sewing machine and the like......

Since the bottom conditions, depth, channel characteristics, dredging activity, and the like are constantly changing and we add a grain of salt to any chart we come across.

Good thread so far and we hope others will contribute their ideas.

Aboard SV Tin Cup

Roger Rippy

[ssullivan]

Lodesman makes some great points about navigation in general. It's actually one of my favorite parts of sailing. I guess after so many years, I forgot to break it down in detail. It's more of a 2nd nature thing now, just like sailing itself or riding a bike. Like Lodesman says... it's extremely important not to rely on any one source of information. I rely on as many as are available - charts, nav aids, depth contours, eyesight, water texture/color, landmarks, gps, compass, other boat traffic, coast pilots, radar, etc...

The key to safe navigation is to take all of these elements (and more), take all the data you can get from each, and then make an informed decision as to what heading you should be on.

As for touch screens, I was looking at some specific to Apple computers, since that's what I have. As for price... they seem reasonable until you start adding in the features you need to use it in the cockpit. You must have it ruggedized, waterproof, it should work through a gloved hand, and it should be daylight readable. A 15" display for my Mac runs in the $2000 area. Being mostly a fancy toy... I'll defer this purchase until next year.

[NoTies]

I can't see any mention here of monthly chart corrections. The hydrograher office use to issue these regularly when I worked at sea and we would then make the changes in red ink. Have seen 50 year old charts still in use and up to date.
Do they still issue chart correction data?

[Euro Cruiser]

John, thanks for sharing your thoughts on the route. And certainly nothing wrong with getting down to the Caribbean NE corner via Bermuda. If making that choice and coming S as you plan, I'd at least consider departing from the Charleston-Cape Fear section of the coast due to the shorter rhumb line, since these days the storm season seems not to be watching the calendar and may still be an issue. I also think it's a fair statement that the N American weather systems have more impact in that region than further S, e.g. outbound from N FL. You also exit the Stream quicker if departing further S, which eliminates that being problematic WRT weather. (Have you stopped at Cumberland Is. before, at the GA/FL border? That alone would lure me S before departing for Bermuda; what a treat!)

And yes, from the NE Caribbean I'd probably opt for the Central Caribbean run (vs. VZ/Columbia), seeing the sights as far as Port Antonio or even Jamaica's far W coast (which is gorgeous) before angling down for Colon/San Blas/Cartegna depending on what sounds good to you.

'Prepping WHOOSH for the S Pacific' - that gave me a good chuckle. I ask myself that question almost every day, thinking that on the one hand we shouldn't need to do much, but then get lured over to the Dark Side and begin thinking of solar panels, watermaker, etc. Slippery slope... <g>

Best wishes...

Jack

[Zach]

My faith in GPS/Chart plotters isnt all that high...

Got a big ol garmin on the big boat, and I cant tell you how many times it shows the boat being 75 feet on the dirt in ditches. Or has a marker missing completely...

They've also turned off the GPS for the area... thats not nice at all. They did it for the week of the Big Rock here in NC last year. Someone must have been betting on folks that use loran cordinates!

For inland waterways I dont think you can beat a flip book of charts that cover the grounds you are cruising, and a nice pair of binoculars that make the markers "pop."

Matching up the full size charts, that inevitably arent to the same scale... that were printed different years, with different marker numbers... is a pain.

Long distance outside I havent done. Thoughts will probably change then!

Zach

[GordMay]

Zack relates how “... many times it shows the boat being 75 feet on the dirt in ditches. Or has a marker missing completely... ”.
I could tell the tale(s) of the boater(s) who hit the marker, cause that was his entered waypoint. GPS steered him/them right to it.
Sometimes, you just can’t win ...

[ssullivan]

Zach once whispered in the wind:
My faith in GPS/Chart plotters isnt all that high...

Got a big ol garmin on the big boat, and I cant tell you how many times it shows the boat being 75 feet on the dirt in ditches. Or has a marker missing completely...

They've also turned off the GPS for the area... thats not nice at all. They did it for the week of the Big Rock here in NC last year. Someone must have been betting on folks that use loran cordinates!

For inland waterways I dont think you can beat a flip book of charts that cover the grounds you are cruising, and a nice pair of binoculars that make the markers "pop."

Matching up the full size charts, that inevitably arent to the same scale... that were printed different years, with different marker numbers... is a pain.

Long distance outside I havent done. Thoughts will probably change then!

Zach

That's true, Zach. GPS isn't very useful to find your position on a line. It's more intended to find your position in a plane or a volume of space.

Inland waterways (as you describe one) don't really require much more than a list of marker numbers and knowing the minimum depth. Other than that.... it's like driving down a road.

[Alan Wheeler]

The channel I have to navigate is about 7Nm long and in places, just wide enough for two boats to pass. At low tide, it isn't big enough for my boat. The water is murky in the channel due to the strong tidal flows and two rivers entering the channel. So you can not see anything under the surface. You have to follow the markers. There are two things the GPS does that I find invaluable. It shows me the mark position and it gives me a projected ahead course. In certain places we can have a cross current. If visability is not good, then I can place my projected course on a marker and navigate close to it till I can see it. There is little room for era, but so far the GPS has been accurate enough to keep me off the tidal banks.

[Zach]

Sorry to hear about your ditch Alan. That doesnt sound like fun!

Did one that nothing could have stopped except for better local knowledge...

Was going north up the ICW behind Camp Lejeune and ran aground. In the middle of the channel. 10mph to dead stop. My Dad was at the helm (Grin... running aground, gotta keep a tally!) I was in the process of making my way down to the engine room when we hit. The stern lifted a good foot all at once...

The ICW had shoaled up right at a little inlet, one of the 2-3 foot deep cuts that runs out to the ocean. (The sand is gorgeous white... and the water as blue as you'll see till southern florida!) To bad about the "Danger: Unexploded munitions" signs!

But anyway... wound up having to go outside the can that was laying to port to find water!

We draft 5 and a half feet, wheels being the lowest point... I'm not sure how we'll get through there since the funding has been cut for the dredging in our area.

(All this is around the Lockwood Folley inlet.)

A couple miles farther north we got blown over at a 45 degree angle by the current coming through... Got mighty close to being blown up on the sandbars to port. Thats another story entirely... Gotta keep an eye out for the confused water that catches your attention! It's bound to do something your not gonna like...

Zach