Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 06-01-2009, 17:33   #31
Registered User
 
Amgine's Avatar

Join Date: Dec 2004
Location: Vancouver BC
Posts: 1,384
Images: 1
MarkJ: Even if a paper chart is *wrong* (having the relatively incorrect lat/lon) it can be *right* by having the correct angles and distances (in scale) between objects.

In my experience, and so only for me, it is usually easier to visualize from a paper chart than an electronic plotter, once I have determined where I am on that chart. This is because I can see landmarks, while piloting, which relate my position directly to the chart. On a plotter at best I am relating my real position relative to where the GPS says I am, and secondarily where it says everything else is relative that. Two steps of relativity are more difficult for me than one step.

The idea that electronic navigation can be used to get a boat from Point A to Point B seems likely to A) sell more electronic gear, B) result in more boats on the rocks than the idea that a boat skipper must learn how to navigate to get a boat from Point A to Point B. It's not that electronic navigation is bad - far from it! - it's that using only electronic navigation is bad.
__________________

__________________
Amgine
Blog

On the internet, nobody knows you're a dog anchored in a coral atoll.
Amgine is offline   Reply With Quote
Old 06-01-2009, 18:33   #32
Obsfucator, Second Class
 
dacust's Avatar

Cruisers Forum Supporter

Join Date: Feb 2008
Location: Southeast USA.
Boat: 1982 Sea Ray SRV360
Posts: 1,743
Quote:
Originally Posted by MarkJ View Post
I wonder if someone puts the boat on the rocks and kills a crew member and says he was using paper charts only (though he had a chartplotter on at the helm) that he is a stickler for the old ways and likes to go below to where the chart is, that he could be charged with negligence causing death?

Asa hard copy backup to be used, fine, but a a primary nav scource? Its days must be dated?


Mark
Actually most places it's the other way around. If you are caught navigating by electronic charts alone you might be liable. Most electronic chart systems are not recognized as meeting the official requirements of carrying charts. You must have the paper charts on board to be legal.

That is, unless this has changed in about the last 1.5 years since I last researched it...

On another topic (to expand on what Amgine mentioned that I agree with totally):

Remember, the correct way to use a chart if you are within sight of land is not to determine your position by sextant or GPS and use that to decide where you are on the chart. You use land marks and take bearings to see where you are on the chart in relation to those land marks. In this way it doesn't matter what the datum was and it does not matter how accurately the chartmaker knew his position. It only matters how accurately the charter plotted things in relationship to each other. So the age of the chart mostly only makes a difference as to what may have changed.

The problems come in when interfacing between charts and a GPS. Now there are all those additional errors (datum and position accuracy) creeping in.

When in doubt, revert back to using the chart with the old methods and you eliminate a lot of problems. Only use the electronics after you have been there and know what you are dealing with.

Given those points, I think it's going to be a while before electronic charting will replace paper charts for the really knowledgeable captain.

For those of you that haven't seen my posts in other threads, don't get the idea I am anti-electronics. I have lots of it, including Nobeltec, Seaclear, Maxsea and OpenCPN. And a BUNCH of GPSs. I love 'em. But I am careful to acquaint myself with their limitations and only rely on them when it is safe to do so. I also have paper charts and a sextant...

-dan
__________________

__________________
dacust is offline   Reply With Quote
Old 06-01-2009, 18:48   #33
Registered User
 
Christian Van H's Avatar

Join Date: Oct 2008
Location: Princeton, NJ
Boat: Challenger Anacapa 42
Posts: 2,097
Images: 57
Quote:
Originally Posted by G4MJW View Post
I'm told there is a 1,000,000:1 chance or less in being struck by lightning just once in your lifetime!
I'm not sure if this was a joke or not. The chance of your BOAT being struck while cruising is MUCH, MUCH greater then being personally struck. The EMF pulse generated can take out every electronic gadget aboard, along with blowing the paddle wheel and depth transducers right out of the bottom of your boat. Keep a spare GPS in your oven...just dont bake it by accident!
__________________
www.anacapas.com

Here's to swimmin' with bowlegged women!
Christian Van H is offline   Reply With Quote
Old 16-01-2009, 18:15   #34
Registered User

Join Date: Nov 2008
Location: Washington, DC
Boat: Columbia 41
Posts: 522
The accuracy of GPS versus paper? This is a distinction without a difference. The Lat & Lon displayed on the GPS may be accurate to 10m or 50m. But the background chart on the GPS display was drafted by a human being. In fact the electronic data on the GPS display may be exactly the same as that printed digitally on the corresponding paper chart of the same date. Besides simple drafting errors, aids to navigation such as channel markers and lighted bouys may have moved due to storm conditions. Either GPS or paper charts are essential in pioliting. However, the prudent navigator does not rely on any single data source but takes every opportunity to fix his positon by the best means available.
__________________
Sam Plan B is offline   Reply With Quote
Old 16-01-2009, 18:55   #35
Long Range Cruiser
 
MarkJ's Avatar

Cruisers Forum Supporter

Join Date: Dec 2007
Location: Australian living on "Sea Life" currently in England.
Boat: Beneteau 393 "Sea Life"
Posts: 12,828
Images: 25
My thoughts are the prudent navigator should NOT be using paper charts at all.

They are a historical thing used in the past. They are neither updated, nor correct. They are stupidly slow to use even by an expert navigator compared to electronic charts and a chart plotter.

I think they will be illegal within a few years in any area that has modern electronic charting.

If someone ran over my boat killing crew and said they were using paper charts I would sue their butt off.


Mark
__________________
Notes on a Circumnavigation.
OurLifeAtSea.com

Somalia Pirates and our Convoy
MarkJ is offline   Reply With Quote
Old 16-01-2009, 19:06   #36
Registered User
 
Tempest245's Avatar

Join Date: May 2008
Location: Piscataway, NJ
Boat: 34 Sabre Tempest
Posts: 937
This has been a good discussion....I know I will now check the datum of any chart I use ...and check how my GPS relates to that chart.

At the end of the day... isn't this is all a matter of scale? If your dozens or even hundreds of miles offshore, You have GPS, Celestial, Ded reckoning etc. That will get you close to your landfall. Once coastal you have eyes, ears, maybe radar, depth, gps, charts ...and as Sam says ..use the best means available.

I was helping to deliver a boat....we were entering a natural, poorly marked inlet.
I was at the helm, the skipper was below looking at the GPS/Laptop software. He yelled up for me to turn hard to starboard.....I ignored....he yelled up again...I ignored. Finally he came up to ask me why I wasn't turning...when, I pointed to the breakers about 50 yards to starboard...and the breakers 50 yards to port..and my good depth..and flat water ahead...he said...oh..ok...hold this heading...

Sorry, I know everyone has stories ..hope you forgive me mine...
__________________
Tempest
Tempest245 is offline   Reply With Quote
Old 16-01-2009, 19:08   #37
Registered User
 
Nauticatarcher's Avatar

Join Date: Jun 2007
Location: Mooloolaba, Qld
Boat: Islander Freeport 36
Posts: 396
If Captain Cook had had a GPS and chartplotter loaded with electronic charts I doubt his Sextant and paper charts would have come out of the cupboard very often (oops he made a lot of the paper charts as he went)
I feel a lot safer nosing into an anchorage at night with my plotter going than coming in blind and trying to put a fix on a paper chart
__________________
Nauticatarcher is offline   Reply With Quote
Old 16-01-2009, 19:49   #38
Registered User
 
Tempest245's Avatar

Join Date: May 2008
Location: Piscataway, NJ
Boat: 34 Sabre Tempest
Posts: 937
No argument there....We made it into Anagada at night with the plotter... and some white knuckles....long story, good ending.
__________________
Tempest
Tempest245 is offline   Reply With Quote
Old 16-01-2009, 21:36   #39
Registered User

Join Date: Nov 2008
Location: Washington, DC
Boat: Columbia 41
Posts: 522
Pray tell, where does that pretty background come from on the GPS display? Answer: Some unlnown civil draftsman somewhere draws it up, most likely from USCG field notes and Notice to Mariners. The GPS may well very well display same CAD drawing that is used to plot (print) the paper chart.

Now concerning the reliance on a GPS alone for piloting, that seems to be a very foolish thing to do. Electricity feels more of an attraction for saltwater than most sailors feel for a land-bound wife. And both relationships inevitably result in corrosion and disfunction.

Why be so prideful? What is the cost of a chart pack compared to the full value of the boat? I have a GPS, a sextant & tables and paper charts too. It helps me to sleep better.
__________________
Sam Plan B is offline   Reply With Quote
Old 17-01-2009, 02:49   #40
Armchair Bucketeer
 
David_Old_Jersey's Avatar

Join Date: Oct 2006
Posts: 10,013
Images: 4
Quote:
Originally Posted by MarkJ View Post
My thoughts are the prudent navigator should NOT be using paper charts at all.

They are a historical thing used in the past. They are neither updated, nor correct. They are stupidly slow to use even by an expert navigator compared to electronic charts and a chart plotter.
I am saving up for a colour chartplotter , simply for ease of use - and I will admit with a touch of laziness

But I like paper charts (I also like paper books - but still get lots of info from electronic media - like CF.com )....but for me both Paper Charts and Electronic Charts share one important facet. Neither is 100% right, 100% of the time and are aids to Navigation and not a substitute to Navigating.

With a paper chart that is a concept easily understood, with Electronic I am not so sure this understanding is universal - in the modern world "computer says = must be true" can be too easily accepted, as presenting info in a neat and organised manner lends credibility - it does not ensure it. (A technique I discovered long ago when PC's first landed on my work desk - make it look good and folk don't look too closely. Add a graph or a picture and folk hardly look at the numbers at all ).

Paper charts too slow? Mmmm. I would say if that was the case the boat is going too fast or the Navigator is too slow After all, it (usually) ain't rocket science (nor Astro ).
David_Old_Jersey is offline   Reply With Quote
Old 17-01-2009, 03:27   #41
Registered User
 
James S's Avatar

Cruisers Forum Supporter

Join Date: May 2008
Location: Yemen & Lebanon... the sailboat is in Lebenon, the dhow is in Yemen
Boat: 1978 CT48 & 65ft Cargo Dhow
Posts: 5,816
Images: 139
They’re all tools.
The ones we decide to have in our tool box are a question of individual preference.

As for me..the more tools the better...I like electric tools...makes the job easier.

But unless I'm next to the store that sells them or the place that can fix them, I damn well better have some hand tools....and know how to use them, no matter how antiquated.
__________________
James
S/V Arctic Lady
I love my boat, I can't afford not to!
James S is offline   Reply With Quote
Old 17-01-2009, 07:28   #42
Registered User

Join Date: Aug 2008
Location: Vancouver Island BC
Boat: 41' Morgan Classic
Posts: 105
Quote:
Originally Posted by MarkJ View Post
My thoughts are the prudent navigator should NOT be using paper charts at all.

They are a historical thing used in the past. They are neither updated, nor correct. They are stupidly slow to use even by an expert navigator compared to electronic charts and a chart plotter.

I think they will be illegal within a few years in any area that has modern electronic charting.

If someone ran over my boat killing crew and said they were using paper charts I would sue their butt off.


Mark
GPS is wonderful, I use it all the time, but I would not leavve the dock without paper charts.

I believe to do so would be as foolhardy as leaving the dock without water in my tanks because I have a watermaker.
__________________
bytownboy is offline   Reply With Quote
Old 17-01-2009, 07:39   #43
Registered User

Join Date: Nov 2008
Location: Washington, DC
Boat: Columbia 41
Posts: 522
Now, I think the best of both worlds would be a GPS chart plotter that has a "print screen" option. There are color printers that are compatible to a laptop in size. It would be nice to be able to print the area you traversing and have that on 8 1/2 x 11 on a plot board in the cockpit. I have a Northstar GPS. Maybe there is a way to have it print. I haven't looked into that yet. Anyone actually done this?
__________________
Sam Plan B is offline   Reply With Quote
Old 17-01-2009, 08:51   #44
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2006
Location: Chesapeake Region and Maine
Boat: 42' Bob Perry sloop
Posts: 4,038
Images: 4
Quote:
Originally Posted by MarkJ View Post
My thoughts are the prudent navigator should NOT be using paper charts at all.

They are a historical thing used in the past. They are neither updated, nor correct. They are stupidly slow to use even by an expert navigator compared to electronic charts and a chart plotter.

I think they will be illegal within a few years in any area that has modern electronic charting.

If someone ran over my boat killing crew and said they were using paper charts I would sue their butt off.


Mark
Mark,

Very sorry to say it, but this is either a spoof or one of the most ill-considered commentaries in a whole thread full of inaccuracies and technical omissions. More emotion here than careful thought, based on knowledge, skills, and experience.

One hardly knows were to begin.

Paper Charts, and Electronic Charts (Raster and Vector)

In almost 40 posts, no one has bothered to differentiate between raster electronic charts and vector electronic charts. The former are EXACT replicas of paper charts -- they're just snapshots of the real paper charts, and are available free of charge from NOAA. They are regularly updated by NOAA.

The latter, vector charts, are a different thing altogether. These are what is found on chartplotters and are compiled by different entities. While there are some advantages to vector charts (smaller file size, overlay control, etc.), there are also some significant drawbacks. And, you cannot assume that they have the same accuracy as paper charts or their snapshot electronic charts, the raster charts. Some do, some don't. Vector charts must be digitized, and the quality of digitization varies considerably. Vector charts often do not contain much of the shore-based information contained in paper or raster charts. Even those from a single source, e.g., NOAA can differ. NOAA actually maintains two libraries of electronic charts: raster and vector, and strives mightily to ensure that each is as accurate as can be. Not all providers are as diligent.

The term "GPS charts" has been used several times in this thread. There is no such thing. Chartmakers use a number of georeferencing aids, including GPS, where possible. But funds needed for up-to-date surveys are very limited and, as has been noted, some areas haven't been surveyed in many years.

Datum

By default, most GPS units use WGS-84 for their base datum. Many include the option to choose other datums, where needed. Charts all have to be referenced to some underlying datum. These days, almost all charts in the U.S. use WGS-84 also.

Not understanding this business of datums can lead to grief, especially outside the U.S. I once witnessed the loss of a 70' custom sloop in the British Virgin Islands due to the failure of it's professional crew to pay attention to the difference between the GPS datum they were using and the datum of the chart they were using at the time.

Accuracy of Plotted Features on a Chart

Even assuming that the paper (or raster) chart is based on the same datum as the GPS in use -- say WGS84 -- you can't be absolutely sure that the GPS-plotted position on the chart corresponds to reality. There are lots of errors in charts used worldwide, some small, but some involving large differences beween plotted position and actual position. Many sailors in Baja have found wide discrepancies, as have sailors in the Windward Islands and in the Pacific.

That said, I've found U.S. raster charts and paper charts to be extremely accurate.

Navigation Aids


The plotted buoys, channel markers, etc. on any chart -- paper, raster or vector -- may be innacurate due to incorrect geolocation or, more likely, to the aid having been moved intentionally or not.

Additionally, there may be new nav aids and/or obstructions which are not shown on the chart -- paper or electronic. No matter how often they are "updated", it's impossible to keep up with all changes.

All These Innacuracies -- What to Do?

The prudent navigator will use everything available to ensure safe passage. This includes the Mark I eyeball -- the most important nav aid there is -- assisted by charts, compass, fathometer, GPS, radar, and other means as indicated. He/she will NOT rely 100% on electronic means, or on any other single source. To do so is the mark of an inexperienced and foolish navigator.

In the past few years there have been numerous tragic wrecks involving loss of vessel and loss of life due to incredibly stupid navigational errors. Two sailing vessels have actually run up on the north seawall at the entrance to Charleston, SC. This long seawall is well marked, and the Charleston shipping channel is wide and well buoyed. Furthermore, it is deep, and anyone paying attention to the fathometer would know they'd strayed from the channel long before it would be possible to hit the seawall.

I apologize for the long post, and hope I haven't offended anyone. But navigation is a serious matter and there's an awful lot of bum information out there.

Bill
__________________
btrayfors is offline   Reply With Quote
Old 17-01-2009, 09:08   #45
Registered User
 
Christian Van H's Avatar

Join Date: Oct 2008
Location: Princeton, NJ
Boat: Challenger Anacapa 42
Posts: 2,097
Images: 57
BTray, is dead on in his post. I thought Marks post was a gag at first too. Hey Mark, do you count all those nice hand drawn charts in the cruising guides too? Some of the responses here are hard to believe...and shouldn't be believed. BTW Mark, post us when you find a way, any way, for a paper chart to cause a collision with your boat...
__________________

__________________
www.anacapas.com

Here's to swimmin' with bowlegged women!
Christian Van H is offline   Reply With Quote
Reply

Tags
charts, navigation

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Paper Charts wanted stillbuilding Classifieds Archive 1 19-12-2008 23:09
PAPER CHARTS ed stewart Navigation 11 19-02-2008 20:23
Used Paper Charts Quercus Classifieds Archive 0 15-01-2008 13:01
Looking for paper charts ess105 Atlantic & the Caribbean 2 12-04-2007 19:15
Used paper charts available Bob Navigation 1 30-07-2003 02:43



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 19:47.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.