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Old 07-10-2010, 22:34   #136
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IMHO if you have more than one nav aid at your disposal, use it/them. This is a case of more being better. Charts+plotter+GPS+Radar+Sextant and reduction tables and timepiece or radio time confirmation+your own eyes+instinct+luck are a great combination and should all be used simultaneously, if possible. It is a satisfying feeling when they all agree. Even then you might not keep her off the putty. Regarding Markj's disorienting bus trip, which side of the road was the bus traveling on?
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Old 07-10-2010, 23:12   #137
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I think this thread is conflating 2 issues that are related but separate:

1) the use of a chart plotter vs paper charts to represent the area around you while underway.

2) determining where you are relative to all the hard and pointy things around you.

In 1) the use of a chart plotter strongly implies but does not require the use of a GPS to determine your position. Assuming a GPS is the source navigation functions procede very rapidly and with minimal effort required on the part of the user. Paper charts are not subject to power failures. Both are susceptible to salt water.

In 2) Significant portions of the world are well mapped with respect to one of the datums most GPS units carry loaded and GPS positions on a map will corrospond very closely to the real world. On the other hand many areas are not. Somebody (gosailingnow?) mentioned maps being in error by up to 5nm). In error compared to what, WGS84 datum? If the map was drawn to a sextant/astronomical datum which assumes a spherical earth the GPS is going to be in error to the map because it does not pick the correct datum to referrence. Almost all maps are very good at showing the correct relative positions of visible objects and so confer the utmost trust when positions are established by site and to a certain extent by radar. Maps vary in how good they represent the position of things relative to the world at large, ie lat/long.

Reliability issues aside, the chart plotters will have the advantage in areas that are well mapped to a GPS datum.

Paper charts have the advantage when datums are not so good.
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Old 08-10-2010, 06:22   #138
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Chart Errors - Paper vs Electronic - Raster vs Vector

Some of you have already seen this. But for those of you who haven't, here is a link to my take on chart errors.

--> Inland Waters Resources - Chart Errors

The concluding statement is:

"My point is that electronic charts can only be used safely if you have a good working knowledge of how to use paper charts, and you know what the additional problems are that creep in when adding electronics into the mix. I STRONGLY believe this!"

-dan
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Old 08-10-2010, 06:22   #139
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Old 08-10-2010, 07:28   #140
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Since the paper charts are not only passe but also junk, and roughly speaking in 10 years they will completely disappear from the boat, does it make sense for me to stick to my collection of 500+ charts for another say 20 years and then sell them at Christie's?

I say do not throw your old charts overboard yet, there might be a collectors rara avis in between the musty sheets.

Alternatively, does anybody know where I can find drawings for a simple furnace that I could use to burn paper charts so massively discarded by sailors nowadays (25 USD apiece). Maybe I could rig it into our hot water boiler somehow?

barnie
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Old 08-10-2010, 09:17   #141
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does it make sense for me to stick to my collection of 500+ charts for another say 20 years and then sell them at Christie's?

barnie
Dunno. Check your drivers license and see if it has your age on it...
What will you be able to do with the money in 20 years? Get the nurse to rip her kit off?

Might be better to flog them now so you can drown your sorrows a the Disco dancing on tables....



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Old 08-10-2010, 09:53   #142
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Alternatively, does anybody know where I can find drawings for a simple furnace...
Drawings for a simple furnace are so 2003. Would you like some digital 3D steroscopic CAD renderings instead?
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Old 08-10-2010, 10:05   #143
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Reliability issues aside, the chart plotters will have the advantage in areas that are well mapped to a GPS datum.

Paper charts have the advantage when datums are not so good.
The exception to this would be a chart plotter with radar overlay. When I'm in an area where the datums are off, the radar will quickly confirm that the object charted at point A is actually over there at point B.

That sort of calculation is possible by plotting radar bearings on a paper chart, but it's time-consuming and will never be quite as accurate as how it shows up on the overlay.
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Old 08-10-2010, 11:51   #144
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... Alternatively, does anybody know where I can find drawings for a simple furnace ...
Simple furnace ...
Simple furnace for high temperature nuclear magnetic resonance experiments
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Old 08-10-2010, 17:59   #145
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never leave port without them,why you ask?? if you were to take a lightning strike even though you may have a lightning protection system,the emp,thats electro magnetic pulse is likely to fry youre electronics,you do have a surge aresstor on the antenna cable right ???
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Old 08-10-2010, 19:05   #146
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LOL

To Mark: well, in 20 years I will be sixty and working very hard. I retired early.

To Gord and ActiveCaptain - THX! Finally a simple project to keep me busy over the winter!

;-)))
barnie
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Old 11-10-2010, 22:37   #147
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Further to my comments I found this link to the Australian Hydrographic Service with some good info about charts...obviously slanted to the Australian context but they raise some valid points.


Australian Hydrographic Service - Fact Sheets

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Old 12-10-2010, 08:55   #148
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Reliability issues aside, the chart plotters will have the advantage in areas that are well mapped to a GPS datum.

Paper charts have the advantage when datums are not so good.
Sorry absolute rot, in general since almost all current digital charts are derived from paper . any errors present will apear in both paper and digital, these include, mis alignment, missing features, incorrect rendering,etc. It matters not whether its a chartplotter or a paperchart one is not any better then the other when errors are present in the original survey.

There is a mis-up between Geodetic datums and digital charts, modern datums allow GPS derived locations to be refernced to charts , digital or paper, datum errors exist in both ( see Garmin).

ITs a nonsense statement to suggest that paper charts are better when datums are not so good, the resulting posiiton errors will be there irrespective of the position fixing method used. All that GPS has reveled is that previously hidden errors due to sextant error are now visible usuing GPS. If you wish treat a GPS fix with the same precesion as sextent fixes are all datum problems disappear.

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Old 12-10-2010, 09:46   #149
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Lets try looking a this in other ways;

1. What takes up more space (@ a premium in small boats)? Maybe a bunch of charts which fit under the bunk do not intrude as much as the laptop/cables for electronic.

2. Which is least intrusive on your day to day lifestyle - a chart which you drag out for planning or plotting or the computer. The plotter stuck in the cockpit a poor second cousin in this.

3. Which has the potential to most thoroughly screw up your lifestyle, cruise or weekend sail?

4. Which is more conducive to a happy partner relationship - a chart to be shared in the bunk or a screen to be jammed up on your midriff which the other half cannot focus on?

5. Which system has the least cost and requires the least $$ to get out there sailing?

6. Which system is the most reliable to get a quick answer from in 10 seconds (on some occasions that is all the time you have)?

7. Do all people see the reality of sense and direction reflected in the same way? I suspect some find the context of a chart more "real" than a screen.

Different answers from different people I am sure. But some issues to keep in mind.
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Old 12-10-2010, 09:53   #150
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Actually, I think what was meant by paper charts being better when the charts are not in agreement with GPS positions - is that you use the paper chart as a visual guide to the relative positions and locations of hazards such as land and underwater obstacles. you ignore the Lat/Long's on the chart and visually recognize that that obstacle is about "that far" in "that direction" from the beach/mountain/landmark.
- - Normally the land/underwater charted positions are reasonably accurate in relation to each other. What is not usable is to plot a GPS position on the map using the map's Lat/Lon scales. South Georgia Island in the Atlantic was the famous 10nm error when GPS and chart Lat/Lon's were compared.
- - Charts uncorrected to WGS-84 typically exhibit an average from dead-on to 1.5nm offset when plotting positions due to differences in the Datum used.
- - I problem with chart plotters is the presentation of the chart and the need to zoom in/out to see "all" the stuff that is shown on a paper chart. I like the looks of a paper chart with its little villages and landmarks, detailed shorelines, and graduated color tones. Vector charts are too "hard" and lack the subtle graduations that paper charts present.
- - The best combination is to have raster charts available for your computer nav program that can print out interested portions of the chart for use during a particular voyage.
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