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  #11  
Old 02-02-2011
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One thing I haven't seen mentioned yet is using the DSC position function when you're buddy boating. Three of us Sailnetters kind of kept track of each other's location this past summer while cruising the same area. It's a great feature, especially if you owe one of them money and are avoiding them.
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  #12  
Old 02-02-2011
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Quote:
Originally Posted by erps View Post
One thing I haven't seen mentioned yet is using the DSC position function when you're buddy boating. Three of us Sailnetters kind of kept track of each other's location this past summer while cruising the same area. It's a great feature, especially if you owe one of them money and are avoiding them.
he's speaking from experience is my guess.
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  #13  
Old 02-02-2011
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Quote:
Originally Posted by erps View Post
???????
How does anyone get anywhere new, if they don't aim for it? Easiest way to aim for it, is to assign it a waypoint and steer towards it. I totally agree that you can't assume that your new waypoint will be a safe waypoint, but that should become apparent as you approach it.
Unfortunately, I've seen too many rookies take the waypoints in their GPS for gospel...and that's usually a bad thing. I agree you can use them i fyou remember that they're not tested IRL, and as such should be approached cautiously.

I go buoy or marker to the next buoy or marker... and keep the GPS chartplotter for the big picture, and have the paper charts out. I use the Post-It tape flags to keep the position of the boat updated on the chart, especially if I'm in unfamiliar waters.
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
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  #14  
Old 02-02-2011
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Quote:
Originally Posted by sailingdog View Post
I would point out that trip planning using a chart plotting software package is not the best idea.... using waypoints that you have not physically been to and relying on them is at best risky. You have no idea of how accurate your electronic charts are in a specific region or area, and basing actual routes on them without doing the basic research using the pilot books and paper charts is unwise.

BTW, if you think using software to get in and out of anchorages that have risks or obstructions according to the paper charts is a good idea, you might want to take up another hobby.

The information on marinas is nice, but remember it is a static snapshot in time, and marinas change hands, go out of business, and such fairly often, especially in times of economic hardship. The information found in cruising guides and charts--both electronic and paper--is often out of date by the time it is published.

Using a GPS as your only method of determining your position when uncertain is less that ideal. If you are in sight of land, using coastal pilotage skills and techniques makes far more sense, since these will locate you relative to the land, and not relative to some cartographer's electronic rendition of the actual area.

There's a reason you navigate from BUOY to BUOY... cutting corners without local knowledge is stupid and risky.

Getting depth information from an electronic chart is also stupid. The depth information isn't going to account for shifting sandbanks and shoals, and was of questionable accuracy when the data was collected, much less months or years later, when you're actually using it. Your depthsounder is a much better choice for depth data, especially since the numbers on the chartplotter don't account for tidal variation in depths.

Using a GPS to backtrack is fine, provided the accuracy of the unit at the time you do so was high enough when you made the track in and are following it out. That isn't always the case, and the more critical the navigation, the less I'd rely on the GPS. Use your Mark I EYEBALL instead. Even in fog, you can get a fair bit of information from it. For instance, if you're entering a narrow channel, say 80' wide, and your GPS had an accuracy of +/- 20' when you made it and has an accuracy of +/- 20' when you follow it out, you could be 40' from the center of the channel. That could be really bad, especially in something like the ICW, where the channel's edges are often laden with things like submerged tree stumps.

If you need to determine distance to objects over a mile away, use radar. It is very accurate for distance bearings, not so good for compass bearings.
I've pretty much used my GPS Chartplotter in the ways the OP noted. I agree that a fair amount of caution is warranted as conditions do change (shoaling ect.) but I have used a GPS track to backtrack out of creeks with skinny water, keeping a good eye on the depth sounder and constantly guessing where I might find deeper water if the depth gets too iffy.

I also regularly plot to waypoints I've never been to always erring on the side of the deeper water. I basically trust the chartplotter to get me within binocular range of what ever waypoint I'm using, and then use the MkI Mod 1 (Lasik)eyeball along with the depth sounder to confirm what the Plotter is telling me.

As for cutting bouys, there are bouys you can cut, and ones you can't. I regularly cut one coner in my new sailing grounds where the chart shows plenty of water for my boat inside the mark. Many channels are marked for commercial traffic, so there is no point sailing 2 miles out of the way when there's 10' of water inside the mark and you draw less than 1/2 of that. Cutting marks puts the onus on the skipper to know where deeper water is and take action to make sure you don't sail into areas that were shallower than you expected. Following contours is a method of managing the risk when you're unsure of the area.

The problems are really with the accuracy of marine charts rather than with the GPS system.

The GPS in my aircraft allows me to fly approaches as low as 200' AGL at over 100 mph. The lateral limits are such that if the needles are kept centered, I'll be on the centerline of the runway. Selective availability is no longer, so the problem is not positional accuracy of the GPS but the accuracy of the chart you postion is being desplayed on and the fact that the bottom can change even if the chart presents your lateral position perfectly. For me, I have a "trust, but verify" relationship with my chartplotter. I'm quite comfortable that its showing me pretty much where we are and its up to me to figure out the part the box can't know.
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  #15  
Old 02-02-2011
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This is less relevant to the use of chartplotters and software than to "being safe". Some of the best anchorages and places we visited on our cruise were due to NOT going buoy to buoy. You can't be so afraid of what your paper charts don't show you that you don't adventure at all.

Personally, while we carry paper charts as backup, I find my CoastalExplorer software to be one of the best voyage planning tools ever. With the offline ActiveCaptain integration that CE now has you can plan a week long trip in minutes and know everything there is to know about every place along the way. There is absolutely no way you can do that with paper charts.

By the way - one of the biggest issues of going buoy to buoy is everyone else doing the same thing. Always make sure that you use a point a couple of hundred feet or more off of a buoy as your waypoint. In the case of the Bahamas, where EVERYONE is using Explorer Charts, DO NOT head right for an Explorer waypoint unless you want to risk collision with the 20 other cruising boats that ARE heading right for an Explorer waypoint.

SD - with CE and most other charting software, the NOAA ENC and RNC downloadable charts will be more up to date than the paper charts you buy, unless you combine the paper charts with a bunch of NTM and NOAA corrections - and who wants to do that when you can just download the latest copy of the chart.
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  #16  
Old 02-02-2011
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Quote:
Originally Posted by midlifesailor View Post
.....The GPS in my aircraft allows me to fly approaches as low as 200' AGL at over 100 mph. The lateral limits are such that if the needles are kept centered, I'll be on the centerline of the runway.....
Agreed, however, aviation units have Random Autonymous Integrity Monitoring. Not sure if that is inherent in marine units.
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  #17  
Old 02-02-2011
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Originally Posted by labatt View Post
This is less relevant to the use of chartplotters and software than to "being safe". Some of the best anchorages and places we visited on our cruise were due to NOT going buoy to buoy. You can't be so afraid of what your paper charts don't show you that you don't adventure at all.

Personally, while we carry paper charts as backup, I find my CoastalExplorer software to be one of the best voyage planning tools ever. With the offline ActiveCaptain integration that CE now has you can plan a week long trip in minutes and know everything there is to know about every place along the way. There is absolutely no way you can do that with paper charts.

By the way - one of the biggest issues of going buoy to buoy is everyone else doing the same thing. Always make sure that you use a point a couple of hundred feet or more off of a buoy as your waypoint. In the case of the Bahamas, where EVERYONE is using Explorer Charts, DO NOT head right for an Explorer waypoint unless you want to risk collision with the 20 other cruising boats that ARE heading right for an Explorer waypoint.
I've seen this happen. A 65' lobster boat out of New Bedford rammed a large green lit buoy one sunny day as we were coming into the harbor. There was NO ONE visible in the bridge, and as soon as they hit the buoy, someone popped up and ran across to the helm. It was pretty clear that they were not keeping a proper watch and had the boat on autopilot.


Quote:
SD - with CE and most other charting software, the NOAA ENC and RNC downloadable charts will be more up to date than the paper charts you buy, unless you combine the paper charts with a bunch of NTM and NOAA corrections - and who wants to do that when you can just download the latest copy of the chart.
True, but if he is using the software that comes with the chartplotter and the charts off the plotter, that's a different story.
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
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  #18  
Old 02-02-2011
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Chartplotter vs Mapping GPS

Is there a difference between a Chartplotter and a Mapping GPS? Is there a difference in the information that they provide?

I've experienced what others have noted: It's the maps/charts that are loaded into the GPS that lack accuracy and not the Lat/Long the GPS is providing. Someone once told me many charts outside of US waters were originally made just after WWII... and have never been updated!

However, I did use a Mapping GPS for primary navigation (no boat instrument at the time) sailing from San Diego into San Francisco. We made port late each evening, stayed within 5 miles of shore, and did NOT have any navigational problems... Until, in the Suisun Slough, the GPS had us crossing land .

Like anything else, navigation by GPS requires some common sense. Oh, and actually believing what your eyes are telling you when you're NOT fixated on the tiny screen .

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  #19  
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I had sailed for years without a gps. I have been using one for less than a year now. I was very, very skeptical at first. I verified everything with charts and sight. I sail in the Chesapeake and sailed much of it last season. I continue to use other methods of navigation and always will. But I was amazed at how accurate the thing is. It is tempting to place too much reliance on it so I’m constantly telling myself not to. Perhaps because the Chesapeake is so popular for boating, the charts (hence chart plotters) tend to be more accurate than other areas of the country. Thanks for the input. SD – thanks for the 180.

One other use (but is brand specific and I’m not endorsing any brand of anything) is the integration of Google Earth with my chart software. It is amazing. I can zoom in on a marina and tell if it is primarily sail or power.
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  #20  
Old 02-02-2011
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In major boating areas of the USA, the charts, regardless of the maker, are probably going to be fairly accurate. As you get further off the beaten path...the charts will be less accurate, be based on older data, etc. However, if you get into the habit of relying on the chartplotter as "gospel", when you get into those further-off-the-beaten-path areas, it will come to bite you on your backside. IMHO, it is better to not learn bad habits to begin with.
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.

—Cpt. Mal Reynolds, Serenity (edited)

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