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GPS - Whatcha got?

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Steve Milby
Past Commodore

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USA
5895 Posts

Response Posted - 01/30/2008 : 09:58:22

A gps that is accurate to within 15 feet or so is sufficient for navigational purposes. A chartplotter is great because it's easy to use, but any old gps that gives you the longitude and latitude will provide your position, and you can mark that point on a paper chart. With even the cheapest gps, you can plot your trip from mark to mark, and, if you follow the directions indicated by the gps, it'll take you there. If you use your gps a lot, then you should get a chartplotter, but if you only use it once a year, when you trailer your boat someplace on vacation, you can get by just fine with an entry-level gps. Whether you have a chartplotter or not, you should always have a paper chart for the cruising area, in case the gps screen goes blank.

Edited by - on

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 01/30/2008 : 11:48:32

You could also look at it as "the less familiar the water, the more useful the chartplotter for staying out of trouble." Around here, the rocks are right where you'd think they aren't. You can see them coming and you know where you are on the chartplotter--you're sorta guessing on the paper chart.

Edited by - on

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 01/30/2008 : 12:16:17

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Deric
 I have been advised by others to get a gps with extras: speedomter, depth finder, compass, chart plotting.

I am considering the Humminbird 383c. Has anyone have any thoughts regarding the device?...Deric<hr height="1" noshade id="quote"></blockquote id="quote">
Hi Deric... Looking at the specs, I wonder if the 383c supports Navionics charts (that other Humminbirds support or come with). No mention in the specs I saw.

I got a cheap Garmin fishfinder to go with a mid-sized (276c)chartplotter, so I have two screens--a high-resolution one for the chartplotter and a low-res bottom picture, rather than splitting one larger screen for both. It seemed like more bang for the buck at the time.

Higher screen resolution is helpful for chartplotters--much more so than for fishfinders IMHO. Try to make some comparisons in a store, rather than on websites--you'll see the difference. And remember to check the charts that are included or supported (and the cost for the latter)--the standard "base maps" generally show you navaids, but not depths, rocks, or other stuff you see on charts.

BTW, all GPSs give you speed (over the bottom) and your direction of movement (not which way the bow is facing).

Edited by - Dave Bristle on 01/30/2008 12:18:16

Deric
Captain

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USA
408 Posts

Response Posted - 01/30/2008 : 18:15:19

Hello Folks,

Very informative thread. Thank you. I still have time to continue my research about GPS devices. I do like the idea of having two devices: one as the GPS, and another as the fishfinder. I fugure I have at least three more months before I need to purchase.

One important advice to heed is to have a paper chart as well.
Someone mentioned earlier mentioned that the 10K GPS system that tracked within 2 centimeters was typical for survey work. That is correct. The person who presented the different GPS systems at our sailing club meeting is not only a sailor, but also, a surveyor.

I shall continue to monitor the thread. Thanks for the comments.
- Deric

Edited by - on

tchowes
1st Mate

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USA
36 Posts

Response Posted - 02/01/2008 : 18:25:27

Great thread. I've had an original Garmin 76 for 4+ years. I'm sure there are threads where to mount a larger GPS. The basic 76 makes a great backup. Love the ease of use with the Garmin.

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Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 02/01/2008 : 20:14:12

Another point about paper vs. electronic: when all that data is converted to vectors for electronic charts, mistakes happen. Decimal error, digits dropped. data missed - it is common to all vector charts, and since it is random error, the discrepancies vary by different chart providers. Practical Sailor compared a several products with known obstructions and found a variety of mislocated or totally missed hazards with all brands and no consistent pattern between brands. My Garmin gpses may be reasonably accurate (they do give error circles), but it doesn't help if Battery Park Marina is nearly a quarter of a mile from the water in Battery Park. I am currently berthed in Sabine Marina, but a fix from my cockpit shows me solidly aground - Little Sabine Bay doesn't exist in the Garmin database!

Edited by - on

Turk
Admiral

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USA
736 Posts

Response Posted - 02/02/2008 : 07:09:52

I needed a simple solution to finding out my speed during racing. I really wasn't looking forward to cutting a hole in the bow to mount a knot meter so I went with this:Foretrex 201

I strap it to the tiller and it has a read out in knots that fills it's entire screen. You can find it for about $89 on the internet.

Edited by - Turk on 02/02/2008 07:12:01

GaryB
Master Marine Consultant

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USA
4303 Posts

Response Posted - 02/02/2008 : 07:31:02

I've been toying with the idea of taking some large hose clamps and strapping my Garmin GPSMAP378 to the tiller. It would be the perfect location for a GPS because it's alsways at hand and close enough for my old eyes to see without my glasses.

Edited by - on

Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 02/02/2008 : 13:18:37

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by GaryB
 ...strapping my Garmin GPSMAP378 to the tiller. It would be the perfect location for a GPS because it's alsways at hand and close enough for my old eyes to see without my glasses.<hr height="1" noshade id="quote"></blockquote id="quote">...but upside-down half the time.

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glivs
Admiral

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USA
836 Posts

Response Posted - 02/02/2008 : 14:25:45

Dave B.
That type and magnitude of error sounds suspiciously like your GPS is not matched to your chart datum. Wouldn't hurt to verify your GPS settings.

Problem with locating submerged obstacles, i.e. rocks, cribs and other nasties, around here is not so much a GPS issue as understanding how the coasties place the navaids. Last falls lower than normal water levels presented a great education. I never before realized that buoys may be located several 10's of meters away from the actual obstacles. I assume this is done along the entrances of protected coves to direct traffic on the open water side, although boats seeking anchorage inside the coves better have their depth sounders and water brakes working.

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GaryB
Master Marine Consultant

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USA
4303 Posts

Response Posted - 02/02/2008 : 19:05:38

Dave

Maybe, maybe not. The unit has an automotive mount that is basicly like a bean bag but with a bendable metal plate inside (https://buy.garmin.com/shop/shop.do?pID=806). Almost feels like lead. My thought was to bend the tabs of the mount around the tiller handle and then use hose clamps with rubber protectors (similar to the type for holding wiring bundles in place) around the bean bag mount. It may not work but is worth a try.

If this doesn't work the unit also comes with a small mount (https://buy.garmin.com/shop/shop.do?pID=862)that can be mounted to almost anything with an adhesive pad (https://buy.garmin.com/shop/shop.do?pID=8022). I have one of these in my other car that has never budged in four years of driving. I've tried pulling it loose and short of using a big screw driver to pry it loose it won't budge.

Actually now that I've been looking into this a little more this evening I think I may go with the stick-on mount. I don't know what type of adhesive they use but it is extremely strong. I would still be able to get the tiller cover on and with this type mount I can quickly disconnect the GPS from the mount without having to unscrew hose clamps.

Edited by - GaryB on 02/02/2008 19:50:39

Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 02/02/2008 : 20:47:37

gliv - No, not a datum mismatch, just common errors in electronic charts. That is why I mentioned the PS review - be careful with vector charts. 99.+ % of the time they are completely reliable, but you don't know if something has been missed until you hit it. Raster charts are simple scans and consequently have all the data, but they are a pain to use and defeat the real benefits of vector charts. Paper charts have been around long enough for most things to be hit and located, and as vector charts continue to be revised and updated I am sure they will eventually be as accurate.

PS compared charted obstructions to vector charts in several areas on the east coast and Florida and found that while they were generally very good, every manufacturer missed or misplaced a few obstructions. My two errors are rather glaring, but they are there. Little Sabine Bay is immediately west (maybe 100 feet) of the causeway leading to the Gulf Breeze - Pensacola Beach bridge. Check your chart and let me know, it would be interesting. 30.335N, 87.1447W I don't search for errors, I just came across these two by accident with no il-consequences.

Edited by - on

Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 02/02/2008 : 22:23:36

gliv: not sure of your input format this is ddºmm.mm - 30º20.01'N 87º08.67'W And Little Sabine Bay does exist on NOAA enc charts, which is comforting since I am berthed there.

Edited by - on

glivs
Admiral

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USA
836 Posts

Response Posted - 02/07/2008 : 06:50:10

Dave,
Apologies for not responding...out of touch these past several days.

The issue you bring up is interesting. Nothing I can add...but certainly will pay more attention too. Thanks for noting this.

Edited by - on

Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 02/07/2008 : 07:04:34

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by glivs
 Dave B.
Problem with locating submerged obstacles, i.e. rocks, cribs and other nasties, around here is not so much a GPS issue as understanding how the coasties place the navaids. Last falls lower than normal water levels presented a great education. I never before realized that buoys may be located several 10's of meters away from the actual obstacles. I assume this is done along the entrances of protected coves to direct traffic on the open water side, although boats seeking anchorage inside the coves better have their depth sounders and water brakes working.
<hr height="1" noshade id="quote"></blockquote id="quote">

The trouble with locating and charting underwater obstacles around here are that the ice fishing huts never go through at the same place twice, the snowmobiles get a little further out each year, but they stil don't replace jet ski's (Apparently you can go about a mile on open water if you get the balance and speed just right), and the trucks that go through just aren't marked on the maps.

Sailing on a lake famous for ice fishhing has its challenges...

Edited by - on

tinob
Master Marine Consultant

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USA
1883 Posts

Response Posted - 02/07/2008 : 13:26:06

My first GPS was a Magellan. Worked well for a while then succumbed to Y2K. Magellan tried to assist me in my plight but after a while I had had enough and switched to Garmin. At the time the mod.# 48 was number one and has proven itself worthy of my support over time. Though I've been tempted to switch to larger screen units the likes of several proffered here, I'm mindful that it has never failed me in the last eight years, so why switch. I'm not going anywhere of significance, just the Great South Bay, it's enough for me. Perhaps when the boys are out of college there will be some surplus monies around but I'll be 87 years of age and unable to see anything smaller than BIG BEN. I'm locked in to the # 48.

Val on the hard DAGNABIT, #3936, Patchogue, N.Y.

Edited by - on

JohnP
Master Marine Consultant

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1520 Posts

Response Posted - 02/08/2008 : 09:40:06

Prospector,

Your ice fishing shack story reminds me of one time when I "discovered" the stack of a tug boat sunk long ago off the southern tip of Prudence Is. in the Narragansett Bay on my friend's C25. Apparently enough boats have hit it since then that it has been added to some charts.

And there is a VW bug somewhere in the water near my marina on the Magothy River. One winter the creeks, rivers, and part of the Chesapeake Bay froze hard and folks were taking advantage of the rare event by driving out on the ice. That's not marked, either.

How many snowmobiles and trucks and shacks litter your shallows? What lake are you on near Toronto? A little one or a very big one?

Edited by - JohnP on 02/08/2008 09:41:40

Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 02/08/2008 : 10:58:18

We are on Lake Simcoe - a fairly big lake.

http://sailgeorgina.googlepages.com/Aerial.jpg/Aerial-full.jpg
http://maps.google.ca/maps?f=q&hl=en&geocode=&q=Sutton,+ON&ie=UTF8&ll=44.341345,-79.365749&spn=0.044627,0.080338&t=h&z=14&om=0

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Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 02/08/2008 : 12:03:47

Beautiful area! We did the Trent-Severn a few years ago with friends on their power boat (they do have their uses). Among the most memorable trips I done. New York has invested a lot in the Erie Canal and it is a very nice trip, but the scenery can't compare to the upper Trent-Severn.

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Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 02/08/2008 : 12:25:57

Are our org. masthead or boats big enough to have Catalina 1000/11111010? Did I do that right?

That's enough for me.

Edited by - on

Dave5041
Former Mainsheet Editor

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USA
3758 Posts

Response Posted - 02/08/2008 : 15:59:52

oops wrong thread

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 02/08/2008 : 16:11:56

...answer on the right one.

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Prospector
Master Marine Consultant

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Canada
3159 Posts

Response Posted - 02/08/2008 : 17:44:31

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Dave5041
 Beautiful area! We did the Trent-Severn a few years ago with friends on their power boat (they do have their uses). Among the most memorable trips I done. New York has invested a lot in the Erie Canal and it is a very nice trip, but the scenery can't compare to the upper Trent-Severn.
<hr height="1" noshade id="quote"></blockquote id="quote">

Thanks Dave - we think our lake is a good spot to learn a thing or two. One of our goals for the coming summer is to drop the mast, navigate the upper trent to Trenton, Ontario (not New Jersey

) and tour the Kingston/Thousand Islands area. That Failing, we'll be forced to go the other way and do Georgian Bay and the North Channel.

We aren't at an exotic location, and our season is a lot shorter than other folks' but we have some nice spots that we can reach.

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John Russell
Master Marine Consultant

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USA
3444 Posts

Response Posted - 02/08/2008 : 17:48:48

<blockquote id="quote">quote:<hr height="1" noshade id="quote">We aren't at an exotic location, and our season is a lot shorter than other folks' but we have some nice spots that we can reach.<hr height="1" noshade id="quote"></blockquote id="quote">

All things are relative. Have you ever been to Trenton, NJ? You're pretty exotic -- just cold and exotic.

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 02/08/2008 : 20:48:40

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by John Russell
 All things are relative. Have you ever been to Trenton, NJ?<hr height="1" noshade id="quote"></blockquote id="quote">Well, Trenton is a lot closer to New York Harbor, Long Island Sound, Fisher's Island Sound, Mystic, Watch Hill, The Narragansett, Block Island, Cuttyhunk, Martha's Vineyard, Montauk, Shelter Island, Mattituck, Port Jefferson, Oyster Bay,.........

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