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Gps navigation advise

4K views 25 replies 14 participants last post by  smurphny 
#1 ·
Hello All-

I've got allot of experience for 1 year sailing and currently a member of OPO (Off Shore Passage Opportunities). I have the US Sailing Series "Passage Making" and "Coastal Navigation" which I will start reading soon. I'm wondering if either of these books truly address GPS Nav? ... I'm thinking not?

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MY BACKGROUND:
Within 3 years I plan to buy a boat (refit for blue water) and do some single handed sailing up the east coat of USA, Canada, Iceland, Baffin Bay. When the wife retires (5 years from now) we plan to circumnavigate. I've taken an extensive intro sailing class through the NIH Sailing Club(National Institute of Health) as well as : ASA 101,103,104.

None of the training thus far has dealt with GPS nav, I can do the chart plotting. I plan to do the remainder of my training by personal education, and hands on experience through OPO. I have daily access to Flying Scots for my weekly fix.
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... I want to buy a handheld GPS. At this point I'm thinking the Garmin 78 series. I will be doing blue water passages hopefully across most of the oceans in the next few years. I want to be an informed buyer yet reading about the units don't really seem to answer the questions, the write ups are very similar between the models.

I'm looking for advise on what GPS to buy (yet, I look at GPS as only a back up to the charts). What available info is there to learn about using it?

I guess each GPS model/make comes with specific instructions as to how to use it?? Will the one I buy come with comprehensive instructions on its use?

Someone told me West Marine may offer lectures/seminars on GPS usage but I can't find any reference to this on there web site, any comment here?

Thanks, Robes
 
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#2 ·
Well you have hit on the salient point... That the liars hold court at the moment.

You navigation will be by GPS so you are right to learn it now. You are right there's no books about it. Basically because GPS takes the crap out of navigation and it doesn't need a book, just the instruction leaflet.

Make sure your GPS can plug into a laptop so you can use better/cheaper charts than Garmin. Download CM93 off the Internet, or from a cruising friend, and download OpenCpn a free chart plotter for PC. Then plug the GPS into the Opencpn and you are off and away on a learning experience that will be the basis for all navigation.

I don't have paper charts on this boat and would never sail with anyone that uses them. They are unsafe and obsolete.


Mark
 
#4 ·
I don't have paper charts on this boat and would never sail with anyone that uses them. They are unsafe and obsolete.
Mark
I can therefore assume that you won't be sailing with the US Navy, the British RN or other major Navies/Shipping lines anytime soon. Your boat your choice, not my problem.

Robes, The GPSMAP® 78 Handheld GPS is a good unit and the price is right. The reason that the write ups are similar between models is that they all do the same thing, they calculate your position from a series of satellites and display it in various formats. If you can actually plot the Lat/Long from a Gps onto a chart that would put you in the top 5% of boaters.

Gerry
 
#3 ·
Mark (above) makes a good point - you will be doing your navigation by GPS.
Paper charts are invariably out of date - I use them for planing, the make great table top discussion / conversation pieces, not so much for actual underway plotting.

As to which hand held chartplotter to get, truthfully it just doesn't matter as long as it is at least a 12 channel WAAS receiver and has updated charts. The basic level charts most hand helds come with are more dangerous than paper chart.

For me, that means get a hand held that can use Navionic's, and make sure you DO in fact register and get updates to the charts.

That hand held will quickly become a back up when you are cruising, it might even become your third or fourth option.
I sail with a Raymarine e7d chartplotter, a Magellan hand held, my android phone with a navionics app, and my note book running PolarView and PolarCOM with full NOAA charts and a hockey puck GP.
The hand held seldom gets turned on - mostly to check speed on my dinghy. It gets stored in tin foil wrap in a zippy ( a mini faraday cage).

Note for the haters - I'm not saying charting via paper is useless, I can and do. I qualified for celestial navigation while working in the Navy on a USNS so I could stand watch (didn't have to, wanted to). Being able to plot your position twice a day is great and provides a nice boost of confidence. Carrying 400 pounds of books and charts is not within my interest groups.
 
#9 ·
Paper charts are invariably out of date - I use them for planing, the make great table top discussion / conversation pieces, not so much for actual underway plotting.
How are your electronic charts more accurate than the properly-updated government paper equivalent they are based upon?

Or, is Navionics now doing their own surveys of the world's waters, now? Goggle Maps and satellite imaging are now calculating water depths, as well?

A great example of this was discovered when I was traveling down the Intra-Coastal Waterway a few months ago. The GPS Plotter showed I was cruising on dry ground, at least 150 feet outside the waterway, but within a margin area delineated by a dotted line. I called a friend at USGS about this and he provided me with the details. Essentially, the chart was created prior to the construction of the ICW in that area. Consequently, the location revealed by the GPS/Plotter was accurate, but the charts portrayed where the proposed ICW was - not the actual location where it was eventually dredged.
Gary, if your plotter put you on dry land anywhere along The Ditch, something is very wrong, whatever charts or apps you're using are piss-poor... Such a thing can indeed happen in many places, but in using my the C-Maps my own Simrad and many other units use, and a variety of other e-charts I've used, they've always been pretty much spot-on for the entire length of the ICW... I've been placed in the wrong lane on the NYS Thruway, or on the wrong side of the railroad tracks along the Erie Canal, for instance - but I've never been placed on dry land anywhere along the US East coast, that I can remember...

Something's very wrong with your setup, that simply shouldn't be happening in the location you describe... I find it inconceivable that any modern e-charting software would be using information/surveys that pre-date the actual creation of the ICW...
 
#7 ·
I agree with most of the above. You will be using a plotter for most of your navigation, and the instruction manual is probably all you need to know how to do that. However, there are coastal navigation skills (ASA 105), that you still need to stay safe. ASA 105 does touch on GPS navigation a little.
 
#8 ·
Much of the GPS accuracy is dependant upon the latest updates of the charts held within. Some are older than Methusila, dating back to the 1950s, others are older.

A great example of this was discovered when I was traveling down the Intra-Coastal Waterway a few months ago. The GPS Plotter showed I was cruising on dry ground, at least 150 feet outside the waterway, but within a margin area delineated by a dotted line. I called a friend at USGS about this and he provided me with the details. Essentially, the chart was created prior to the construction of the ICW in that area. Consequently, the location revealed by the GPS/Plotter was accurate, but the charts portrayed where the proposed ICW was - not the actual location where it was eventually dredged.

The same is true in the ICW on your charts behind Virginia's Barrier Island. All the markers are in place, but there is NO channel - it was never dredged. So, from Oyster north to Wachapreague, the ICW may be on your charts, the same charts within your GPS, but it does NOT exist in that location. Instead, the ICW in Maryland and Virginia is essentially Chesapeake Bay.

So, the argument of paper charts V/S GPS plotter is pretty much mute - the accuracy of the charts is the same. The big difference is the accuracy of the device is far superior, often with an error factor of +/- 9-feet, depending on the number of satellites tracked at any given time.

For me, the GPS/Plotter is among the most valuable navigational tools any captain can have aboard his or her vessel. THE most valuable tool is your eyes, followed by common sense.

I use the Lowrance HDS7, and it's an incredible machine.

Good Luck,

Gary :cool:
 
#11 ·
If you can do chart plotting on paper then the GPS is easy. Most books on navigation cover GPS, but don't go into great detail. This is because it all depends on the model GPS you are using. Most GPS's will come with instructions on their use. For the most part it is very intuitive, most people who have lived in the modern electronic world should have no problem picking one up and using it. If I could sum up what most of the books have to say about GPS it would be this, always check you route, when you put in a route to a waypoint into the GPS the machine doesn't check for obstructions between you and the waypoint. You need to do this yourself.
I use a Garmin 76 handheld and it works great. There very good at showing you where you are and whats in the immediate area. There weakness is in planning and showing you the big picture. To much scrolling and zooming in and out. Paper charts are much better at showing you the big picture at a glance.
 
#12 ·
John,

Nothing to do with MY setup - it's merely a function of the input data, which is wholely supplied by governmental agencies - not the private sector. To MY knowledge, there is no private sector surveying of the world's waterways being conducted - it's just cost prohibitive. Consequently, everyone using GPS, computer based charts, and paper charts, are by and large relying on information generated by USGS over the past century.

Granted, some of this is up to date, so to speak, early 2000 data, but there's an enormous amount of information that is older than many of the forum members. John, if you have the opportunity to traverse the ICW in South Carolina, Georgia, etc..., you will quickly discover what many travelers of this waterway have. Charts, regardless of where they're generated from, are by and large, quite inaccurate. It's not the fault of the electronic gear, it's the input data.

Cheers,

Gary :cool:
 
#19 · (Edited)
John,

Nothing to do with MY setup - it's merely a function of the input data, which is wholely supplied by governmental agencies - not the private sector. To MY knowledge, there is no private sector surveying of the world's waterways being conducted - it's just cost prohibitive. Consequently, everyone using GPS, computer based charts, and paper charts, are by and large relying on information generated by USGS over the past century.

Granted, some of this is up to date, so to speak, early 2000 data, but there's an enormous amount of information that is older than many of the forum members. John, if you have the opportunity to traverse the ICW in South Carolina, Georgia, etc..., you will quickly discover what many travelers of this waterway have. Charts, regardless of where they're generated from, are by and large, quite inaccurate. It's not the fault of the electronic gear, it's the input data.

Cheers,

Gary :cool:
I understand what you're saying, and yes - I have had the opportunity to traverse the ICW thru SC, GA, etc... More than once, as a matter of fact (grin)...

I would disagree with you, in that in general, I find most of the charting to be incredibly accurate... Shoaling inlets are the obvious exception, of course, and anywhere else where the tidal ranges are larger, and the current runs strong... On Sunday morning, entering Port Royal Sound from outside from the north, I cut the corner by about 4 miles inside the sea buoy, shooting the narrow gap between the extensive shoals to the north of the very long entrance channel... As usual, I was astonished how accurate the charting of such a dynamic area remains, it was right on the money...

But again, I have to wonder what sort of e-charts or programming you're using, because in my experience, I've never seen any of them that have placed me on dry land anywhere along the ICW or its inlets (with the possible exception of a small, extremely changeable one such as Carolina Beach, perhaps) My C-Map for the waters inside Barnegat, for example, are slightly off - but anyone relying solely on e-charts in such a place, at such a scale, is really asking for trouble, anyway...

As gotd 25 suggests, that's when it's time to Look Out the Freakin' Window... (grin)
 
#13 ·
Just to add to my last post. I normally have the hand held in the cockpit with me and rely on it to give me my position. But you had better believe I have a paper chart right there next to it. I could waste a good five minutes messing around with the Garmin trying to get the big picture, when a paper chart combined with what I see on the GPS will tell me what I need to know in secounds.
I should also state that I'm only talking about the handhelds. A full sized electonic chartplotter may not have this problem.
 
#14 ·
Yes, the full-size plotters are far more user friendly when it comes to zooming in and out. Just takes a few seconds.

I also was a radioman in the Navy, as well as the ship's diver (tough job). Updated chart information came in almost daily, and when you looked at the paper charts in the nav room they were a maze of scribbled information over the original document. Nearly all of the scribbles, though, related to the ocean and approaches to harbors.

Gary

Cheers,

Gary
 
#22 ·
Yeah, I suspect anyone who's gone pretty much anywhere can offer such examples... Where was yours taken, btw?

When it happens in places known for rocks, and fog, it should really give one pause...

Damn, think of all those Newfies lying under those headstones, who might have been saved, if only they'd had the benefit of today's technology... (grin)



 
#20 ·
My primary navigational tool is, naturally, my eyes, followed by common sense, followed by my GPS/Plotter, and sometimes, I even look at the charts, which I have lots of onboard.

The area just south of Carolina Beach, where the ICW is about 100 feet wide, is where I noticed that there was a 50-foot descrepency. Also just south of Jacksonville Beach, for a distance of about 3 to 5 miles, the same 50-foot difference between the actual position and GPS location.

My Lowrance HDS7 uses Lowrance charts, and also Navionics - I prefer the Lowrance mode, which is incredibly accurate and detailed.

Fire up your GPS/Plotter and take a close look at the ICW behind Virginia's Barrier Islands from Cape Charles to Chincoteague. I think, John, that you'll find it interesting to say the least.

Good Luck,

Gary :cool:
 
#21 ·
Fire up your GPS/Plotter and take a close look at the ICW behind Virginia's Barrier Islands from Cape Charles to Chincoteague. I think, John, that you'll find it interesting to say the least.

Good Luck,

Gary :cool:
Sure, I have no doubt that particular area as charted bears little resemblance to reality...

However, I doubt that waterway - with a project depth of 4 feet or so, and probably considerably less in spots, and the 35' clearance of the fixed bridges over Chincoteague Bay - is included in what most people think of when they hear "Atlantic Intracoastal Waterway"... (grin)
 
#23 ·
It has been some time since my nav training so feel free to correct any inaccuracies I may proffer. Nav 101: Charts are flat, the earth is spheroid. Within a given chart, survey work done on the datum points give good relational accuracy which puts you pretty accurately on the chart given the bearings you take. Unfortunately, the earth is spheroid (not round or oval, but actually a little bit lumpy). GPS calculates where you are on the surface of the spheroid and not necessarily the cardinal coordinates for a given chart. If your chart has been updated to WGS 84, then it reflects this and you should have a pretty accurate fix on your (newer) paper or electronic chart. If the chart has not been updated and is showing something like WGS 72 or older, then the chart may or may not be that accurate depending upon how “lumpy” that particular patch of earth is. In the US (and most of Canada and Mexico) the WAAS system is used to ensure greater accuracy in the timing measurement. However, due to the placement and orbits of the WAAS satellites, places like the arctic, coastal Mexico (and potentially the US coastlines) may have slight variations in the timing signals and hence GPS accuracy.

GPS only “replaces” the celestial part of navigation and there are tons more to learn about navigation than turning on the Garmin and setting the autopilot. How many of us have chart #1 for example? Can you calculate set and drift? Heck, most people can’t even spell “ded reckoning” correctly. Sure, Columbus discovered the New World, but a skilled navigator will make landfall where he originally intended to go.
 
#24 ·
The wonderful thing about all the new technology that has "replaced" paper charts is that one can now get a device that displays all the information on one screen.

AIS, radar, chart plotter depth sounder, everything one needs to exactly observe not only one's own position relative to all things stationary but also to observe one's position to and the identity of the more threatening of those things moving.

There are even some of us that believe the screen on this marvelous piece of equipment will never go black, leaving one without ANY form of positional data.

The paper charts I use cannot accidentally switch off. Sure I use GPS to find the spot on the chart where I think I'm at but if I'm able to hit something then I'm also able to see it using the good old Mark 1 Eyeball.

To each his own.
 
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#25 ·
Post Disclaimer: By posting the link below I am no way saying everyone should panic, run around in circles like their hair is on fire, scream like Chicken Little, go buy the next sextant they see and learn celestial nav., brow beat those that advocate paper is a necessary back up or those that say GPS is all you need. This is squarely informational for you to use as such.

How to bring down mission-critical GPS networks with $2,500 | Ars Technica
 
#26 ·
The age of expensive, bulky, quickly obsolete paper charts is obviously in decline but even if a paper chart is obtained from your chartplotter via a printer, it is still another source of information to weigh against what shows on the plotter screen. The more sources of navigation information the better. There is always an element of DR. Confirming what you are observing should have as many inputs as possible, not just looking at a digital image which COULD be wrong for one reason or another.
 
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