Traditional or digital navigation - which is safer?

[Jim Cate]

All this worry about what if a lightning strike, solar flare, atomic explosion or civic upheaval takes out the GPS nav system on your boat... and how much safer the good ole celestial methods are.

Bull puckey!

These are really unlikely events. On the other hand, back in our celestial days we had a passage from Hawaii to SF where we had 11 straight days of heavy overcast which, of course, completely wiped out celestial observations. So, the 'safe' old method did not work at all. Overcast periods are a lot more common than nuclear EMPs, etc. I think the conclusion is obvious...

In that passage we ran DR and it got us into range of the California coast and there the sky cleared and we found that we were only around 50 miles out in our DR and all was well. The same could have been done if one's GPS based system failed. Carriage of paper charts is implied in this, and of course I do advocate such practice, at least oceanic scale coverage to allow plotting the DRs as you proceed.

So, w hich system is safer? I think modern GPS systems are far safer than celestial for a host of reasons, especially for the casual sailor. It would be great if everyone who pilots a boat was a skilled navigator and pilot, but that ain't likely. I reckon that use of the mod systems has saved far more butts than it has led astray.

Jim

[jtsailjt]

Originally Posted by Bycrick

I disagree. A GPS tells you nothing at all about where you are on any hypothetical chart. To niggle details, if the GPS system, satellites and your receiver are all working properly (which will probably be true most of the time), you will derive a position relative to an arbitrary description of the earth (WGS 84) that is most of the time within an error of a a few tens of feet. If that exercise just happens to be wrong, how will you know your calculated position is wrong? Even if it is correct, your position as shown on a chart is dependent on how accurately the chart displays information, which an unfortunate amount of the time, isn’t very good.

A simple example of hidden failure has to do with the use of True vs Magnetic bearings. Your GPS computes them as True. You’re steering compass reads out in Magnetic. Most systems will tell you that they use "magic" and can convert one to the other. But the "magic" is usually a computer model of variation vs position that’s provided by the government. It’s usually good for 5 years, but this year was updated sooner because it was wrong.

So, have you updated you plotter software to get the current model? Do you know what year's model the MFD is using? If you have multiple devices, are they all using the same model? What happens if the model is outdated? Continue using it? Just stop converting?

All electronic nav systems have these kind of issues. To assume that they’re right without being able to check them is just placing blind hope in a system which everyone knows is someday going to be wrong.

Blind faith isn’t a good navigational tool.

Variation changes very very slowly, and even if it does, your gps still can accurately tell you your lat and long and height. Also, most people don’t replace their paper carts when variation changes by a tenth of a degree and aren’t constantly getting updates about how much change has occurred everywhere they might travel.

A chart plotter or gps can certainly stop working or have inaccurate chart information, but that’s why you have 3 or 4 of them aboard, with usually only one of them dependent on the boats electrical system. Navigation by sextant is not even close to as accurate as a gps and the likelihood of your sextant becoming useless due to a cloudy sky is a lot greater than the whole gps system coming down or all of your boats gps’s dying at once. There’s no more blind faith involved in digital navigation than there is in using paper charts if you have backups and use a little common sense.

I was brought up as an old school navigator and spent time in the back seat of an F4 when the inertial only held 2 waypoints and usually drifted a couple miles an hour when pulling g’s, so I did a lot of paper chart plotting and dead reckoning while going very low/fast, and then I started sailing off the Maine coast in thick fog and unforgiving granite ledges, an interesting mix back 30 years ago. Almost every time we had a few foggy days in a row you’d hear somebody calling the USCG because they were aground. Now calls like that are much more rare. So, before digital, especially in our local conditions, you had to get good at navigating using paper charts and DR since that’s all that was available. LORAN was accurate in some places but not others so I never could trust it. Also, by the time you plotted your loran position and guessed at the local accuracy, you were somewhere else, assuming you hadn’t hit a ledge while you had your head down figuring it all out. I still fly commercially and airlines have been all digital for many years and instead use a moving map digital display that gets its position information from 3 inertials that are constantly updated by multiple gps’s and/or other ground based navaids. If one inertial doesn’t agree with the others, you get an alarm so you can take a look and figure out which is giving bad info. But it almost never happens. The same sort of multiple backup system works well on a boat. Keep cross checking 2 or 3 of them and they disagree by more than about a hundred feet, stop and figure out why. I still have paper charts aboard just because I haven’t thrown them out but now only use them because they are so much better at letting you see the big picture just due to their much larger size than a plotters screen.

[Shrew]

I do my initial planning with a paper chart because it's easier to lay out on the dining room table with a drink while I plan trips. I do the initial route planning on paper....again because it's easier to make measurements as we discuss and change out minds. I then transcribe all the routing in the chartplotter. I do keep the paper at hand in transit, but primarily (99.999%) use a digital chartplotter. Occassionally I'll use the paper to verify a marker location or number up ahead rather then attempting to scroll around the chartplotter looking for it (scoll out and you don't see the marker...scroll in and you have to 'Helen Keller' your way around the screen hunting for it.

[Pizzazz]

Digital all the way. It is orders of magnitude better than paper charts, many steps are automated, there is less chance of a casual error. Most people who do both are older sailors who have difficulty adjusting to the new technology. This was recognized early when commercial shipping was switching to digital and there was a transition period to allow pilots to build up digital navigational skills gradually. Following this transition period it is exclusively digital now.

All arguments in favor of keeping paper charts or hybrid, redundancy, etc. are moot at this point.

By the way, the same transition is happening with magnetic vs. flux gate/GPS compasses. I only carry a small backup magnetic compass that I have not used in years. But many traditional sailors who come on my boat say, it is better, but I am used to a magnetic compass.

At the end of the day, do whatever you feel most comfortable with. Digital navigation has reduced the time to plot a course, route according to weather, check destination through aerial pictures and 3D views from hours or days to minutes. This is extra time that you can use for more boat maintenance work .

[RichMac]

Originally Posted by Hoodsail

I learned to fly (single engine land) 49 yrs ago when only paper, directional finders, and your eyes (visual flight rules) were available...would say, current gps is the gold-standard, albeit moving at 100 knots not 6..

My last few flights across Australia have been without any paper! Just the legally required 2 iPads (plus 2 phones). It’s so much easier, not having to manage multiple charts and other books etc in a tiny cockpit.
I think it’s safer than traditional air navigation, but I must admit to feeling a bit lost without a chart on my knee!

[SeanPatrick]

"GPS jamming expected in Southeast [U.S.] during military exercise"

This also happened in the same area in 2019. Granted, the article states that "GPS could be affected for [...] a radius of 180 nm at 50 feet above the ground." And the elevation increases substantially the further one is from the exercise - so this is mainly an issue for pilots.


However, it highlights the fact that GPS jamming/spoofing is becoming more commonplace. And I wouldn't be surprised if people relatively near the exercise experienced at least some signal reliability issues at sea level. GPS signals are rather weak and easily interfered with.

[Bycrick]

I, for one, haven’t seen any "fear" of electronic navigation expressed here. What I’ve seen from several posters is a belief that electronic navigation systems are all one needs, and that largely from people who don’t seem to understand the limitations and possible errors and failure modes. I use electronic navigation all the time, and I wouldn’t sail without it if I had a choice. I use an autopilot almost all the time, but that doesn’t imply that I should remove my steering wheel to make more room in the cockpit for cocktail hour.

[Pizzazz]

Originally Posted by Bycrick

I use an autopilot almost all the time, but that doesn’t imply that I should remove my steering wheel to make more room in the cockpit for cocktail hour.

I have been thinking about this. Remove the steering pedestal, convert to a linear drive and steer by wire. There is always the emergency rudder in case of a failure. This will open up the cockpit significantly... could be converted into a hot tub . In the case of my particular boat it will also allow more space in the quarter berth. May be one day.

[jtsailjt]

Originally Posted by Bycrick

I, for one, haven’t seen any "fear" of electronic navigation expressed here. What I’ve seen from several posters is a belief that electronic navigation systems are all one needs, and that largely from people who don’t seem to understand the limitations and possible errors and failure modes. I use electronic navigation all the time, and I wouldn’t sail without it if I had a choice. I use an autopilot almost all the time, but that doesn’t imply that I should remove my steering wheel to make more room in the cockpit for cocktail hour.

I can assure you that all the worlds airlines are aware of and understand the limitations and failure modes of digital nav systems, but yet they use digital navigation exclusively to safely navigate all over the world. Use paper charts if you want to, but don’t assume those who make a different choice are doing it out of ignorance.

[Bycrick]

Catching up on some of the posts that I missed.

I’m not speaking of the catastrophic loss of GPS systems or nuclear war. Solar flares might be bad, but they’re rare enough not to trouble my sleep. Lightning strikes more probable, I've had two in my years cruising. But I’ll point out that there have been "hidden" problems with GPS. Bad clocks in the satellites. Or the boat GPS using WAAS, that quietly failed when the Air Force changed the satellite IDs and some GPS receivers didn’t recognize the new IDs and quietly dropped back to not using WAAS but with degraded accuracy. Several people ran aground in narrow channels. Most GPS choose the "best" satellites and use them to develop a fix. But I read several years ago about some new receivers for more critical that we’re supposed to generate ALL the fixes available and then compare them, giving a warning if they didn’t match well enough.

Variation does change slowly, but in my example if you haven’t updated your plotter or GPS unit since you bought it, do you know if the conversion from true to magnetic is accurate? If it was off by 5 degrees when you set your AP, that might be important.

We all know that the electronic chart data is neither complete nor completely accurate. Neither is paper chart data, but we're more conditioned to accept data "on the computer" as being less worthy of skepticism.

My point is not that one should be afraid of electronic systems, but that one has to know how to use them and hopefully have enough situational awareness to know when they might me wrong. If you simply buy it, install it and tell it where you want to go, you might be disappointed where you end up.

[Dsanduril]

Originally Posted by Bycrick

...My point is not that one should be afraid of electronic systems, but that one has to know how to use them and hopefully have enough situational awareness to know when they might me wrong. If you simply buy it, install it and tell it where you want to go, you might be disappointed where you end up.

You can substitute "traditional" for "electronic" in that paragraph and it is still all true. Those who take the time to learn the tools and are prepared will likely be fine, and those who don't, well, they might be disappointed where they end up.

[Bycrick]

The world's airlines and shipping almost all use purely electronic nav systems. But I submit that the system that I put on my 45’ sailboat is not an equivalent system. Even if it were, there are times when the systems don’t work the way they’re expected too, and it’s nice if the humans can know this and take reasonable corrective actions. I’ll point out the two Navy collisions and the two 737 Max crashes.

As for the unexpectedly quick response to my contrived example about removing the steering wheel, I don’t find flying-by-wire as so ridiculous. Properly engineered and with a tiller-autopilot you could attach when you were using the emergency tiller, I don’t find that at all unreasonable.

I’m not a Luddite, longing for the days of the astrolabe and a piece of magnetite floating in a bowl of water. But I’m constantly surprised by people saying "Just trust the electronics." I’ve worked with computers since 1963, developed both hardware and software, and know that none if it works perfectly all the time.

[Bycrick]

Dsanduril makes my point exactly. Neither traditional nor electronic navigation is a perfect solution. I think that saying one or the other is the only way to go is incorrect. One should use all the available tools. I have several computers and iThings but haven’t thrown away all my paper and pencils.

[Bruce K]

I remember sailing from New Caledonia to East coast of Oz in the 70's by sailing "west", its a pretty big target; about 90deg i think! 3 on board, no one wanted to navigate ( celestial); so we headed "that way", arrived not far from Coffs Harbour about a week later.
Anyone else remember a "Yeoman" navigational device? plotted from a GPS directly onto paper charts via a mouse/puck thingo, I still have the manual, but don't remember where the device went.

[Paul Howard]

I also began in the days before Satnav and GPS were commonly used in pleasure boats and greatly appreciate having that knowledge. I do use digital charts and carry paper and use paper charts, even if a chartbook, especially for more detail around islands, harbours and anchorages.

Having knowledge of manual position finding is a great asset.
Often, when using digital charts I get a 'hunch' that all is not right and double check on paper. It has saved my boat several times.