The Offshore Voyaging Reference Site

11 Tips for Safe Navigation With Phones and Tablets


We updated and added to this chapter in January 2023.

As so often happens, I was inspired to write this post by the comments on a previous one: my rant about modern poorly-designed and hard-to-use marine electronics.

The consensus in the comments was that dedicated marine electronic touch screen devices are difficult to use and overpriced in comparison to general use tablets and phones, particularly those from Apple.

And, further, that many people are using phones and tablets for primary navigation.

Since I’m a longtime Apple user—I was an Apple dealer way back in 1984 when the first Mac was released—and fan of all things Apple, I was not surprised. And, in fact, I have already recommended the iPad as a backup navigation system, particularly for those who decide to cruise without paper charts.

That said, as an electronics technician by trade and an experienced navigator, I’m also deeply worried about this trend.

So here are my thoughts on some of the dangers of using phones and tablets for navigation, together with some tips to reduce the possibility of an iThing-enabled wreck:

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Bill Wakefield

Hi John,

Another great topic that isn’t addressed often enough in my opinion.

We, too, are long-time Apple fans, and we also use iPads for back-up navigation, casual route planning, for mirroring/controlling our B&G Zeus MFD, among many other things.

I absolutely concur with all your points, and I’ll add a couple of other considerations I [and I’m sure many others] can share from first-hand experience having both iPads and an MFD on-board.

[Following is an excerpt from one of my blog posts on this very same topic that includes some additional experiences that may be of interest:]

Please remember that this post will likely become dated/obsolete in a few short years as the current iPads we all enjoy are replaced with new products that may not suffer from these same issues…

First, we love our iPads, but we had several experiences over a couple of summers of full time sailing that convinced us not to rely on them as our primary or only nav/radar system/screen at an outdoor helm position: [We also have an indoor helm where we think the iPads- properly encased and mounted- are sufficient as primary screens…]

Our primary navigation [and RADAR] system is Navionics running on B&G Zeus Touch MFDs. The other primary system is OpenCPN running on a laptop. We supplement with one generation 3, and two Gen 4 iPad Airs on-board [One is a mini.] This post is mainly related to our gen 4 iPad Airs. [But the results were the same with the Gen 3 unit as well…]

iPad issues we have experienced:

-The iPad screen isn’t easily viewable in bright light- sometimes even when shaded under the dodger/bimini…

Additionally, sometimes the plane of polarization of various sunglasses is not parallel to the plane of the iPad screen, so you have to tilt your head or the iPad to see the screen.

The MFD is designed to be viewable in bright sunlight and isn’t as sensitive to polarized sunglasses.

-iPads used as a mirror to the MFD or as a stand-alone nav device need charging if in use for more that a couple of hours, and the waterproof cords/plugs aren’t really… And having charging cable(s) dangling around the cockpit is just asking for trouble and/or to be broken at the connection with the iPad… Also, those cables don’t hold up well to UV or the elements, and still don’t have waterproof connections …

This is not an issue with the MFD.

Side note: Be sure to use a USB charging source that is greater than 1 amp output [we found 2+ amp units are sufficient] or the iPad battery on our models will actually loose charge during the day when used for live navigation or as a mirror to the MFD- even though it is plugged-in… [We use readily available 2.2 amp output USB adapters that plug into our 12VDC power outlets.]

-The iPad overheats [yes, even in Alaska…] typically when in direct sunlight- especially when fitted with a waterproof cover… When this happens the screen goes black and a small message tells you it is too hot and will not be usable until it cools down [which usually takes 20-30 minutes after we physically relocated it to the shade…] This happens to us more often that you might imagine, and often when you need it most… For us, that is reason enough not to use them as primary screens outdoors.

This doesn’t happen with the MFD.

-It is difficult/impossible to rely on hearing any alarms [e.g., AIS, depth, etc.] sounding via the iPad speakers when they are in a waterproof case, or even if they aren’t when there is a bit of ambient noise from the wind, engine, etc….

Not so with the MFD- especially since it can be optionally connected to external alarm sources.

-If the waterproof case has a film covering the screen, that can sometimes desensitize the touchscreen, and sometimes reduce screen clarity due to glare or bubbles between the film and iPad screen.

Not an issue with the MFD.

These are a few of our first-hand observations and experiences that have led us to our conclusion that [for us] iPads are not acceptable as the primary or only MFD/Navigation/Radar/AIS screen on deck…

With all that said, we do use iPads at the outside helm, on deck, and down below, and love the flexibility and redundancy they provide- especially when we can hand one to guests and let them track our progress and ‘look around’ the charts without impacting the primary Nav system…

Best regards to all. Bill

Marc Dacey

Very good points, all, particularly to turn off all the “parasitic” programs you don’t need offshore. While I am unlikely to go back to the world of Apple for many reasons unrelated to the quality of the iPad, most of these tips apply to any consumer-grade device one might wish to have aboard for ease of use or as an extension to something made for the purpose. I like the idea of tablets as repeaters via Bluetooth or on-board wifi for a PC/MFD/blackbox-generated display. I agree particularly however with the observation about night vision…even young eyes don’t dark-adapt quickly enough after a dazzling to work properly…most dirt-dwellers have no concept of how dark night can be offshore, nor how bright the stars are on a moonless night, nor how even a penlight in the saloon can actually cause pain to the watchstander. Of course, none of these aspects are considered in the way a tablet or phone is lit.

Bill Attwood

Hi John.
I don’t use electronic navigation, period.
Allow me to borrow that word from the White House press secretary.
I use paper charts and I correct them – really easy today with internet access. When I read about all the things that you warn about above – and almost all comments about electronics on boats seem sooner or later to degenerate into war stories about what went wrong – I wonder why paper charts and their use has such a bad press. Do I sense an opinion that people like me are seen as dinosaurs or elitist – you shouldn’t think of going sailing unless you can navigate in “the old way”. I see nothing elitist in expecting that sailors should be able
to navigate using the basics. It may mean putting time in doing courses, sailing with others etc. Making it easy for people to go offshore with: steering wheels, dashboard instruments, rally help in case something goes wrong, emergency services prepared to risk their lives if the people need rescuing – I don’t want to go on, I’m sure you have got my drift.
Apart from a depth sounder there is really no need for any other electronics on board. Nice to have are AIS and radar. Even weather info at sea is of questionable value – once you are off soundings the weather will be what it will be. Our yachts aren’t fast enough to move out of the way, and local observations give good enough warning if bad weather is on the way.
Sorry to verge on a rant.
Yours aye

Richard Hudson

Hi Bill,

I admire people who navigate only with paper charts and traditional instruments. I admire people who sail engineless (not your point, but somewhat similar in my mind). Both types of people add an additional challenge to their sailing activities that I, as well as most people, don’t.

I agree with you that everyone cruising should be able to navigate with paper charts. And, as John said in one of his many excellent points in the article, those who don’t navigate frequently with paper charts are likely to be slow in getting back to using them.

I used paper charts as my main navigation method until I wanted to stop at an island and realized I had screwed up and didn’t have that chart aboard. I had a GPS hooked to a computer with OpenCPN and a copy of the CM93 “demo” charts of the world which float around the cruising community, which had come with the boat. So, we went to the island using only the computer for navigation–my first time entirely not using paper charts. While still not wanting to rely on the computer for navigation (I’ve experienced total electrical failure at sea in another boat and am familiar enough with non-sealed electrical connections in humid, salty environments not to be overly trustful in them), I started liking it.

I also liked how, coming into an unfamiliar port, especially when singlehanded, I wasn’t having to take bearings and plot fixes to ensure I was in safe water–I just glanced at the computer screen and it showed me where I was–that was fantastic!

On other occasions, finding myself changing plans in remote places where charts could not be bought, I came to like computer charts even more–I already had electronic charts of the world aboard, and, if I met up with another boat that had better paper charts of the area, I could take photographs and turn them into digital charts (note that this is an involved process, which requires software and practice, so most people don’t do it).

So, over time, I have come to really like electronic charting–it enables me to go more places and reduces my tension when entering unfamiliar harbors. I still carry a lot of paper charts (but not detailed charts of the whole world), and use them extensively offshore, but my navigation computer is the main navigation method when near coasts.

> Nice to have are AIS and radar.
I agree, they are nice. A sailboat only needs wind and water to sail, but for avoiding traffic and navigating in poor visibility, AIS & radar are very, very, very nice.

>Even weather info at sea is of questionable value – once you are off soundings the weather will be what it will be. Our yachts aren’t fast enough to move out of the way, and local observations give good enough warning if bad weather is on the way.

I find that lack of weather information limits options. A simple downwind, tradewind passage (outside of hurricane season) is likely to be completed safely with or without offshore weather information. But, if part of your passage involves a strong ocean current, it is really helpful to have a forecast indicating you’re heading for a strong-wind-against-strong-current situation so you can get out of the current or heave to and wait for a favorable wind to cross it. Crossing (or sailing with) an ocean current offshore without weather forecasts certainly can be done–sailors have done that for centuries–but if a strong wind goes against the strong current, sometimes people die.

If one doesn’t have weather information, one should avoid strong ocean currents. If one doesn’t have a radar and know how to use it, one should try hard to avoid fog, including avoiding places that often have a lot of fog (as Colin recently mentioned in his excellent articles about fog).

In summary, I certainly do not find sailing without electronics to be only for “dinosaurs or elitists”–but I do find that it limits one’s options. I also feel that users of electronics need to still be capable of getting to a safe port if the (primary) electronics fail.



Hi John,

A very good summary as always I would say, thanks.

I normally use two completely independent electronic chart systems (2 computers + 2 GPSs with even independent battery power) and a paper chart as backup for primary navigation.

But having said that, I sometimes have not updated my electronic/paper charts with the latest notices to mariners when doing coastal hopping (oops). And that is where my iPad comes in handy. Because I take my iPad back home it is easy to make sure that I have the latest updated chart version on it whenever I come aboard.

Being a computer professional and a Unix/Mac user for a long time, I can only confirm the importance of all the points raised by you.

A last remark with respect to point #5 Battery Powered. I tend to use the iPad only in the wheelhouse. I noticed that in order to use my charting program the iPad must be connected to the ship’s power and even then it only just can keep up with the power drain caused by iOS and the charting program combined.


Dag W

Hello John

In addition to all these important remarks, I would like to highlight one particular risk. On the iPad (with built-in GPS) and with different kinds of navigation software, it has happened to me that the position no longer updates on the screen. It’s not an obvious freeze of the software, what you see is simply your boat in an old position, without any other visible indication of anything being wrong. So always look long enough to ensure that the screen actually updates as the boat moves.

Obviously similar things could happen on any system, but I believe different hardware/software combinations on tablets increase the risk.

Dag W

Rob Gill

Hi John,
Another great topic. We are using paper charts for route planning and situational awareness, transferring waypoints and legs into our Raymarine MFD at the nav station, which uses vector charting from Navionics. We then have an iPad with Raster charts from iSailor that we use in a Lifeproof case. This fits into a robust tablet holder nestled into the star port of the coachroof halyard winch. The iPad also acts a repeater for all the Raymarine MFD screens and functions. One of my favourite uses is displaying “DATA”, showing favourite instrument screens with course, speed, wind, compass, engine gauges etc. All of this from our preferred poor weather lookout position under the protection of our canvas dodger, but where we don’t have space for a full MFD. When we need the winch (infrequently), the iPAD pops into a pocket in the dodger. We will need to take care to cancel the pop ups though – great point.

Since we also don’t have a full paper chart folio for the Pacific (just passage charts and island groups). Detailed paper charts are so expensive for the Pacific in NZ. We mainly need British admiralty charts and these are $85 NZ each – ouch! But we like having the safety and redundancy of the three different chart types. We also like that piloting using electronic vector and raster charts simultaneously will minimise the opportunity to miss chart detail, and provides a check for important detail that may be missing in our electronic or larger scale paper charts (we were told yesterday that a latest whiz bang Garmin MFD with the top-of-the-line C-Map level charts doesn’t show the Minerva Reefs on the way from NZ to Tonga, at any scale! For us, this would be like a Euro chart not showing Ushant.
Lastly John, I’m not sure we should be so quick to dismiss the mobile phone as a back-up navigation device and the grab bag (we also have a passive reserve charger that can charge the iPhone, Sat phone or VHF). I have Navionics on my iPhone – I think it cost me just $64 NZ for lifetime Australia, NZ and Pacific charts in a special offer in iTunes AppStore. I do believe this could be safely used IN CONJUNCTION WITH OUR PAPER CHART, routes and pilot books, should we lose both the MFD and iPAD. We nearly always take this iPhone with us in the dinghy in a waterproof snap-lock bag as a form of emergency comms (assuming we have cellular coverage), as emergency GPS positioning device for SAR and emergency light. I can use all the functions of the device including talking, without taking it from its 10c plastic sandwich bag cover. In suspect mobile coverage and/or weather we also take our waterproof handheld VHF.
best regards,

Rob Gill

Sorry, “read smaller scale paper charts”.

Rob Gill

Hi John,
With just the Raymarine application acting as a duplicate MFD running across wifi, battery consumption hasn’t ever been an issue to concern us. We have only had iSailor for this NZ summer season ahead of going offshore for the winter, so we haven’t needed both running in parallel for extended periods. Offshore we will not run both iSailor and Raymarine/Navionics all the time but swap between on the iPad, exiting the app if we need to conserve power, so I don’t expect this will be an issue either.
But, having read your article and the comments, we will load Jenny’s iPad with both apps also, so we bring our own device on watch fully charged in their sealed case.
With regard to waterproofing, our dodger area is quite dry and protected except in really rough conditions, but I am not planning to run the unit outside with a 12V charger installed – I have heard from several sources that using a case will heat the device, drawing in moist salt air through the charge port, causing corrosion and eventual device failure, although I haven’t had this problem personally. I feel we are no worse off than having paper charts in their clear bag on top of the companionway hatch cover using a chinagraph pencil – this is how I grew up navigating in open day sailers and small keelers as a youth, and still do today when we want the immediate cross-check from helm to navigator.

Rob Gill

Hi John, just back from a short coastal cruise. As a test I ran my iPad with both apps on the return passage of five hours. From fully charged, we used around 15% of the iPad battery for the first two hours. We then experimented with simulating night time operation by turning the brightness down to the lowest level, drain reduced to around 8% per hour. I still have 46% battery life this morning.
Checking under “Battery” in settings over the 24 hour period, the Raymarine control app used 69% of my power, iSailor 26%, Safari 2%, Settings 2% and home/lock screen 1%. Since the Ray control data screen showing the instruments was our default, this reflected our usage well (note Safari use would have been since getting home on wifi).
Note: to simulate being offshore, I turned off unusable functionality like mobile data and bluetooth and closed other background apps. Wifi was running to connect to Raycontrol.

Serge Paul

The iPad will often overheat when in direct sunlight.
My primary Navigation software is a MFD from Navionic wich I love, but I always have the following backup ready PC (Fugawi and OpenCPN) and IPad both with there own and independent GPS all of them contain the waypoints of all the places discussed in my favorite Nautical guide(s) and all the routes that I have plan, which will change (they always do) plus I always have the paper charts for the next leg readily available. The PC is used for all my planning because I find it much easier. The IPad will easily shut down because of overheat, so to me the overprice MFD is still the better solution.
That being said, if sailing offshore (more than a dozen miles or so with no danger to navigation (on charts or nautical guide) I usualy turn off my MFD and rely on my paper charts with a GPS waypoint posted every 4 hours or so.

Marvin Hamm

And for exactly these reasons, I don’t understand why there doesn’t exist an 10″ ePaper screened handheld GPS device. Imagine being able to see the screen in bright daylight with your sunglasses on and getting days of battery life out of it.

“…real navigators never, ever go anywhere without laying down a course” – I get the point, but don’t have the experience to understand it. I sail on Lake Winnipeg, nothing on oceans yet. So I have a very limited perspective/experience. But what are the factors the necessitate the need to lay down a course before leaving? Anything beyond tides, currents, traffic, being swept out to sea? What is a journey small enough that in reality, you actually don’t bother with working out a course? (If you’re willing to admit that you didn’t. ) To what extent does this not apply when you are sailing in your regular stomping grounds vs exploring somewhere unknown?

Marvin Hamm

And, what is the refresh rate of a paper chart? I was presuming that would be the complaint against ePaper, but really, if your map only updated every 30 seconds, how bad would that be? Even every minute or two wouldn’t be that intolerable. I’m not talking speed/depth/wind. I’m presuming the boat has a proper set of instruments to give you that data in real time. And having this delay in maping might force us to think about charts a little more like I think you’re suggesting – A guideline to help us deal with the real world around us at the moment.
The more instant and the better the chart data, and the more accurate our location on that map, the more we presume that the chart ‘is’ truth, when the only truth is that which our boat is floating in/towards at the moment. I can’t imagine any scenario where having your GPS data 30 seconds out of date would create any problem for a sailor properly watching where they were going.

Jim Evans

Hi Marvin,

One factor that DEFINITELY requires a course before leaving is being singlehanded. If I’m on a voyage of more than a few hours I’ll have a Plan B ( and sometimes C and D) plotted as well.

I use a laptop with Nobeltec down below, hooked up to a handheld GPS in the hatchway.
I can upload routes to the GPS and use the track shown to correct my steered course and show cross-track error. In addition I now have a new iPad running Navionics on a mount under the spray hood (for spray and sun shielding) or on the binnacle for close- quarters manoeuvring.

The laptop is definitely the best for route planning (who wants to sit outside at a chart plotter in the rain when you don’t have to?) but I would rather have a chart plotter at the helm than the iPad. I just couldn’t afford one I liked. I’m looking forward to seeing how well the iPad works. The Navionics software is certainly quick and easy to use: a bonus for singlehanding.


Great article and comments, John. I suggest you develop a poll among your readers to list and rate all of the various navigation apps. Some are great and many are worthless. Many of the anchor dragging apps for example are useless, hence dangerous to operate. Help us separate the wheat from the chaff!

I use my iPad extensively for navigating on US East Coast using Navionics with Active Captain. But it’s no substitute for paper charts as some have noted. The iPad does not provide any of the very important navigation notes. I always cross check the iPad with the paper chart when planning a transit.
Once when transiting from Provincetown MA to Gloucester, MA, we accidentally ran directly through the prohibited LNG port area, having forgotten to check the paper charts. We were summarily re-directed by the guard ship. Lesson learned. SV TomTom, returning to 16.

Jim Evans

Hi John,

I’m not sure this applies to Canadian charts on Navionics. I haven’t found anything missing here in the Gulf (although maybe I just didn’t find it was missing…)

Dave McDonald

Hi folks – my first post here so be gentle 😉

As an astronomer, night-vision is very important for visual observers. The general rule of thumb is you need about 30 minutes of darkness before you become fully dark-adapted. Any exposure to significant light, and your eyes have to re-adapt from square one. Note – moonlight (half full, waxing, waning) is bright enough to illuminate the land/sea/objects so dark adaptation is moot.
As a (very novice) sailor without electronic navigation and sticking to charts (though I’ve used the iPhone once for coastal hopping on a 25nm round trip), I can only offer you my experience as an astronomer.
For any screen-based work at the telescope, (star) charting software would have an in-built “red-light” mode. Some would allow a timer whereby it would switch automatically to night-vision mode at a predetermined time (say half an hour before astronomical twilight).
If anyone is searching for such an app, try using the word “astronomy” and you’ll probably find something. And astronomers are notoriously stingy so most will be free. They are also very tech savvy and undoubtedly one of them has written such an app and handed it out for free. I often found it took my brain a few minutes to adapt to this “red” mode – so I’d recommend practice first – you don’t want to be learning to see what you need to see in the middle of a situation.
The one piece of software I *have* used and can attest to is f.lux. It doesn’t do night vision though but it tracks time and based on you input location, will “warm” the display screen when twilight hits. Its easy on the eyes – nothing worse than switching on a display, say in the cabin in the wee small hours, to be greeted with a retina searing white screen. F.Lux does support iThings and is also free. It may not have much use for night-time navigation (except maybe in the evening times) – the night-vision app is probably what is needed for that. But for anyone doing a bit of work in the evenings on a PC/laptop in the cabin, it can take the edge off the screen brightness/colour temperature to the extent that it certainly reduced fatigue in my case. Perhaps writing articles etc… But don’t do any colour dependant graphic work in “warm” mode (there is an override option for that though).

And no, I wouldn’t have clue how to navigate by the stars. Yet.

Andy Schell

I second f.lux! Though it’s now built-in on iPads and iPhone in the latest software update and is called ‘NightShift’. It’s a simple setting and makes nighttime reading much easier.


I use OpenCPN on a Sony Z1 — 5″ screen phone. Agree that 5″ isn’t ideal, but being 1920×1080 it’s not too bad (if your eyesight is up to it!). We don’t sail in any difficult areas for navigation (yet), so it does the job for now anyway.

I do recommend considering the Sony range of phones/tablets for those in the market — primarily as they are waterproof (have been for years), including while charging. They are also very robust — aluminium chassis seems to protect the screen very well, mine has suffered many serious drops over the years with only minor cosmetic damage. Battery life also seems better than the Apple/Samsung alternatives.

Andy Schell

John, you beat me to it! This has been on my mind to write about for a while, and perhaps a more fleshed out follow-up on exactly how we navigate with our iPad will be forthcoming. But here’s a few summary points to start. I’d like to say I use paper-only, if for nothing else than that it’s fun and challenging staying ‘old-school,’ but the reality is that the iPad is so good, and so convenient, that it’s evolved into our primary means of navigating. We do not carry a built-in chartplotter, though do have radar.

Our process (mainly for long, open-water passages, though this same process applies for the larger scale navigating into and out of our landfall harbors):

1. We layout the passage plan on paper, marking off waypoints at specific turning points on the course, and plotting the true course and distance in pencil on the chart. Old-school.

2. We make a notes sheet that hangs at the chart table with each ‘leg’ of the passage, noting the distance, true course, course to steer (TVMDC), and prominent landmarks or challenges (tides), etc. This note sheet is printed, by hand, twice – once to post at the chart table, and one to stick in my pocket to take to the helm (note: we have no instruments outside save for wind, speed & depth and a fantastic C. Plath Venus binnacle steering compass).

3. We transfer the waypoint coordinates from the paper chart onto the iPad running Navionics charts on iNavX, the pull those together into a ‘route,’ checking our accuracy from the paper charts. Importantly, we DO NOT ‘START’ THE ROUTE IN THE NAV SOFTWARE. We set the iNavX to ONLY display waypoints from the currently selected route to remove undue clutter.

4. iNavX overlays AIS data and pulls position data from our Vesper XB8000 ‘black-box’ AIS transceiver over a wifi signal (which, knock on wood, has never failed us). The iPad gets charged the night before departure (we have a checklist for this, which includes a whole host of other pre-departure items), and it remains in the cockpit until Isbjorn is clear out to sea and into open water. Battery drain is nominal and we keep it out of the sun. The helmsman is NEVER the navigator, even if it’s just Mia & I.

5. By NOT starting the electronic route, we can easily adjust underway without the distraction of the unit beeping at us and showing cross-track error all the time – the iNavX software displays a blue dotted line as our route, and we can see easily where we are in relation to that at a glance, in real-time. We set a range-circle around the position icon based on the conditions – smaller for inshore navigating, wider for offshore – and a timed COG vector that shows our future position at the current SOG in 30 minutes.

6. Once offshore, we simply plot on paper at our noon position (logging the coordinates every watch change or 3 hours, but only actually plotting on paper once per day). iNavX continues running in the background at the chart table while plugged in, and crew check it regularly for AIS targets during their watch routine. Helmsman is free of all distractions and instead gets to gaze at the stars she’s steering the boat by!

At all times with this method we have that initial cheat sheet posted at the nav. table – we could literally navigate the entire route using only that and the ship’s compass – it’s like a mini, customized pilot chart for where we’re operating and is a great, simple backup tool.


Marc Dacey

Interesting how you differ and are the same on these points. I like XTE info for the same reason I like setting the AP on a vector, not to a waypoint, because the lee made contains clues about currents, sail set and other things I would prefer to know.

I think we are all agreed that the helm should handle the helm and not the nav, and I like the idea of a “start chart” with WPs listed and, presumably, checked off. Estimates versus reality also supply (to my mind) further data points. Imagine you are making 20 NM/day less to your next WP than you think you should be based on your history on that point of sail. My first thought would be in the first calm patch to dive on the hull and see if I was dragging something!

Andy Schell

My main reason for not selecting the route on long passages is more to do with the way the data is displayed – oftentimes you end up seeing ‘Distance to Waypoint’ and ‘Time to Waypoint’ items which, when the waypoint might be thousands of miles away, are very distracting! You end up playing this ‘when are we going to be there’ game which totally removes you from the ‘moment’ and enjoying the time offshore.

This wouldn’t apply inshore as much, though it’s still a factor. I’m guessing there is a way to tweak these data displays but I just haven’t messed with it that much. I’m happy with our simple setup – the overall point being to find something that works for you, and keep your eyes open for being with better ideas!

One thing not mentioned in the post was cost-benefit – an iPad running good software and being used responsibly offers huge bang for your buck.

Tim Gift

I use an ipad almost exclusively to travel along the west coast and up into Canada. I do have paper backup, but rarely use it. I have two ipad backups (family members), and two iphones also with navigation software. Lot’s of good points brought up, but any system will have it’s good a bad… anyway, I just wanted to add that touch screens don’t work well when they are wet, as in the rain. Very annoying 🙂


A few thoughts…. Good article !
Straight away having no backup is too scarey for me! 😉

I use a raspberry pi down below with a sony xperia under the sprayhood which works just great.

BIG benifit of the more diy mini computers is how easy it is to connect other sensors – I have graphs of engine, exhaust & alternator temperature real time which is a wonderful early alert to any engine temp issues on the way. Battery voltage soon as well.

Can opencpn run in an ipad? VNC is too clunky with the Pi so I run it as an app on the xperia- another big benefit further afield is being able to have google earth images as charts. Also, with opencpn it’s easy to do the planning down below on a decent monitor (or laptop) then copy the navobj.xml files across so each device has the same routes etc.

Wifi – never had a problem so far but have had nmea wires come adrift in the past – is wifi that unreliable?

Also for any kind of complex passage isn’t a written passage plan fairly essential? All goes down, follow the compass 🙂

Richard Hudson

Hi PaddyB,

Though I’m going off the topic of tablet navigation, I was interested in your description of a Raspberry Pi as an engine monitoring system and had a couple of questions.

How many temperature sensors can you put on one Raspberry Pi, and what do the sensors cost?

For the exhaust gas temperature sensing, where have you mounted the sensor to get the (not cooled yet) exhaust gas temperature?



Sort of slightly on topic as it gets viewed mostly on a xperia tablet in the cockpit 🙂

The thermometers are dead cheap, ds1820.
Not sure what the limit would be connected to a pi, probably more than you would ever need on a boat. They all have their own software address and can be daisy chained together so only one data wire goes into the Pi. The openplotter software then makes it easy to set up. The latest experimental openplotter V0.9 is heavily into signalK so the numbers get sent out as signalK. At the moment I have one epoxied onto the alternator, one cable tied onto a lifting lug on the cylinder head and cable tied onto the exhaust bend so measuring after the water injection.
Works great, having a graph gives early warning , I had a water input pipe blocked with pine needles a little while ago which was spotted as the temp gradually went up.
All for 0.3A which the little Pi takes. 🙂

Richard Hudson

Hi PaddyB,

Thanks, that looks like an excellent setup you have for engine monitoring.

For those following this sub-thread and not familiar with the Raspberry Pi, it is a low power consumption, inexpensive computer, running Linux, typically sold without a display. Technically-inclined people use them for all sorts of purposes, including navigation.


Marvin Hamm

Can you give us a link to the software/apps/code you used to build that kind of screen? That looks so useful. Love the graph.


Marvin – That graphic might be part of the OpenPlotter package:

Their documentation is a work in progress, however there is already a lot of information in it, including basic sensor setup.

They have links back to some of the packages they use (e.g. Signal-K). When Paddy gets back online he can tell you if that graphic is part of the package or if he wrote it himself.

If you are looking specifically for some graphics packages, one of the Signal-K developers is toying around with SteelSeries Gauges. He made a pretty cool wind sensor graphic a couple days ago. Here are some of the graphic capabilities:

It’s all open source. That’s the beauty of these projects….customize till your happy. But if you will use it in a critical system, then test it for a year in real conditions so you don’t incur John’s wrath 😉

Good luck and have fun with it!


Hi Marvin, the main software is openplotter as RobertB pointed out. The gauges I wrote in a graphical program included in the pi operating system called node-red. It reads signalK data and displays it, not too hard to set up. But as soon as the sensors are plugged in you can see the data elsewhere, just not as pretty 🙂
And John, I think you’re being a bit hard on it, openplotter must be about as good as it gets for a boat nav system and is very much working straight out of the box. Load the software onto a SD card then set up the nmea sources and off it goes sending NMEA and signalK over wifi. Mine has been absolutely rock solid at sea so far for must be well over a year, though I’ve managed to crash it now and again experimenting. For the price of decent meal and a few hundred milliamps it is well worth considering as an add on even if not a major part of your nav system, definitely not just for those with slightly geeky tendencies 😉


PS – Meant “software for a computer nav system” above.


I absolutely agree with you regarding DIY (the new “home brewed”) systems vs commercial systems, with some commentary though. It is caveat emptor and if you are not willing to put a substantial (albeit fun) amount of time into learning, then go with a purpose built system.

Re hardware – Computers like the Raspberry Pi (< $40) are designed for the educational and hobbyist market….not commercial use. Granted they have done an excellent job, which is why they are insanely popular for almost any application; however I would caution against using them in a critical system. The choice of components is not commercially driven and they are not hard to blow up. A more industrial version can be 5-10x that cost. This is the same reason I wouldn't choose a $60 tablet for offshore.

Re software – That's a little different. Some of the open source software out there is pretty robust. Considering the state of commercial marine software, which has been complained about here, my feeling is that it comes down to how long the software has been out there and how many people are using it….regardless of whether it is commercial or open source. You will find that critical bugs will generally get fixed much faster with open source than with commercial systems. Many open source boat software developers are both boaters and professional software developers that were sick of what was out there labeled "commercial." They are every bit as talented and probably more motivated to make a robust product. I put a lot of the Signal-K and OpenCPN developers in this group. Caution is still advised though. As with any other piece of equipment or software, you need to put the time into understanding it and testing it under your intended conditions.

That said, if you are going to use the open source and free software, you should contribute back in some way….donate, write about it, test it (and give feedback!), etc. Just get involved in the community. There is absolutely no need to be a programmer if you don't want to. There are never enough people testing and reporting back on issues….or writing documentation. One plug for these people…they are very gratifying to work with. Try that with the commercial systems! 🙂


Chris Carlin

I think I’m a bit confused or misunderstanding comment #3 wrt. the accuracy of internal vs. external GPS HW. My ipad, iphone and android phones/tablets have internal HW that includes support for both GPS and GLONASS satellites (the combined usage by the device improves overall accuracy), and depending on the unit/situation they regularly report to be within +/- 2-4 meters accuracy. So, even though WAAS correction should technically get one within 1 meter of accuracy even the Bad Elf GPS external unit you referenced that has WAAS (but not GLONASS) states it only has +/- 2.2m accuracy. So, if one recognizes the limitations of *any* GPS system (including compensating for where the receiver is at the moment, etc.) are the differences between internal and external HW really meaningful? Thanks.

Jim Evans

Hi Chris,
Agreed. And given the fact that many charts are way less accurate than that – it doesn’t seem important. Back to lead, log and compass!

Bill Attwood

Hi Richard.
A measured and logical response to my semi-rant. Thank you!
I agree that there are one or two places where offshore weather info can prevent an unpleasant experience, the Gulf Stream (which I haven´t experienced) and the Agulhas Current (which I have), perhaps there are others?
I also have Radar and AIS, and wouldn´t be without them, but consider them as aids to navigation rather than basic navigation tools. I haven´t sailed in fog-prone areas (I don´t think the English Channel really qualifies). Compass, trailing log, charts, sextant and tables are my tools, with a basic GPS to improve the accuracy of my sights and DR. I should also add that I have a large collection of pilot books which can help in the event of an unplanned diversion.
I don´t sail single-handed any more, so my wife is always on hand when wed are engaged in coasting/pilotage. Like Andy, we use written notes on a whiteboard for pilotage, or for longer trips eg cross channel Plymouth to St. Malo. Offshore we write up the log every hour, and mark our daily position on the chart as at midday each day.
It just seems that every post about electronic navigation seems to generate a flood of comments about all the problems which can arise, or which have arisen. Rare is the comment which says how perfectly everything works. I can see the benefits of a totally reliable electronic system of charting, but even SOLAS insists that commercial ships not having ECDIS must carry a full set of corrected paper charts. And I believe that these systems cost in the hundreds of thousands.
There may come a time when recreational systems are reliable enough that I shall use them for coastal sailing/pilotage. But I may no longer be alive when that time comes.
Yours aye,


While I can’t comment on real ocean navigation I’d point out that Android based tablets are an option rather than Apple.
I use Navionics on a couple of Android tablets – battery use is demanding – but plugged in they stay charged. I’ve not had long enough or demanding enough trips to overheat or challenge things too much – but so far so good (even with rather old tablets).

A few Android thoughts – I’ve yet to come across an Android tablet that didn’t have built in GPS (where as Apple only builds in GPS if they are making the device cellular capable).

The cost for Android tablets can be dramatically less – actually less than what you’d pay for a waterproof case for your ipad — at Costco you can grab a 7″ Acer tablet for $100CDN (must be $60US!!!) – with GPS. Smaller than you want for a primary – but quite adequate – add a zip lock bag and your off. Processors can be slow – but I’ve found them good if I clear other background apps. Bigger screens and faster processors are avail

With a single Google account you can load the same navigation software onto all for one fee.

I have yet to learn paper chart navigation – it’s on my list of things to do…


Serge Paul

You have yet to learn paper chart navigation – it’s on your list of things to do…

I will certainly not say what is going thru my mind, but please make it a priority.



My sailing to date has been 98% day sailing in familiar protected waters, with recognizable landmarks, and the other 2% has been short coastal hops to move the boat to and from winter storage – again never out of site of land and with easy line of sight navigation.
I don’t think my paper chart skill need to be a priority. But it’s something I want to learn so I can start reaching further out.
Maybe I’m wrong


Mark – I agree. I think Android devices are great for navigation. You will see a lot of iPad people because decent navigation apps came out a lot faster than with Android. It’s only recently that I have considered the software good enough to switch.

However…I would strongly advise against using inexpensive tablets for navigation. I run an engineering company and have spent the past 2 years developing accessory device sleeves for tablets. My customer insisted on using these inexpensive tablets and I have found they are very hit or miss. I cringe every time the next inexpensive device comes out. For something as critical as navigation, I would stick with good hardware. That’s why many choose Apple…the hardware is usually very top notch and they control both software and hardware. There is no reason not to use the quality equivalent in Android (e.g. Samsung, Nexus, etc), but they tend to get just as pricey as Apple. Personally, there is no chance I would use a $60USD Costco special for a critical device.

My suggestion to people is to stick with the OS that they know. The last place you want to be futzing around with your device & apps (like killing a background app that somehow started and is causing you problems) is on a rocking boat in a critical situation.


Richard Hudson

Hi Bill,

> It just seems that every post about electronic navigation seems to generate a flood of comments about all the problems which can arise, or which have arisen. Rare is the comment which says how perfectly everything works.

Yes, I see your point. There are problems with electronic navigation systems. The better the implementation, the more reliable it is, but it’s still essential to have a simple and really robust backup method (like paper charts).

You bring up a good point about regularly filling out a (paper) logbook. Much as I like using electronic navigation, my paper logbook is filled out regularly, so no matter what happens, I still have a relatively recent position written down, to start navigating from if necessary (and, a couple of times, that has been necessary 🙂 ).


Marc Dacey

The paper log is not only a huge aid to situational awareness, as the act of writing down an hourly record of weather conditions and positions, VMG, etc. is not only the guarantor of coming on deck with one’s pants half up and not wasting time asking a bunch of stupid questions, but is also still a legal requirement for surprisingly modest commercial vessels and may be of interest to one’s insurance broker, should it come to that. I have binders of incident-free logs of trivial sails, because I wanted to encourage the habit.

Jim Evans

Having suffered a bout of total amnesia at sea – singlehanded – I can testify to the value of a paper log. I don’t always keep one on a short trip ( less than 24 hours) but I should.
I strongly second Mark’s comments.

richard stanard

a lot of tech jargon in all this…i venture to say that most of us readers including myself have eyes that glaze over when confronted with tech jargon including use of initials only such as waas or ais or chirp although i guess most understand vhf and gps…i think those who recognize tech jargon and initials are in the minority…sort of defeats the purpose of posts like this…also, my understanding is that mobile devices are useless once out of signal range…one doesn’t need to venture far at all offshore before this happens so why would this be a viable option for anybody who even occasionally voyages offshore? what am i missing here?

richard s
s/v lakota

Andy Schell

Hi Richard,
Fair point on the abbreviations – might be worthwhile for AAC to include an index of all that, easily referenced to avoid confusion?

As to the connectivity, it’s not an issue – we sail Isbjorn offshore all the time, 10,000 miles per year, and an iPad is our primary nav tool – here’s why:

1. You’ve got to download the app and the required charts while on wifi or cellular data – we use iNavX, and purchase Navionics charts that we download and load into the program – all of this data is saved locally on the iPad ONCE DOWNLOADED. This requires some forethought and planning so as to ensure you’ve got the right charts onboard!

2. Most iPad’s have internal GPS receivers, but as John said, they aren’t as accurate or reliable as what you’d need to navigate. So we, and most offshore sailors running iPad nav tools, use an outside source. In our case it’s a Vesper XB8000 AIS unit that has it’s own dedicated GPS antenna, mounted on the stern rail and wired to the Vesper unit, which resides out of site behind the nav. station. There are lots of these out there, the simplest being the Bad Elf external GPS. Lots of pilots use this as well for the same reason.

3. The Vesper unit (or whatever your external GPS source is) than streams the GPS data (along with AIS data) from it’s own antenna over a wifi signal – we simply connect the iPad to this signal and have accurate, reliable GPS data. NOTE that just because we’re on wifi doesn’t mean we have Internet access – we don’t. The wifi is just the means by which the iPad communicates with the Vesper. Normal household wifi does essentially the same thing – it allows your computer to communicate to your router, which IS connected to the Internet, thereby giving your device a wireless connection.

So that’s how it works offshore – the iPad running internally saved charts, just as an onboard chartplotter might, and getting GPS position data over a wireless signal from an outside source. No Internet needed.


Bill Attwood

Just a short wise-ass comment which may be of use. Red light is of itself not the protector of night vision, but the reduced light intensity with a red filter. Dimmed white light is just as effective in preserving night vision.
Before any accusations of “alternative facts” are forthcoming, this info comes from my friend Noel, lifelong sailor and adventurer, and emeritus professor of anatomy and opthalmology!
I rest my case.

Bill Attwood

Hi John
Thanks for the link, interesting reading. I have forwarded it to Noel for his peer review.
One thing I found particularly interesting was the “eye patch” trick. When I was working in Berlin, and living on the (former) east side, the only time I could find to run was early morning, in the dark. I had to cross under the River Spree through a brightly lighted tunnel and then emerged into the forest. Totally black. Putting a hand over one eye as I traversed the tunnel solved the prob perfectly. Screwing the eyes up to reduce the aperture can also help. Since I don’t use electronic nav, I’m not familiar with the problems of too-bright screens, but I can imagine that it could be easy to inadvertently totally screw night vision. As a result of the long string of comments to this post I am even thinking of acquiring an i-thing but would appreciate it if you didn’t let that go any further.
Yours aye


dear John,
I couldn’t agree more to your comments. One remark from my side-probably cristal clear for you and your readers- but I had this discussion more than once in Europe: Only ipads with Mobile connection have a inbuilt GPS. The Wifi only ipads just replicate a look like GPS signal via Wifi networks around them if there around when you are on shore. To cross-check: there are also Apps around like “GPS Diagnostics” to check the connection and strengh of the GPS signal of your device.
best regards

Geir ove

we use ipad as backup, and as our papercharts. They are updated al the time. online. Old Papercharts dont get online update 🙂 so we dont have them onboard anymore, since 2011.
sailing from Madeira to Lanzerote in oct 2016, we got very bad W. and heavy seas. a lot of sea on deck on our Cat. and also into cocpit. wherte we have our speakers. thats when our normal chartplotter lost its GPS signal due to seaw inside our cabinet and came to stop our GPS, The mebran on the speakers was broken and let seaw into the cabinet. So Ipad out into cockpit middel of ninth as we got close to the coast and entering into Rubicon marina. I find the GPS on our iPad air very good. even our first Ipad from 2010 has a good gps.
There is even a lot more info to be found on the Navionics maps that you get on the ipad compaird to the info you can get up on our (now) old Raymarine E90W chartplotter.
And the big price diff ? chart plotter cost about 4 to 5 times the prise of a Ipad .
i will never leave home without it 🙂
easy to update, always latest charts. dont take much power. and the cost compaired to chartplotter and paper charts are BIG.
i love my iPad.
(sorry for my english as it is not my mother language.)

Erik Snel

I absolutely agree with your position that iPad and especially iPhone are not suitable as primary navigation instruments. The (possible) lack of stability due to interfering other apps or system functions is one reason, as well as the susceptibility to seawater.

What I do not agree with at all is the unsuitability as a route planning instrument. I find the PC programs very unsuited to planning trips, as it is quite hard to zoom in/out fast enough, which is very easily done on the iPad.
For route planning we usually have the following steps:
– use paper charts to get an overview of the intended rout
– plan this route in iSailor, and zoom in to every part of the rout (this is where the zooming of the iPad is very handy) to check any dangers and thus finetune the planned route
– transfer the route to the chartplotter to use while sailing

As our plotter is situated in the cockpit and is totally wheaterproof and stand alone (except for 12V juice) this setup and way of working is quite satisfactory for us, especially when sailing short handed or solo (which is quite often).

Francisco Moreno

We always run two iPads when sailing, and we always run three different chart apps, to check and compare. One of the apps must be raster-based, for that “paper chart” comfort level. Paper charts have no scan errors, unlike vector-based electronic charts.

Currently in the Adriatic, our setup is:
1. Vector: Navionics
2. Raster: MaxSea TimeZero (TZ)
3. Raster: Plan2Nav (C-MAP)

We like Navionics because of its fine-level detail, superior in the Europe to other alternatives, so it us our mainstay. Having said that, we have found at least 4 glaring errors: two ovh power cable clearances missing on the Guadalquivir below Seville, Spain; the missing bridge clearance at the Guadiana above Ayamonte, and bottom depths were utterly wrong in the approach to Tomás Mestre, near Cartagena, Spain. We reported the power and bridge errors and Navionics updated their charts in about 45 days.

MaxSea TZ uses only national hydrographic office charts, so if we are in France, we know we are using SHOM charts, in Canada we had peerless CHS charts, etc. No silly errors on these charts (!). Purchasing all the maximum-scale official charts we have used for a few dollars on MaxSea would have cost thousands on paper. When in doubt, MaxSea is our go-to solution and peace of mind.

C-MAP we bought only because our old mainstay Garmin Bluechart, which was so good in the U.S., is only so-so in Europe, so we gave up on Garmin for this side of the Atlantic. But C-MAP has been a disappointment due to buggyness of the app, and we only use it as cross-check for the others.

In the States, our setup was:

1. Vector: Garmin BlueChart (great also for the Bahamas)
2. Raster: iNavX
3. Vector: Insight Genesis (on the plotters)

In Canada, our setup was:

1. Raster: MaxSea TimeZero
2. Vector: Garmin BlueChart

Finally, we pre-load all the maps on both iPads, and whenever the app allows it (Garmin, iNavX, C-MAP), we also pre-load on the iPhones, so the iPhones could be used on emergencies. Always check that your map download works on all devices before leaving wi-fi range.


Francisco Moreno

Correction: Plan2Nav (C-MAP) is vector, of course. Many websites allow one to edit a comment, thus avoiding littering the thread with corrections.

richard stanard

i think i am in the majority here as one who has always struggled with high tech so i am not embarrased with this i-guess-basic question: will any or all of these programs or apps or whatever they are also work on my 4g tablet? or do i need to upgrade to the ipad to use these ? thanks

richatd s, s v lakota
tampa bay

Eivind Haugan

Hi all,
I’m currently preparing for a Europe to Caribbean crossing, and plan to upgrade my regular iPad to an iPad Pro with a 12.9 inch screen to get a better resolution and detail.
Have anyone experience with these and if we can expect any compatibility problems with Navionics charts and B&G GoFree application or other navigation apps?
Please note that the iPad Pro is just meant to be a back-up for two B&G Zeus MFD’s and also used as mirror of these screens.
Thanks in advance
Eivind / Abraxas 3 / NOR-12050

Eivind Haugan

Hi John,
Still winter and ice around here in Oslo so no sailing until late April. Will report back. Found a waterproof case from Catalyst that looked good.
Haven’t bought anything yet as there are rumours of a launch of new iPad models scheduled in March. If so we might even get a basic waterproof iPad in line with the iPhone 7. They will of course need more protection, but it doesn’t hurt if the contents within the cover is waterproof itself.

Charles L Starke

I also wanted to get the larger iPad. At present, I use the 9″ one with waterproof Pelican case as a back up with iSailor running. It is easily fed GPS (by GPS puck) and AIS (from a Vesper unit) info by Bluetooth and wifi. It works really well with a ram mount at the wheel, under the doghouse, at the Nav table or above my bunk (for navigation or movies).
The only waterproof case for the 12″ Ipad I could find on Amazon was
Unfortunately it is $159.90. I’d love to have someone’s experience with this before I plunk down my money!

Robin Bower

Since my sailing budget is restricted I set about to look for cheap and reliable substitute for a chart plotter while sailing on the Great Lakes. For the past 2 years I have used an IPad 2, loaded with a Navionics App, coupled with a Bluetooth connection to a Bad Elf GPS receiver. At $199.0, the Bad Elf is a great buy, (I bought 2 of them). I can locate the receiver in the best position for sattelite reception, (it is water resistant) and keep my iPad in a warm and dry location. Satellite capture occurs in less than 10 seconds and accuracy is usually within10 feet. The Bad Elf supports up to 6 devices at a time so crew members can use their own iPhones or iPads for navigation if they desire. Gives me great back up for my aging iPad. FYI, I also carry paper charts.
The folks at Bad Elf provide excellent online support

Larry Giordano

Great article but I have a question. What tablet has satellite derived GPS? All I have found is Cell tower positioning so if you’re off shore out of range??? I know that we can purchase Blue tooth/wifi devices to pipe it in but this article makes no distinction. What am I missing?

Martin Loxton

All cellular iPads have satellite derived gps.

Larry Giordano

Don’t think so, right off of google: “The GPS system in iPads and iPhones relies upon the cellular connection. It uses the towers to pinpoint the location. If you get a non-cellular model of the iPad Air, then you can only get location from wifi.Nov 1, 2013”
So unless something’s changed since 2013… On hold with an APPLE store right now but it’s xmas time…