Seen various people say to never use a phone/tablet for navigation. Why?

[boat driver]

Your application lacks a couple details-
Power source? GPS source?
The rest is elementary to your preference.

1) The GPS on all devices is a power hog. So be aware the models utilizing various the runarounds on the phones and tablets as are they true gps units- vs the hybrid utilizing terrestrial tower units-
2) To reduce the power use, the phones and tablets use one line of position (basically one satellite at a time) and advance this line. So accuracy is unknown particularly at faster speeds. ) gross example is vehicle overrunning road when operating in interstate cloverleaf)
3) Below decks and under sail obtaining good satellite sight is often dubious, again particularly in fog and sail damp applications. GPS is a weak powered signal so easily interfered with by atmospherics/objects/electronic noise/

If the power is external and the GPS feed is a "minimum" three satellite LOP (line of position) then no reason to use whatever (display) you choose.

The issue is understanding the limitations of the equipment chosen, as well having backup plan B when the primary system fails, due to electrical loss, lightening hit, power surge, water intrusion, etc.
Therefore, having multiple fully charged phones and ipads with navigation basic programs is ideal.

[wingssail]

Originally Posted by cabosn

...A little background. The GPS performs two distinct functions. The prime function is to receive the navigation signal and determine position based upon timing. A second essential function is to download the almanac. The almanac contains all the information necessary about the position and frequency of the satellites. I don’t know how often it needs to be updated but it’s quite often. It depends upon how far the satellites have moved and how far the GPS has moved. Depending upon the current software, the GPS will eventually stop giving you position data when it has determined that it’s almanac is too far out of date.

The iOS GPS is unique because they decided not to have the data download capability from the satellite. Instead, they chose to download the almanac data from the Internet. no Internet, no almanac. Something that was unknown to us early on was the fact that almanac data could be downloaded via cell service even without a subscription. This meant that if you had an iPad with no Wi-Fi connection and no subscription your GPS would still work as long as you were in cell phone range (or Wi-Fi) when you needed the almanac. It is still unknown to me if this free download capability is available everywhere in the world. I know it is available in many places in the world but that might not be good enough...

That is so interesting! Thank You.

OOps! I just read that this is inaccurate (but still interesting)

[Auspicious]

Originally Posted by Duxa

Settings -> Accessibility, then toggle ON Zoom (it will zoom in), double tap 3 fingers to return to normal zoom (or use slider on the bottom). Then tap Filters and select "Low Light". Then use your normal brightness slider to slide all the way down. If its day time the screen should get so dark that you wont be able to tell its on.

<snip>

On the brightness side, iOS devices have been 600nits brightness typically. Great news is that devices they just announced last week (next gen of apple devices) are going to be 1000 nit brightness, which to my understanding is the brightness of the on boat chart plotters.

The Accessibility > Low light does make it dimmer. Still not great.

Apple has been promising "brighter" for generations (of phones, not people) and haven't delivered. I'll believe it when I see it.

Originally Posted by RnJBSailing

first time out & back on Great Lakes with polarized sunglasses (prescription) and none of us could see/read the darn thing in the sun!

I gave up on polarized sunglasses a couple of pairs ago. Just too many things with LCD displays at odd angles.

Originally Posted by Duxa

There is a post on Apple forums that seems to indicate that at least since iOS9 you can get GPS without cell towers anywhere and with no almanac already on the device.

iOS 9 is about when Apple stopped turning off GPS in airplane mode. Nothing to do with ephimerides.

Originally Posted by Duxa

It also shows that almanac is broadcast every 12.5 minutes. Which explains why it can take such a long time to get a GPS fix, if you start looking right after it just broadcast your device will be just waiting for 12+ minutes. Then it will take another 12 minutes to actually receive it.

They got the periodicity correct. The actual broadcast length isn't nearly that long. I don't remember off the top of my head. It is analogous to static and dynamic data in AIS.

Originally Posted by Duxa

I think the most important piece of information though is that Almanac is NOT required for GPS to work.

Not quite. You need the ephimerides. They come with the broadcast data. The calculation goes faster with a good seed. That's all. The device has to know where the satellites are for the time delay calculations to work.

Originally Posted by Duxa

Note, as of iPhone 11 (2019), with cell/wifi off the GPS is showing to be about 10 meter accuracy. Note the circle around where it thinks I am. 5 meter radius.

You should get much better than 10m accuracy with a good view of the sky.

Originally Posted by Duxa

Phones can augment GPS with AGPS and cell tower triangulation to get better fix.

Not better. Faster initial. No better performance after that.

[CaptnKen]

TMI... simple question ... simple answers. WOW why I don't usually get involved in most posts. KISS is my moto.

[Mr Fox]

I think most of the issues with a tablet are answered by getting a non apple product. Samsung galaxy tab active pro is a good choice. Built in GPS (not cellular based) IP68 rated (yes even the plugs, even when charging); direct sun is not as good as a plotter, but not the end of the world with a polarized anti glare film (mine sits under the dodger so no problem). Touchscreen works when wet and with gloves.

Stays plugged/fully charged at all times, and if I lose power I've still got about 8 hours of navigation (a few days if I don't use continuously, also you can swap its battery with a fully charged one in under a minute, try that with a plotter). Pops out of its model specific ram mount in less than one second and goes below when leaving the boat. Ram mount is hard wired so it charges whenever its clicked in (and is still IP68 rated). It's less than 600 to your door for the 10 inch, around 300 for the 8.

It also has higher operating temperature than an iPad. If it is getting too hot it can shut down it’s charging and run off the battery to cool itself.

I update the navionics charts and tide info whenever in range of wifi (or cellular as it can connect via a phone). Runs fine on the downloaded charts if I can’t (so does not ever require an update to navigate safely).

I find the current apps superior to chartplotters for my needs. Navionics lets me set a course on my phone and it syncs across all my devices running it (android or apple) full marina/anchorage/local info (uncharted rocks, number of the guy delivering ice in an anchorage etc.) Tides, current, wind and weather all available in the app. Bluetooth and wifi means it happily chats with my vesper and SH for full AIS integration/overlay and a redundant gps if need be. Can talk to other devices through the vesper for things like live sonar imaging of the bottom.

Bonus- you can watch a movie on it when bored

[wingssail]

We have an android tablet (rugged, waterproof, 1000NITS) which we take on deck and use for various purposes including piloting in close quarters, but its primary purpose is racing navigation and tactics, and it is proprietary software (SailRacer).

The real navigation occurs at the nav station using OpenCPN on a 15" windows laptop. The laptop has all ship's inputs and uses a mouse and keyboard.

Navigation there occurs in a clean, quiet, comfortable environment with a screen big enough to see detail. We can download courses and waypoints to the tablet if we want it on deck but the laptop with OpenCPN is the "Truth". We take care to have the best possible chart before going on a passage or a new area. We always plot our route ahead of time on the laptop (allways!). On the laptop we have access to dozens of routes and thousands of stored waypoints as well as notes, pilot charts, sailing directions, and guide books, all at our fingertips. In the nav station we have all the radios and all the displays of all the ship's electronic information. There is more to navigating then following a route on a tablet or phone.

Our nav station is close as you can get to a professional navigation station as possible.

For back up we have two other laptops ready to be swapped into the nav station. (of course we have a variety of phones and other tablets, but we don't use them). We have multiple GPS hard wired into the laptop. The power is ship's power, with the laptop batteries being backup. The screen is always readable inside the boat.

We've seen tablets fail and get broken or fail to display the nav app because of a persistent prompt to renew a subscription (which resulted in loss of a boat, not ours) of for other reason. We had a friend run onto a rock at 6 knots because he could not see the obstacle on the small tablet screen he was using.

But the real reason for our preference for nav station navigation instead of cockpit or helm station chart plotter is that I just don't want to be out there at the helm in shitty weather trying to run a touch screen or changing a course or waypoint while steering, etc. I get below and do it quickly and accurately at the dry, quiet, nav station with all the tools my laptop provides.

Have you ever seen photos or videos of a volvo 70 or a TP52 or a major ocean racer with an outside navigation system fastened to the helm? No and you never will. That solution, so ubiquitous on cruising yachts, is not suitable for us in most heavy weather situations when it is needed most.

[Mr Fox]

Just an FYI navionics will continue to function 100% if your subscription runs out, you just can’t update your charts until you renew. I find it beyond irresponsible that anyone would make a navigation app that would quit on you while potentially using it. Wow.

So many great ways for everyone to enjoy their boat in the way they like, as long as it’s safe, no wrong answer (except a sextant in my hands, because we’d end up in Norway while looking for Bucks Harbor).

[Auspicious]

Originally Posted by Mr Fox

I think most of the issues with a tablet are answered by getting a non apple product. Samsung galaxy tab active pro is a good choice. Built in GPS (not cellular based) IP68 rated (yes even the plugs, even when charging); direct sun is not as good as a plotter, but not the end of the world with a polarized anti glare film (mine sits under the dodger so no problem). Touchscreen works when wet and with gloves.

Apple and many other device manufacturers use chips like this one https://www.qualcomm.com/products/qu...9207-lte-modem that have both cell and GNSS/GPS on the same chip. The 9207 has WiFi and Bluetooth on the same chip. They don't have anything to do with each other. The higher level of integration reduces device size and power consumption. That's it. Some Apple products have FM broadcast reception in the chips just like many Android devices do - it isn't hooked up. GPS on phones and tablets is not cellular based. Apple has chosen not to implement GPS on their WiFi-only devices as a positioning (ha!) and marketing decision. Most Android device manufacturers have chosen to implement GPS in their WiFi-only devices. GPS Apple devices are no more cellular based than any other GPS. Period dot.

A-GPS (A-GNSS) is an enhancement, not a dilution of satellite positioning. See my post above.

Originally Posted by Mr Fox

It also has higher operating temperature than an iPad. If it is getting too hot it can shut down it’s charging and run off the battery to cool itself.

I didn't find any specs but I did find this https://www.samsung.com/sg/support/m...-during-usage/ which looks exactly like what an iPad does. I have seen customer's iPads shut down in direct sunlight. My own Android tablet (used only for entertainment) will shut down in direct sunlight.

Originally Posted by Mr Fox

Bonus- you can watch a movie on it when bored

True of all phones and tablets I can think of. My own old Raymarine E80 Classic has an RGB feed intended for an engine room camera but there is no reason you can't run video to it. See below for my current preferred solution.

Originally Posted by wingssail

The real navigation occurs at the nav station using OpenCPN on a 15" windows laptop. The laptop has all ship's inputs and uses a mouse and keyboard.

This is my preferred solution also. I use two screens (laptop and an ASUS M168b) on delivery, three on my boat (third screen is an HDMI feed to a TV on the forward bulkhead where I usually run radar), four at home on my desk. A picture is upthread.

I also use an Anker 10 port powered USB hub after having burned through a number of other alternatives. There are never enough ports on a laptop, and you can overload the ports there are with an unpowered hub. The Anker, like my laptop, can run directly off 12VDC. Plugged in include the outboard monitor, GPS, AIS, and charge my InReach, a flashlight, my phone, a cell modem, and a SanDisk Connect. The latter is by no means mission critical but a neat bit of kit. It's a thumb drive with built in WiFi. With 60 GB of movies on it, crew can stream any one they like from their bunks.

Nav on the laptop is "truth" regardless of what may be built into the boat or on a portable device.

Originally Posted by boat driver

2) To reduce the power use, the phones and tablets use one line of position (basically one satellite at a time) and advance this line. So accuracy is unknown particularly at faster speeds. ) gross example is vehicle overrunning road when operating in interstate cloverleaf)

Not true. First a position requires four satellites. See any computational geometry text. Most GPS including those in phones and tablets have twelve receivers. The more fixes the higher the location accuracy. The key is a good view of the sky. *

The anomaly you describe is because the device is not keeping up. Most nav systems like Google Maps, Apple Maps, and Waze cheat. They assume you're on a road and will use available mapped roads as a hint. You can see this when you have navigation enabled and it tells you to take an exit you pass by. The map will show you on the exit for several seconds before jumping back to the highway you stayed on. That algorithm, to my understanding, gets "confused" with high rates of turn and takes a while to catch up. I have some guess based on work with Kahlman filters but I couldn't say exactly without seeing the code or at least the math. I don't think Google or Apple are likely to share with me. *grin*

ETA: * Celestial needs three LOPs because the math assumes altitude of zero. GPS does not make that assumption. Four LOPs for latitude, longitude, and altitude.

[sgrimm]

Originally Posted by bergius

We’re using a dedicated tablet on a fixed mount under the spray hood as our “primary chart plotter”. This device is a 8” Galaxy Tab Active, a waterproof “industrial” tablet I bought off eBay for 60€.



It is mounted where a stone-age (late 90s?) chartplotter used to be on the boat.



Ours is shaded by the spray hood, so haven’t seen this issue occur. Though admittedly we don’t sail in the tropics.



This is a totally valid point. Our B&G instrument displays get a lot brighter than the tablet. It has always been readable, though.

Newer Galaxy Tab Actives have a brighter screen, but they’re hundreds of euros more expensive than this older model (though still maybe half the price of a decent plotter). Maybe one day…



At least on Android the Navionics app has a “keep screen active” option that skips all regular power saving and keeps the app open.



These industrial tablets have pogo pins that can be used to power them in a more waterproof fashion than USB. The charging cradle cost more than the tablet (70€ vs 60€), but one could also build a DIY one.

I’ve had tablets with wireless charging in the past. That would also make waterproofing easy.



Totally agreed. You can also transmit other stuff to the tablet over WiFi, like depth and AIS targets. Using the ship GPS also reduces the tablet’s power consumption quite a bit.

On our boat this is all handled by Signal K on a Raspberry Pi that is connected to N2K (using a Sailor Hat). It also amends the N2K data with other non-marine sensors like Ruuvi tags.

I wish the Navionics communicated also in the other direction, sending active waypoints etc. But that’s just a convenience.

One cool advantage I saw with using the tablet was route editing. You can edit the currently active route on a phone (for example) while the tablet is navigating, and it’ll update “live”. Was handy when we had to move some waypoints around when Navionics autorouting wanted us to sail under a too-low bridge,

I have a similar setup with a Galaxy Tab Active with a RAM powered tablet holder. Powered through pogo pins and not USB cable.

It works amazingly well and I can quickly pop the tablet out and use it for other things when not navigating.

However, it's a backup to my Raymarine. One remaining drawback is GPS accuracy is sometimes not as good as my Raymarine with external GPS receiver. And I don't have depth or wind on my tablet. There are options but more cost.

So even though I have all this. I don't think it's as reliable as a purpose built Garmin, Raymarine, B&G system. But it makes a great second / backup unit.

[FoxIslander]

Used one of the larger iPads and iNAVx for 8 years on Puget Sound waters. Never once an issue. Tablet was under the dodger and stowed inside at night. Had a Garmin handheld gps as backup. Will do exactly the same thing once I find a boat.

[Auspicious]

I drove for sea trials yesterday on a SeaRay motor yacht. Steering station is pretty much a fly bridge with a hard top and enclosure. Built-in Raymarine RL80C with split screen radar and chart and Garmin 5212 with charts. All the charts were long out of date. My iPhone 12 was plugged in (Qi wireless) with Aqua Map and current charts. Home grounds so charting was more about courses than navigation per se.

Huge difference between brightness of the phone and the plotters. Even under the hardtop the phone was more difficult to see and washed out when the sun was behind us.

[makjeng]

I think most of the shortcomings of mobile devices have been well covered. Several years ago we had to return my Raymarine chart plotter to the factory for repair. For seeral months we got y on mobile devices plus a temporary sounder arrangement. We experienced most of the mentioned issues. Water proofing tends to magnify the overheating and screen visibility issues, and state of charge is an issue.
It is all about situational awareness and one important point to be aware of, if a small screen is being used, is potential ‘zoom errors’. Significant hazards might be just off screen as it is zoomed-in to help legibility. I have seen this problem in action first hand on a friend’s boat. The skipper said there were no rocks ahead and the crew could see the swell breaking about 1/2 a mile ahead. He showed us the chart on his phone to convince us we were were seeing things but a quick course change soon became necessary.

[Capt. Mike Maurice]

I gave up on paper charts about 10 years ago. I depend more on the charts in my cell phone than the chartplotter on the boat. I carry two phones with the same charts and software.
I carry an old Garmin GPS76. I know how accurate and reliable the equipment that I carry. I have no idea about the accuracy or reliability is of the equipment aboard the boat. And usually the owner knows less.

I have had new $25K chart plotting systems aboard the boat fail in the dark, near land in storm conditions. And the failure was not obvious and was carrying us into danger. The cell phone showed us within 1/4 mile of a rock awash, instead of the mile that the main system showed.

The weakness of cell phones and tablets has been well documented in other posts and should be believed. But, under conditions where a mistake could be fatal, I generally have both phones running and charged up at the same time. As well as whatever the boat has to offer. The lesson is: never depend on one single navigation device. If you are going to depend on your electronic toys, be sure you know them inside and out. Read the manuals, practice, practice, and practice...

Having redundant equipment and knowing your equipment well will lower your blood pressure, anxiety level, prolong your life, improve your metabolism, improve your eyesight and a thousand other useful, marvelous things. Which you can trade for reward credits!

If you aren't sold now, you never will.

[Capt. Mike Maurice]

The cell phone has one major advantage. You can practice with it, at home, in bed at night in almost complete safety, learning all of it's quirks and limitations. The chart plotting systems have so many features, bells and whistles, settings and options that I have come to the conclusion that not one owner in 1000 knows their installed chartplotter well.

[Bill_Giles]

I like to put a pencil mark on a chart and then look out and take soundings to confirm what the chart says. I really do not like the idea of my phone being the device to save me running into a rock. We run a Navionics plotter up top which is repeated below at the chart table. There is also an iPad running some charting software. In my sailing career I have had GPS fail twice, once it was the onboard aerial and the other it was a complete GPS blackout. We tried three different devices to no avail. Two hours later it came back up no problem.

At least if you have charts and maintain an hourly log then the worst that can happen is you are 59 minutes from your last known position. Given your course, speed, tides and leeway you can know pretty much exactly where you are and not heading for a sunken rock.