Are phones reliable for navigation?

The Royal Institute of Navigation’s excellent new book on electronic charting is pretty tough on the use of smartphones as chartplotters, claiming their accuracy can be as poor as 200 metres or worse. I think they may be out of date on this narrow point of phone accuracy, which I’ll come back to in a later post. But in the meantime I’ve had a demonstration of a different smartphone problem, one I had not focussed on before: unreliability in cold weather.

One of the nicer things about lockdown (if there are really any at a time of rampant virus) is to go most days for long walks in the winter cold, which is how I discovered that my phone seriously dislikes low temperatures. Not just sub-zero, but any day with temperature near or below zero. When there’s a strong, chilling wind it even goes on the blink in an outside pocket with the temperature in high single figures.

It’s clearly a temperature effect because putting it inside my shirt gets it working again in minutes. When I take it out, after a few minutes it soon blinks again, literally, with the screen flashing rapidly. At sea in cold weather, which means an awful lot of the time around Britain unless you sail only June to September, this would be a real concern with a smartphone.

Mine is not a new phone, and I have no idea whether this is highly unusual or something to expect. Maybe it’s my fault for being a stick in the mud who keeps a phone (once top of the range) for nearly 4 years. But its battery is still performing well in higher temperatures, lasting 18 hours with some browsing as long as I don’t take photos, and this lulled me into false security about it’s navigational use.

For me, it certainly confirms the advice you hear in hiking and trekking circles that mobile phones are not really up to the job and you need a specialist instrument. My phone would be completely useless on Scafell or Ben Nevis on a cold April day.

When operating in satellite navigation mode only, without corrections from phone masts or nearby Wi-Fi, there is also a separate aerial issue. My phone does not receive satellite signals well when stored upright in a pocket, as I found on the boat out at sea, where it would take quite a while to locate itself again. It has to be taken out and held flat to find a position.

[Update after another long walk, this time with the sun out, temperature above 10 degrees and the phone working properly: the aerial issue turned out to be nothing of the sort. It was a phone settings problem, caused by the screen going to sleep and switching off the satellite connection. I thought I had changed to a setting that allows the navigation app to stay awake when the screen is off, but I had not done it properly. I’ve now changed settings so that my map app continues to function. However, I still have a strong suspicion, from checking as I walked, that the phone’s position readings are less accurate when it is held upright.]

I’ll keep checking my phone performance, but if I were to start seriously walking in the hills I’d buy a dedicated instrument. I am even less likely now to use a phone as a main backup device on the boat.

On Spring Fever, our mobiles have regular use as mini-chartplotters, but not for actual navigation, only for planning routes while sitting somewhere comfortable – preferably a pub – using the Navionics mobile app. You do not need all the missing navigational features for that.

Our serious backup, in case of chartplotter failure or flat boat batteries, is three separate tablets. We used to have on board a laptop run from the boat batteries, but the tablets have independent power sources, are more robust and easier to manage, and two have inbuilt GNSS receivers. The third has a plug in aerial. Having three also allows us to keep charts from different publishers for cross checking.

The only circumstance in which the phones would come into their own as backups, which I don’t like to dwell on, is if we have to take to the liferaft one day. They are just about the easiest things to grab and put in a pocket, and my Samsung is water resistant, claiming to be protected for up to half an hour at 1.5 metres deep, unlike the tablets.

For walking, I bought UK Ordnance Survey maps through Anquet’s OMN3 app at a cost of £32 for a 2 year subscription. I expected it would be a doddle compared with C-Map, Navionics, VMH, Imray, Antares and other electronic charts I have tried, but it has interesting features that made me think again. I am still trying to get properly to grips with it.

Functionally, it is the same as a raster navigation chart – so looks much the same as a paper version – but it operates in 3 dimensions. Distance on a land map is a function both of horizontal motion on the map and contour gradient – if you climb an apparent mile over a flat map’s surface on a gradient of 45 degrees, your distance covered is more than 1.4 miles. The app calculates actual distance walked over the contours. We are in East Anglia, so not much opportunity to check that out yet!

Screen shot of a Lake District navigation page on the OMN3 app

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