Satellite accuracy on a mobile

How accurate is the position calculated by your smartphone? As mentioned in the previous post, the Royal Institute of Navigation is sceptical. Its new book on electronic navigation for leisure sailors says: “At sea, mobile phone positioning uncertainty will typically be several hundred meters or more, which may be enough to put us into danger”.

I am looking for some proper studies on this issue, because I am sceptical about that statement. In the meantime it’s easy to check what your phone tells you about its own location performance when it relies only on satellite signals.

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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 I think they may be out of date on this narrow point of phone accuracy, which I’ll come back to in a later post.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.

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February – averting satellite disaster

The British government turns out to have been ahead of the game on the  satellite risks I mentioned last month, with a £36 million programme just announced to  prevent navigational satellite failures damaging the economy by as much as £1 billion a day. It is feared that the entire country has become over-dependent on a handful of satellite systems.

Emergency services, the energy grid, mobile phones, Satnav, broadcasting and other communications, the Stock Exchange and an array of other activities all rely heavily on the super-accurate timing provided now by navigational satellites such as GPS and similar systems. There are life-threatening risks from failure, says the government.An image of a third generation Lockheed Martin GPS satellite

The new investment is in a National Timing Centre to create a network of super-accurate atomic clocks around the UK, accessed through ground-based communications, so that the economy will no longer be over-reliant on timing from GNSS signals from the sky.

GNSS is the term that embraces the US  GPS, the first system, Russia’s GLONASS satellites, Europe’s new Galileo and also a rapidly developing Chinese system.

Galileo failed completely for a while last year during its start up phase, because of operator errors, and there are now many examples of interference with GNSS systems and malicious ‘spoofing’, in which navigation instruments are fooled into thinking they are somewhere else. The heart of all navigation by satellite is accurate timing, without which positions cannot be fixed.

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