Contents: Myth busting

Is a smartphone OK for serious navigation?
Don’t I need a phone signal?
Won’t bad weather stop GPS working?
Doesn’t the US government degrade civilian GPS accuracy?
Don’t Mountain Rescue advise against using phones?
Sarloc and PhoneFind

Is a smartphone OK for serious navigation?

Yes. I’ve owned a clutch of different dedicated GPS devices and three smartphones. My favourite all-round navigation tools have been the smartphones, by some margin. They are light, easy to use, fast and have great screens. A modern smartphone might have a better GNSS receiver than some GNSS handhelds and good positional accuracy is a given. See Handhelds vs smartphones.

Most modern phones will receive signals from more than one of the global satellite systems. This speeds up getting a fix, helps with accuracy and the unit will do better when conditions are difficult.

eg   A Samsung S10e phone picks up satellites from all four of the current global satellite systems. An iPhone 12 uses three global systems (GLONASS, Galileo and BeiDou) and adds the regional QZSS too. Some Google Pixels, Asus Zenfones, Nokia phones (and others) provide all six constellations currently in service. None of the older Garmin handhelds offer more than 3 global constellations. Some early handhelds that are still in use will only access the American system.

In many ways our modern smartphones are much better than dedicated GPS handhelds for navigation. Navigation apps can take advantage of a phone’s powerful electronics and touch screen, converting the phone to a slicker, more sophisticated instrument than many dedicated devices. The best apps provide excellent planning, navigation and tracking tools, usually with a raft of other goodies too. Smartphones can carry as many maps as you could want and with the right app you can use any map at all. Their internet connectivity makes planning, importing and the sharing of routes easy too.

It’s not all roses. Typically, smartphones aren’t very rugged, touchscreens may be ‘jumpy’ in the rain and without care the batteries won’t last long. However these problems are easily overcome.

If you’re a recreational adventurer, then a smartphone-plus-protection can do a great job.

Don’t I need a phone signal?

No phone signal is required. Honest. This might be the most common concern about navigating with smartphones and a few people will be vocally anti-smartphones for this reason, but they’re wrong.

Inside nearly every smartphone made since 2007 is a dedicated GNSS aerial and a GNSS receiver (a tiny electronic ‘chipset’) that picks up signals from overhead GNSS constellations without any help whatsoever.

A phone’s GNSS receiver doesn’t need a mobile phone signal, an internet connection, Wi-Fi or Bluetooth. All really can be switched off and the GNSS receiver will still pinpoint the phone’s location. Any navigation app on the phone can use the position provided by the GNSS receiver.

To be crystal clear, a phone’s GNSS receiver works in exactly the same way as a receiver in a dedicated GNSS handheld. No phone signal required. GNSS receivers in modern phones are likely to be better than the receivers in older dedicated GNSS handhelds. If a phone’s working, then it can provide a very accurate position.

This myth may persist because satellites aren’t the only way a phone can get location information. Phones can also use cellphone masts and WiFi to help locate themselves. Also, satellite orbit information that would normally be downloaded from the overhead GNSS satellites can be delivered to a smartphone more quickly via the internet. This is called Assisted-GPS (or A-GPS). These things may help reduce the time the phone needs to get a fix but don’t offer any more accuracy, and they are not needed.

Another reason this myth persists is less-experienced digital navigators will head out into a cellphone signal-free area and lose their mapping. Many navigation apps default to online mapping and will work fine until the phone signal disappears. The mapping must be downloaded to the phone so that it’s stored on the phone’s internal memory. Then the phone can use the stored mapping which frees it from the internet. Just like a dedicated handheld from Garmin or a car satnav.

A phone can be anywhere on earth and benefit from GNSS accuracy. No phone signal required.

Won’t bad weather stop GPS working?

No. Positional accuracy is good, whatever the weather. The frequencies used for GNSS signals were deliberately chosen so they would survive terrible weather intact. For those of us who live in the UK that’s good news.

The European GNSS Agency (GSA) asked GNSS experts working in Antarctica to comment on how the Galileo system is affected by bad weather. Note the second paragraph in this relevant extract from the article…

From the FAQ at https://www.navcen.uscg.gov/
GPS is a satellite-based radionavigation system developed and operated by the U.S. Department of Defense (DOD). GPS permits land, sea, and airborne users to determine their three-dimensional position, velocity, and time 24 hours a day, in all weather, anywhere in the world with precision and accuracy far better than other radionavigation systems available today or in the foreseeable future.

Tech-heads can see just how little bad weather affects the GNSS signals here.

Doesn’t the US government degrade civilian GPS accuracy?

No. However, many years ago this was possible. In the 1990s a thing called ‘Selective Availability’ could be switched on to spoil the accuracy of consumer GPS units. At the time ‘SA’ could add a 50m horizontal error and a 100m vertical error. In May 2000 Bill Clinton ordered it to be turned off permanently. The US government’s official website (GPS.gov) says ‘The United States has no intent to ever use Selective Availability again’.

Our consumer units have benefitted from great accuracy using GPS ever since.

Today, even if the American GPS was switched off entirely, most modern GNSS receivers would carry on working using satellites from one or more of the other global systems.

Don’t Mountain Rescue advise against using phones?

It’s not unusual for mountain rescue teams to criticise hill walkers who have relied on smartphones for navigation. Note the word ‘relied’.

That criticism isn’t (or shouldn’t be) of a smartphone’s ability as a GNSS device but on the wisdom of having no backup. Dropping a phone onto a rock could break it, winter cold can quickly kill an old battery, bad weather will ruin an unprotected phone and many techie phone issues can spoil your day. However, if you understand a smartphone’s limitations and take appropriate backup then you can safely enjoy the amazingly accurate guidance it provides. However many backups you take, make one a map and compass. They are very reliable and can’t be ‘jammed’ by the military.

If you’re in a party you could easily have a few GNSS smartphones/handhelds and maps and compasses too. The more the merrier. You can’t have too many backups.

Here are some tips from Mountaineering Scotland.

SARLOC and PhoneFind

In many mountain rescue incidents it’s a lost party who initiate the call-out themselves, using a smartphone. Mountain rescue teams can discover exactly where that smartphone is, using systems like SARLOC and PhoneFind. 

Both work similarly. The mountain rescue team send a short text, which includes a web link, to the mobile phone.  The lost recipient only needs to tap on that link, and if the phone’s ‘location services’ are on and the phone signal can provide a data connection for long enough, their phone will send its GNSS location to the mountain rescue team. The location provided by the phone is GNSS-accurate, so mountain rescue can find the lost party even in horrible conditions.

According to a June 2018 article about SARLOC in UKClimbing.com; between May 2011 and June 2018, SARLOC had been used 1600 times. About 230 times every year.

Notice that in every one of those incidents, the phone that initiated the rescue could have successfully guided a lost group to safety, if only it had been loaded with a navigation app and map.

In nasty weather, it must be extremely hard to find someone in the mountains if they can’t be located by SARLOC or PhoneFind. Lives are lost.

Put an app and map on your phone. You can’t be lost if you know exactly where you are.