Self portrait with GPS

Recently, one of Journeys, &c’s most loyal readers asked about choosing a GPS solution for hiking. Though far from expert, I’ve had a bit of experience using GPS, including to save my bacon on at least one occasion.

The trick with GPS is to know how to survive without it. Once you can do that, it adds a welcome margin of safety and convenience to your trips. Read on for the Journeys, &c take on this great technology.

Delta rockets similar to this one launched seven GPS satellites in 1989-90 (NASA public domain)

First up, what is GPS?

It stands for Global Positioning System. In its essential form, it is a system that can tell you, with great accuracy, where you are, and which way to travel from there to somewhere you want to be. More sophisticated versions, like the one in most modern cars, can use GPS data alongside maps to give you route information (turn left in 50 meters…). But for hiking, most people will use the purer form of the system, which tells you where you are and points you towards where you want to be.

The US government operates the Global Positioning System. Others exist – Russia’s GLONASS, which is fully operational, and China’s BeiDou and Europe’s Galileo, both under development. This post just discusses GPS, though you can buy receivers for the other systems too (and some will take data from more than one, like the Garmin eTrex20/30 which can connect to GLONASS).

How does it work?

Remember trigonometry from high school? Something about triangles, right? Yeah, me neither. Algebra and calculus are undoubtedly involved too. The simple version is that there are 31 satellites up in space, and at any moment from any point on earth, at least four of them should be overhead (usually more, and the more the better). They know, to extreme precision, exactly where (and when) they are. They beam out this information as a signal.

This great diagram shows how the “constellation” of satellites orbit the Earth, and send down their signals (red lines) to be picked up by a GPS receiver.


(Shared via Wikipedia under Creative Commons Share and Share Alike 4.0, created by Paulsava)

Your GPS receiver picks the signals up, does the maths, and triangulates your precise position. It then converts this information into something you can understand and interpret – like latitude and longitude or specific grid coordinates to match a map.

My old Garmin GPS12 shows my position in lat/long, as well as my altitude, the distance covered so far, and my last heading (192 degrees)

This is the colour screen of my eTrex20. It’s displaying the position using UTM format (grid 55H, then the east and north grid coordinates, at the top. The top right hand box shows “3m”, the predicted accuracy. The number 636m in the middle right is the current elevation. The middle shows the GPS satellite constellation and in this “simulation” mode, it’s showing good signal strength from all satellites, which is not a real world occurrence!

Civilian GPS is generally accurate to within a few meters. A variable error is added each 24 hour period, meaning that positional accuracy will be perhaps three meters one day, two the next, and somewhere in between the day after that. Military GPS doesn’t have this limitation. Certain high-technology civilian GPS solutions (like differential GPS) can correct for this error, but it’s impractical (and not really necessary) for hiking purposes. After all, if you can’t find something within a few meters of where you are, you probably have other, more pressing problems. As always, you also need to use your other navigational equipment – notably your eyes and brain – to locate your position and the best route to your destination.

These are the 1990s-era US military handheld GPS receivers. They weigh 1.25kg compared to the 0.15kg of a Garmin eTrex 20. The extra weight buys you more ruggedness and greater accuracy, as well as anti-jamming capabilities. The newer military unit is about 0.45 kg and even more jamming-resistant (US military image, public domain)

How do you use the data from your GPS?

The most basic way is to read off the position data from the screen, and then look on a map to see where you are. Another way is to punch in the position coordinates for where you want to be, and command the unit to tell you how to get there. It will give you a direction, or “bearing”, and usually can display an arrow which you follow while holding the device in front of you. There is a lot more to learn about using GPS, but the first step is choosing a device. We’ll cover the rest in another post.

How to choose a GPS

For most people, the choice about GPS for hiking boils down to this: dedicated unit, or cellphone app. There is a growing market of smart watches and GPS enabled watches, about which I have little knowledge. Here is a basic summary:

Device Pros & Cons Examples
Handheld GPS Rugged, long battery life with easily-found and carried AA cells, effective and reliable; dated interface, low res screens Garmin eTrex series
Cellphone Apps Good screens, often more modern interface, apps often free; phone battery life very short in real conditions, hard to recharge in wilderness, touchscreens inconvenient in cold, phones not ruggedised GaiaGPS, or very basic data only on GPSCoordinates (Android)
GPS watches Compact, yet multi-featured, decent battery life; very small screen, harder to enter data in the field, hard to recharge in wilderness Suunto Traverse

Be warned that GPS watches like the Seiko Astron simply keep time via the GPS signal. You can’t use them to navigate (which should be obvious from the second you see one).

The internet is FULL of arguments about whether a dedicated GPS unit is better than a smartphone.

Here is my view.

A dedicated GPS is generally superior to a smartphone for any serious navigation in the hills. There are several reasons.

Battery life: navigation apps on smartphones can quickly drain a device’s battery, especially if it also being used to make calls and take photos and post them on WeChat or WhatsApp. Some people claim to get three or four days out of their cellphones but that’s in airplane mode, low brightness, and without using any other apps. A GPS unit, by contrast, can get up to 24 continuous hours from a pair of AA batteries (so if you shut down overnight it should be good for nearly five days). A smartphone can readily be recharged out in the hills with portable lithium batteries, but these are also generally heavier than a spare pair (or two) of AA batteries. The AAs are cheap and can be bought just about anywhere, even in some smaller villages near the Great Wall (for example).

Cold-weather use: most smartphones use a touch screen interface, as do some higher-end GPS units. If you are hiking in winter, you will be amazed how quickly your hands get extremely cold without gloves (it can take as little as 30 seconds). If you need to regularly remove your gloves to operate a touch screen, you will quickly get cold and uncomfortable. GPS units with pushbuttons or rocker switches can be operated wearing gloves. Battery performance for all types of device is poor in extremely cold conditions. If you use a dedicated GPS unit you can comfortably keep a pair of AA batteries in an inside pocket close to your body warmth. Of course, both types use LCD screens so eventually it will get so cold that these freeze. By then, you probably have more on your mind!

In really cold weather, anything with a screen stops working. It was minus 25C this day, and that *was* a first-gen Redmi.

Ruggedness: it’s hip, apparently, to have an iPhone with a smashed screen, but what that really tells you is how fragile smartphones are. Most dedicated GPS units are waterproof and slightly ruggedised (though a direct hit on the screen will probably break it). A related point is longevity. I used the same Garmin GPS 12 that I bought in 2000 right up until 2013, when it finally died. Know anyone who still uses a smartphone from even five years ago? A decent GPS unit is a good investment which you can amortise over a long period of time. As long as AA batteries can still be bought, and the satellites themselves remain in orbit, you should get many years of useful service from it.

NAVSTAR IIF is the current generation of US GPS satellite (USAF public domain)

Where does the smartphone beat a dedicated unit?

A smartphone is far superior to a dedicated GPS for navigating while driving. Dedicated GPS units, other than very new high-end ones, do not offer the turn-by-turn route mapping and updating and voice cues that even a basic smartphone app can give you. Whatever you use out in the hills, a smartphone is best for driving there.

Many users, especially if they go from a smartphone to a GPS, find GPS screens to be low resolution, and miss the intuitive interface of a smartphone. With a decent navigation app, a smartphone can function for actual navigation as effectively as a dedicated unit, leaving aside the given the practical disadvantages set out above.


GPS units, including the Garmin eTrex 20 I use, are regularly criticised for not coming with pre-loaded maps and for the price of the after-market map downloads. This is entirely irrelevant to me as a Great Wall hiker, as there are no maps of sufficient detail available anyway. Wherever you hike, it is pretty straightforward to develop your own routes, waypoints and landmarks on Google Earth and transfer them on to your GPS unit (eg using Garmin’s free BaseCamp software, or the software that comes with other brands of GPS). On many units you can also upload satellite imagery. Where topographical maps are readily available, you should use those as your primary source of information. The GPS is best seen as a tool for placing yourself somewhere on that map.

Garmin’s “BaseCamp” software shows the data from the GPS unit. The waypoints were selected in Google Earth and exported to BaseCamp – a simple process. Within BaseCamp, and also on the device, I can choose the icons. The blue line is a trace of my hike, and the black lines are traces of another trip (top) and a route I plotted on GE (bottom).

This is the same area in Google Earth, showing two traces (yellow and blue). The red line was not imported into BaseCamp, but the red pins were, and became the green dots on the BaseCamp screen.

Here is the same Great Wall area on the eTrex20 screen. The GE data was uploaded via BaseCamp.

As an aside, this is another area on my old Garmin 12. Comparing this to the eTrex20 colour screen shows in an instant why you’re better off paying a little more for colour screen (rather than the b/w of the cheaper eTrex10).

Where available, proper topographical maps are a great help. This one is an extract of a 1:50,000 map of the Mt Bimberi area near Canberra, Australia. Gridlines are in the UTM format, rather than lat/long as on the BaseCamp screenshot. A GPS device can be set to display a range of coordinate formats.

In practice, it’s a lot simpler to use a paper print out (of the Google Earth image, say) at a decent size, or just use a proper topographical map if one is available. Either option is a useful backup if you lose, drop or forget your GPS or smartphone, or if either of them runs out of juice. Apart from that, navigating to a waypoint described by coordinates you’ve programmed in will give you a better understanding of what navigation actually involves than simply pointing to a spot on a downloaded map. Generating your own map means you understand where each waypoint is in relation to other landmarks. This situational awareness is vital to safe navigation, because inevitably, your device Will. Fail. One. Day.

You need to know what to do when that happens.


I personally would avoid GPS units that operate with touchscreens, for the reasons set out (and illustrated) above.

For any regular hiking longer than a day, I thoroughly recommend the Garmin eTrex 20. It has everything you need and not much you don’t (except the Geocaching features, seemingly inescapable these days, though you can safely ignore them). The more expensive e30 has a digital compass and altimeter, but the reality is that an e20 can give you your compass direction as long as you’re moving, and anyway you should carry a real compass for back up. As for the pressure altimeter, it’s very rare to need to know your altitude for navigational purposes and any GPS will give you a fairly good altitude fix anyway (and besides that gives you a great excuse to buy a cool altimeter watch). The e20’s lesser sibling, the e10, comes in at under a hundred, but you really do notice the lack of a colour screen (see above).

I’ve been generally pretty happy with my Garmin eTrex20

In the US on Amazon, these eTrex 20s go for well under US$200 in January 2017 and are only getting cheaper.