Contents: GNSS watches

Pros and cons
Why use a watch?
Route planning
Off-route alarms
Screens (MIP vs Amoled)
Battery
GNSS receiver accuracy
Maps
Weatherproofing

Apple smartwatches

Pros and cons

Pros

• Convenient for following a highlighted route.
• Rugged and weatherproof.
• Great battery life.
• Good for recording tracks.
• Off-route vibrations and/or audio alerts are options.
• The small battery charges relatively quickly and takes little from a power bank.
• Impossible to drop.
• The battery is less affected by winter cold.
• Good free or cheap topo maps for the world are available for Garmin watches.
• Wireless connectivity is convenient for transferring files to and from the watch.

Cons

• Expensive.
• A tiny screen is poor for map browsing and getting an overview of the topography.
• A clunky interface and small screen make a watch a very poor planning tool.
• Waterproofs and gloves make the watch less convenient to view.
• The battery needs charging when flat. You can’t just pop a pair of AAs in.
• Screen detail is small and requires good eyesight.
• Button operation is slow compared to the better interfaces on phones and handhelds.

Why use a watch?

It’s very convenient to have a highlighted route, on a moving map, on your wrist. If the highlighted route is going through the heading bug in the centre of the screen, then you know you’re on course. Watches like the Garmin Fenix range will give off-course warnings when navigating. A vibration on the wrist, an audio alert or both. Get about 30m off-route and you’ll know about it. It’s hard to go wrong. Stay on the line and you’ll successfully navigate the day away.

Battery life is typically great and the best watches outperform most handhelds easily. Garmin claim up to 110 hours for the Enduro 2. That’s whilst running the GNSS receiver constantly and without any extra help from the built-in solar screen. Adventurer and tech-gear reviewer ‘DC Rainmaker’ donned an Enduro 2 to hike the Tour du Mont Blanc. He hiked and navigated the entire 170km over eight days, on a single charge. The Enduro 2 was able to record a track of the whole route along with other data provided by other active sensors on the watch. Here’s his review.

I have used the lower spec Garmin Fenix 6X Pro. It has a smaller battery than the Enduro, but on a single charge it did all the navigation and tracking duties for a five day wild-camping trip around the Lake District. Garmin claim that the GNSS receiver can be run continuously for up to 60 hours using the American GPS constellation only.

Those are the great strengths of a watch. Convenient wrist-mounted navigation, tracking without battery anxiety and no worries about the watch surviving the weather or being dropped.

However, there are many watches armed with a good GNSS receiver that don’t include mapping. These aren’t much good as standalone navigation aids. They may run apps on the watch that will link with navigation apps on a paired phone, but I’m not going to talk about those. If you have to use your phone for the navigation to work then some significant advantages of the watch are lost.

If you want a watch for navigation then get one which stores detailed topo mapping on the watch.

Route planning

With a relatively clunky interface and a small screen, a watch is not not the best tool for route planning and plotting. If circumstances forced a change of plan whilst navigating off-grid, it could be a tediously slow process to plot a new route.

Garmins can auto-route to a given destination if the watch is using a ‘routable’ map but this won’t necessarily plot the route you want to take. It’s a good idea to take a paired phone with you. Equipped with an app like OsmAnd, a phone can provide fast snap-to-path plotting away from any internet connection. Transferring a phone-plotted route to a Garmin watch can be done directly using bluetooth.

With a highlighted route on the map some of the small screen disadvantage goes away. ‘Stay on the line’ to be confident of being bang on course. Come to a decision point like a path junction and a brief glance at the highlighted route shows which branch to take.

Without a highlighted route then navigating with such a small screen is a poor experience, improved slightly with a touch screen. If all your other GNSS nav devices failed then it would get you out of trouble, but anything with a half-decent screen would be better.

Off-route alarms

Watches like the Garmin Fenix range will provide an audio alert and/or a haptic vibration if the watch gets about 30m off-route. If the wearer misses a turning or wanders off the plotted line then they’ll be alerted to their mistake. It’s hard to go badly wrong.

Screens (MIP vs AMOLED)

Screens are responsible for one of the bigger drains on the watch battery. All other things being equal, a watch with an MIP transflective screen will last much better than one with a power-hungry AMOLED screen.

AMOLED
AMOLED screens are like those found on regular smartphones. The LEDs on the screen use power to illuminate them. A bright pixel needs more power than a black pixel. Currently, for the same screen size an AMOLED display will have more pixels and a wider colour palette than an MIP screen. These screens will look bright and colourful indoors. An AMOLED screen will look less good in bright sunlight. These are not the most power-efficient watch screens. An AMOLED screen will typically not stay permanently illuminated but be ‘woken up’ by wrist movement.

MIP
Transflective Memory In Pixel (MIP) screens allow ambient light through the screen. It reflects off a reflective layer behind an LCD image, illuminating it in the process. The more ambient light that falls on the watch screen, the better it looks. They look good in bright sunlight and are harder to see indoors in low light conditions. However, these watches have a backlight which makes them perfectly visible when ambient light levels are low. At night they are visible in the light from a headtorch too.

These screens are much more power-efficient than AMOLED screens and can stay on all the time. Significant power is only used to change pixels from one colour to another. A static image will consume very little electricity. However, they don’t have such a broad colour range as AMOLED screens and may not offer such a good resolution either. However we are unlikely to be watching videos on our watches. The colour range is wide enough to display maps well.

eg The 51mm diameter Garmin Fenix 7X sapphire solar has an MIP screen. The screen resolution is 280 x 280 pixels. The 51mm Garmin Epix Pro (Gen 2) – Sapphire Edition has an AMOLED screen that’s exactly the same physical size as the 7X but has a 454 x 454 pixel screen. Better.

If you want your battery to last as long as possible then get an MIP transflective screen. If battery life isn’t a concern and you like the vibrancy of an AMOLED screen then maybe that’s a good choice for you.

I sometimes go on multi-day hikes in the hills and want to charge my watch as little as possible. A battery-saving MIP screen was an easy choice. It works well as a navigation tool and can do a whole week’s worth of navigation with the map on screen the whole time. However, if your activities mean it’s easy to charge the watch when you need to, then you might opt for the vibrancy and better resolution of an AMOLED display.

Battery

The battery capacity of a watch will be a fraction of a smartphone battery. It doesn’t take much out of a power bank to have a watch fully-charged again and small batteries don’t take many hours to charge either. The Garmin Fenix 6X Pro is 400mAh, about a tenth the size of a flagship smartphone battery.

If you opt for a smaller screen watch then expect the battery and battery life to be commensurately smaller.

Perhaps an unexpected benefit of a wrist mounted watch is that battery life is less affected by winter cold. Strapped to a wrist, a watch stays warmer than a shoulder mounted handheld or a phone-in-a-pocket.

GNSS receiver accuracy

Under an open sky there aren’t significant differences between a watch, a smartphone or a dedicated handheld device. Which technologies the watch receiver uses will determine how accurate it is. eg A watch using a dual-frequency GNSS receiver and multiple GNSS constellations will be reliably more accurate than a normal receiver using just the GPS constellation. However, all will be accurate enough to provide excellent off-grid navigation for activities like hiking.

Here’s a section of a track recording made in the Lake District with a Garmin Fenix 6X Pro. This contains an older single-band receiver using two constellations (GPS + Galileo).

Much of the time the path is hard to see because it’s directly under my Fenix recorded track. That accuracy is typical, normally only disturbed by nearby cliffs, dry stone walls and trees etc
You can examine the full track here. Select satellite imagery in the map layers and zoom in for a good look.

Maps

Pay attention to what’s offered. Even if the provided mapping contains contours it won’t necessarily contain the detail you want. Try and find independent reviews providing knowledgeable informed comment on any supplied mapping. eg Google maps, OpenStreetMap or similar may be offered but are not appropriate for off-grid nav.

The Garmin mapping watches are a safe option. You can get very good OSM-based topo maps for Garmin watches for free, or very cheaply, from third party map-makers.

John Thorn is an independent map maker who produces a map of the whole of Britain for about £15. It contains OS ‘terrain 50’ contours, the OS opendata crag detail is the same as that found on the 1:25k OS Explorer maps. It includes public rights of way, marks open access land and shows OSM paths too. See the phone screenshots below. Johns map marks extra paths that aren’t on the OS map. 
John Thorns OS/OSM combination map of Britain

It’s the same map that John offers for Garmin devices.

OpenTopoMap offers completely free OSM-based maps for Garmins. These are Garmin compatible versions of the OpenTopo web map which you can view here. Download the map file and the contours file. Put both on the watch and enable both.

TalkyToaster offer a good topo map of Britain for a donation, and for about £15 a more detailed 100% OSM-based routable map is available. Many other countries are also available, at similarly cheap prices.

Weatherproofing

Check water and dust ratings of any watch you’re considering but typically they will be good. GNSS watches are designed to be used outside. They should be properly weatherproof. Many will be good enough to wear whilst swimming.

Apple smartwatches

The 2023 models come with good multi-band GNSS receivers but still don’t provide good onboard topo maps. The battery life on the watches is not so good as the best Garmin and Coros watches. On an older Apple watch, if the GNSS receiver is left running for navigating it probably won’t last a long day.

There are a couple of third party apps for the Apple watch that enable the use of downloadable topo maps that are stored on the watch. These apps will highlight routes on the mapping using imported GPX files. The Apple watch then becomes a good standalone GNSS navigation device, albeit with a battery life that needs monitoring. Take a look at the Footpath app, this offers OS maps and other government-funded maps from around the world. Work Outdoors offers OSM-based topo mapping.

Mountain guide Chris Hazzard aka ‘Hiking Guy’ reviews the Footpath app and shows how to use it. He does a how-to for Workoutdoors too.

Other watch nav apps are also available to pair the watch with the phone. eg OS Maps, Komoot and Outdooractive. However the watch then becomes a screen and interface for the phone app which must be running on the phone. The watch isn’t behaving as a standalone device and the phone battery is getting flattened. It might be convenient on a short day but you could just use the phone.