They're big, they're bulky, and they'll do a lot more than simply get you from A to B. Designed primarily for those who like to get lost in a sea of data rather than those with a terrible sense of direction, the new generation of GPS watches are all about pin-pointing exactly where you dropped the pace - or over-stretched yourself.

The plethora of features on each one - from altimeter and compass to heart rate calculators and virtual racer modes - will be overkill for many.

Runners used to rely on cheaper accelerometer watches to measure distance, and these types remain pretty accurate on flat, predictable tracks where the pace and stride is steady.

However, go off-road, through woods or up mountains where your stride is constantly altered and changed, and read-outs drastically reduce in accuracy.

Stride forward the GPS running watch, a new generation of gadgets that communicate with those 24 beloved satellites that orbit us and make-up the NAVSTAR Global Positioning System.

Able to determine your position to around 15 metres, record your speed on runs as long as 100k, and map your routes later on smartphone apps, a GPS running watch is the ultimate training instructor… until Google Glass comes along next year, that is.

Garmin Forerunner 910XT, £330

Best GPS running watches
Leading the race is Garmin's super slick 910XT

Available with or without a heart rate monitor attachment (a wristband that connects with the watch via Bluetooth, and which adds about £20 to the price), the 910XT in Garmin's extensive Forerunner series of GPS watches is probably the reigning champion.

Lasting an impressive 14 hours on each charge, the monster 72g 910XT records your exact position once a second in addition to speed, time, distance and pace. It uses a barometric altimeter to create accurate altitude and GPS, too - a combo that most watches of its type don't possess.

It's completely configurable and can be set up to let you know - by subtly vibrating - when it's time for a snack, or when you're on the verge of breaking a personal best. All data is wirelessly pumped into a PC for analysis.

As a bonus, this waterproof (to 50m) watch isn't just for runners; swimmers get stroke identification and count as well as time and distance swum.

It can hook up with a mountain of ANT+ accessories, including a heart rate monitor and footpod, and it's possible to swap between sports - running, cycling, swimming and more - at the touch of a button. One for triathletes, then, or anyone with multi-sport ambitions.

Suunto Ambit 2, £360

Best GPS running watches
Suunto's Ambit 2 is the perfect companion for trail runners

It's got triathlete ambitions, certainly, but this new multisport watch from Suunto is best thought of as one of the ultimate GPS watches for trail runners.

A tad bulky at 82g and 15.5mm-slim, the Ambit 2 uses a barometric altimeter as well as GPS to measure altitude - just like the Garmin Forerunner 910XT - and can be used as a simple navigation tool (routing, 'find back', coordinates and a 3D compass), even during a run, for up to 15 hours.

There's also a setting to stretch that figure to 60 hours if you're happy to record a position only every minute - a feature most suited to hiking - and there's more to suggest that it's not just running the Ambit 2 is interested in; sunrise/sunset and tide times are featured, as is a storm warning.

However, there's an interval timer and auto-laps for training, pace, speed (even vertical speed) and distance stats, temperature, and features for indoor and outdoor swimmers (it's waterproof to 100m), skiers and cyclists that can be toggled to instantly.

Able to attach to Suunto's footpod and heart rate monitor accessories via ANT+ (a data-heavy version of Bluetooth) connectivity, this trail running-centric GPS watch connects with the www.movescount.com/apps community to access around 5,000 home-baked apps. Also available is the Suunto Ambit 2 Sapphire, which, for an extra £100, adds a sapphire crystal bezel.