An 'adventure' handheld GPS can reveal your position if you're lost, or record every step you take so you can find your way back.
Also, if you know the co-ordinates of a destination, anywhere in the world, it will show you how to get there on foot.
- Handheld GPS devices can help you get back from a long walk in the bush, but take along a compass, a good map and some common sense - just in case.
- Saving points along your journey can be invaluable for future visits, whether it's a dangerous cliff face to avoid, or a fantastic restaurant you stumbled upon in Bahrain.
Handheld GPS work by collecting information from a group of at least 24 satellites that constantly orbit the earth. A fix on three satellites is all you need to get a 2D position, with a fourth needed to calculate height. So unless you're inside a building or at either the North or South Pole, most units will help you find your place in the world.
Unlike some of the latest mobile phones with inbuilt GPS features, handheld GPS units don't need a mobile phone network to work, and unlike a car navigation device, they don't need an electronic map to be useful.
A handheld GPS continually monitors its own position and speed, ready to give you information on where you've been while you're carrying it, and where you should go. They are portable and designed to be carried for extended hikes.
Some units are similar in size to a rugged-design mobile phone, with several small buttons and a joystick to control the various settings. Some units are larger, with a bigger screen and wider buttons.
Saving a waypoint — such as a river crossing, interesting rock formation or even hard-to-find bookstore — is an ideal way to record any route markers or points of interest when you're out walking (they're called points of interest on car GPS units). Simply press a button or two on the unit. If you want it to record the entire journey, a tracking feature creates a snail-trail that evolves as you move. Once a track is created, you can save it as a route to use later or to guide you back to your original position.
Most units also have an alarm to let you know when you've arrived back at the starting position and if you move too far off the saved path.
If you have large hands, or are off to a colder climate and plan on using the GPS with gloves on, a larger unit could be a good option.
Some Handheld GPS have no mapping capabilities, but have a very good electronic compass and could indicate not only the barometric pressure but also the rate of change effectively giving you a portable weather station. This will probably lower the battery performance compared to other units due to the fact that they will be constantly collecting barometric pressure information, even when turned off.
Mapping at home and in the field
Handheld GPS come with a basic world map, but you can't get a detailed electronic Australian topographic map without shelling out a bit more cash.
Some units have only one option: the DiscoverAus Topo SD map. This isn't cheap, at around $400, although it does provide impressive contour details, accurate to 5m. Some units use the Tracks4Australia ($180 with 20m contour intervals) or Topo Plus ($129 with 10m contour intervals). Some units have some fantastic US topographic maps — but that's not much help for us down in Australia.
Electronic topographic maps are contained on a removable flash memory card and provide very good detail on surrounding areas and contours, but the small screens of some units make it difficult to gain a wider view of the area. Higher-resolution screens on the provide the best readability of the compact units.
Some units claim support for additional marine navigation maps for those with a nautical bent. These give good depth information as well as details of buoys, lighthouses and anchorages.
You can also use a map program on a PC to set waypoints and routes at home before you head out, and if you want to show off what a hardy bushwalker you are, you can upload routes back to a map on a PC to show where you've been. All units we looked at can use mapping software on the PC, but while it's standard on most, it's an optional extra for some. Check before you buy.
All the units we looked at performed accurately when getting a fix on the required number of satellites, with differences ranging from around 3m to 12m. A wider range was observed when trying to calculate altitude, with some out by a significant 42m. However, it's generally more important to know where you are than how high you are.
Under a clear sky, you should expect handheld GPS units to take no longer than a minute to locate their position. However, when confronted with dense foliage, they vary in the time taken to get a fix.
Some units are powered by a rechargeable Li-Ion battery, which initially caused concern due to the inability to get spares out in the field. However, a AAA battery adapter that comes standard in the box is seen as a good all-round solution.
Most of the other units can use either rechargeable AAs or normal alkaline AA batteries. While a handheld GPS provides very accurate recordings of individual waypoints and treks, we recommend carrying and learning to use a compass and paper topographical map as backup for anything longer than a short hike.