When you are hiking, camping or climbing in the great outdoors, your handheld GPS can be invaluable for helping you find your way.

It can also be the key to uncovering new trails and nature spots, as well as your lifeline in an emergency.

Hikers are spoilt for choice, with GPS devices to suit every budget and requirement, ranging from Garmin’s basic but functional Geko 201 and eTrex H models to the feature-packed and ultra-sensitive Delorme Earthmate PN-40 or Garmin GPSMAP 60CSx.

Here is a rundown of some of the features you will need to consider when buying a GPS unit to use on the trail. Many of these criteria apply to devices you can use for other outdoor activities too:

• Reception: The most important feature of a GPS for hiking is the satellite reception. Basically, you need a device that continues to work even if you are walking under trees, next to hillsides and rock formations, or in river valleys and canyons. Look for a unit with a high-sensitivity SiRFSTARIII or MediaTek chipset, and you will be able to get a signal on your GPS handset from just about any location. (In addition to the high-tech models mentioned, the Garmin eTrex HC and eTrex HCx ranges all give you excellent reception and fast signal acquisition.)
• Channels: Most handheld GPS units have 12 channels, meaning that they can accept up to 12 satellite signals at any time. Some high-end models offer more channels, for example the Lowrance iFinder Expedition C, which has 16.
• Maps: With the exception of the most basic entry-level devices, virtually all GPS units these days display maps. When you’re hiking, a topographical map that shows the landscape in detail makes life a lot easier. A few models, such as the Garmin Oregon 400t come with topo maps of the United States pre-loaded, while others have different sets of detailed maps and basemaps onboard. Most units give you a USB port and a cable for uploading additional maps and other data from your PC and the Web.
• Waterproof and ruggedized: For outdoor use, your GPS should be water-resistant to the IPX7 standard, meaning that it can survive sitting in three feet of water for 30 minutes. This will protect it against heavy rain as well as being dropped in a stream. Devices designed to be used outside are usually also built to withstand vibration, knocks and drops, and often have a rubber casing and buttons that cannot be broken easily. Overall, handhelds tend to be less fragile than in-car GPS units.
• Screen: The screen size and type people choose often comes down to personal preference. It can be hard to read a map on a small display, so you should pick a device with the largest screen you would want to carry around. Color screens show map features clearly, and backlighting is also useful, but both features burn a lot of battery power.
• Black & White: Some hikers therefore prefer a black and white display such as on the Garmin Geko 201, which can also be easier to see in direct sunlight. Certain new models like the Garmin Edge 705 feature a transreflective color screen for optimum readability in any light.
• Touchscreen or rocker keypad: Despite their small screen size, more handheld GPS devices come with touchscreens now (e.g. the Garmin Oregon 400t). This makes it simpler to enter names and cuts navigation time. A rocker keypad like the one on the Garmin GPSMAP 60CSx is meant to be used one-handed, which is practical when you’re on the trail.
• Size and weight: An important consideration when you have to carry your GPS along with all your other gear. GPS units for hiking range from a couple of ounces to nearly a pound in weight. If you really don’t want to carry any extra weight and can live without having maps on the screen, you could go for a GPS made for runners, such as the Garmin Forerunner 405CX or the Suunto X9i.
• Battery and other power sources: A unit that accepts external power from a household socket or your vehicle’s cigarette lighter as well as using batteries is ideal. Lithium batteries are great, especially if the device also takes regular AA or AAA batteries that can be replaced on the go.
• Memory: You need at least 20MB of storage space for maps, waypoints and other data. Many of the more advanced GPS units now feature a microSD card slot for unlimited storage.
• Routes and waypoints: Entry-level models typically store 20 routes, and pricier units give you 50. Most GPS devices let you enter 500 waypoints (specific locations recorded by longitude and latitude), while the Delorme Earthmate PN-40 offers 1000.
• Tracks: Your handheld GPS builds a breadcrumb trail of your hiking trip as you go along. This makes it easy to get back to your starting point. Most also let you upload tracks to your PC and view them on topographical maps.
• Additional features: Several high-end units include an electronic compass that lets you see which direction you are going in, without having to hold the device dead level. A barometric altimeter, which is essential for climbers, is also fairly standard on upscale models. The Garmin Rino 530 HCx offers both of these, plus some unique and useful extras such as a NOAA weather radio connection and a two-way radio for communicating with other members of your hiking party.

Find out How to Use Your GPS on the Hiking Trail.