GPS means Global Positioning System. A hiking GPS is small handheld unit you use to receive signals transmitted by several satellites orbiting the globe and translates them into your precise location around the world. There are many makes and models of hiking handheld GPS devices on the market to choose from. In order to select one that I right for you, first decide on the functional features you want:
1. Accuracy – Theoretical GPS accuracy is to approximately 15 metres with more modern units having greater accuracy. You can get an accuracy 5 times greater if you choose a WAAS-enabled (Wide Area Augmentation System) GPS. WAAS is a US-based network of satellites. The European equivalent is named EGNOS (European Geostationary Navigation Overlay Service). To track satellites, GPS receivers use several channels. 12 or 16 channel parallel receivers are the most common today. They are superior to 6 or 8 channels as they can locate satellites far easier, particularly in built-up areas and in wooded areas or mountains. 12-channel or more is better.
2. System of Co-ordinate – Topographicalmaps use a grid reference to determine location, the most common systems being Lat-Lon and UTM. Both systems are accurate but ensure the hiking GPS includes the coordinate system of the maps you intend to use.
3. GPS Map Datum – A variety of map datum have been created as points of reference on various maps around the world. Ensure your GPS unit is set to the same datum your map references, most often shown in the map’s bottom left corner. Using the wrong map datum could result in distance errors up to 200 meters (600 feet) or more on the GPS display screen. This difference may have terrible consequences in a mountainous area and especially in poor visibility conditions.You should reference your GPS device manual to find out how to set the correct datum to match the datum on your map. When selecting your GPS, ensure it has all the map datum you will need to use.
4. Power Supply – When out hiking, an external power supply is of no use, replaceable or rechargeable batteries and spares are what you will rely on. Some rechargeable batteries may also be replaceable during your hike. In either case make sure the batteries have a long life. It is best to choose a GPS in which the batteries can be replaced on your journey. If you select a GPS device with a rechargeable battery that cannot be replaced with a spare during a hike then it is critical to ensure that it has a sufficiently long life. When out on the hills or in poor visibility conditions, you do not want to run out of power.
5. Display Screen – The brighter and higher the definition of the screen display screen, the easier it will be to read, particularly when the sun is shining. Colour display screen are generally easier to read than black and white, as is a larger screen. Generally speaking, larger screens and higher definitions are better but are more costly. However, bear in mind that a cheaper simple screen display is no good if you cannot read the displayed information. Also note that if the GPS screen has a backlight, using it will reduce the battery life so it is best not to use it.
6. Digital Mapping – A basic hiking GPS does not provide any digital mapping, just an accurate grid reference to use with your paper topographical map. Digital mapping displays map details on the display screen of your GPS device. Digital mapping may be either built-in topographical and base maps, or complete OS (Ordnance Survey) maps. Basic built-in topographical and base mapping usually does not show contour details, simply a location between general features like roads and is insufficient for hills and mountains navigation. Some GPS devices enable you to buy costly detailed topographical maps but they are not as detailed as OS mapping. However, before buying a more costly OS mapping GPS decide if you need this feature or not.Although OS mapping is beneficial on complex terrain, it is not so important on trails where there are many prominent features to aid navigation. Also be aware that OS mapping may be difficult to view on small display screens and reduces battery life as it consumes more power. Before selecting your GPS device consider the standard maps included in the purchase together with the cost of additional maps if available.
7. Digital Mapping Software – Digital mapping software enables the planning and record of your hiking routes much easier. The basic functions of this type of software are: viewing maps on your computer and downloading them to your GPS unit; and uploading hiking routes you record whilst hiking from your GPS to your computer for storage, review and editing. There are a number of other features that may be available including: gradient profiles; hike time estimates; printing maps; route card printing; 3D/aerial views; 3D virtual fly-through of routes; search OS map by feature or place name. When selecting a GPS device with mapping software, a good one should enable you to store 20 hiking routes or more and be able to store 500 waypoints or more.
8. Memory Capacity – Some hiking GPS units have a slot for a memory card to store extra mapping data whilst others have just a built-in memory. Ensure any built-in memory is a sufficient capacity to record waypoint data for several hiking routes at any one time, particularly if you are going on a multi-day hiking or backpacking trip. A memory capacity of 20 MB is usually adequate for a mapping GPS device.
9. Instrumentation – A compass and altimeter are the two most common instruments provided on a GPS for hiking:
- Compass – There are generally two types of compass: a standard GPS compass and an electronic GPS compass. A standard GPS compass records and monitors co-ordinates of where you have been and where you are going. The calculations your direction of travel but can only do so if you have a GPS Fix and are already on the move. An electronic compass functions like a traditional magnetic compass and most need to be held horizontal, still and pointed in the travel direction. If your GPS device does not have an electronic compass it cannot give you a direction reading unless you are moving for a short distance. Electronic compasses use battery power and reduce the life of the battery so you may want to switch it off to conserve power if allowed. Many hikers do not see the need for a GPS compass as they carry a magnetic compass that does not need batteries.
- Altimeter – Altimeters come in three types: standard GPS altimeter; barometric altimeter; and combined altimeter. GPS altimeters are often based on data from satellites and may be up to 50 to 100 feet inaccurate. Barometric altimeters are barometers which provide height readings and changes in pressure when ascending and descending and are more accurate. They can also be used to forecast changes in the weather conditions. A combined altimeter uses both of the previous two methods to provide a combined altitude reading. Also, the barometric altimeter serves as a default reading when no GPS signal is available.
10. Mapping Compatibility – Uploading and downloading waypoints for hiking routes using mapping software is essential for frequent hikers because the manual entering of waypoint data is too slow. It is therefore essential that the GPS device, digital mapping software and computer are compatible with one another.
11. Mapping Updates – The capability to update both the GPS device software and maps, both easily and at a reasonable price, is also an important criteria to think about when selecting a GPS device.
When selecting a hiking GPS, the main thing to decide is whether you only want an entry-level device to provide you with a map grid reference to use with paper maps and a compass to determine your position. Entry-level devices are cheaper and have a longer battery life but their storage capacity for waypoints and routes is usually limited. If you want to be able to do all your navigation with a GPS device then you need one that has mapping functionality. You can then decide if you want a colour or gray-scale display; a compass and/or altimeter; or expandable memory slots for extra maps, waypoints or routes; etc.