A GPS ( global positioning system) relies on satellite feedback in order to function, GPS units require unobstructed line of sight. Be aware that signals are often weak in thick forest cover, so you may have to move to a safe open location to obtain a proper signal. They also require movement for the satellite to triangulate and fix your position. In an alpine environment this can be restrictive and may lead to variability in the readings.
Although there is variable cellular coverage in the mountains of New Zealand, it is still worth while carrying a cell phone and, in the case of an accident, trying to use it to call for help. There are recent cases were a mobile phone call has saved people's lives. In an avalanche accident, minutes count and the faster that you can get help the better.
Satellite phones are very good in the hills but still have their drawbacks. They require a clear view of the sky, so avoid gorges or heavy foliage and it may still take some time for a satellite to be in a position to receive your call.
They are very useful for long trips when the opportunity to make regular contact is limited or for professional operations. The weight and cost of the units can be limiting factors for individuals traveling in the backcountry.
PERSONAL LOCATOR BEACONS (PLB'S)
PLB's are small, emergency distress beacons that emit a UHF radio signal when activated. Once activated, the signal is picked up by satellite and/or aircraft and Search and Rescue operations use the signal to ‘find' the beacons, as detailed below.
Carry or purchase only a 406MHz beacon. 406 MHz beacons must be registered with Rescue Coordination Centre of New Zealand (RCCNZ) and it is highly recommended that you use a GPS equipped one.
Note that personal locator beacons must only be used in life threatening situations. If it is a false alarm, get a message to RCCNZ (0508-4RCCNZ, or 0508-472-269) or Police as soon as possible. Once it has been activated, people will be starting to search for you and this may divert SAR resources from genuine emergencies and in doing so may endanger lives.
Like any device that requires a satellite, the Beacons operate best with a clear view of the sky; avoid gorges or heavy foliage. Do not turn the beacon off once you have activated it and stay put.
FOOD, WATER, CLOTHING
As always when venturing into the outdoors remember to bring enough warm clothing, food, and water.