When the United States global positioning system was thrown open to public use in 2000, few guessed it would unleash a treasure-hunting phenomenon now taking hold in New Zealand.
Dozens of GPS-equipped Kiwis are traversing the countryside taking part in an activity called geocaching - uncovering hidden troves with the
help of hand-held devices that allow them to pinpoint any location for which they have the co-ordinates.
The satellite-based GPS was developed by the US military and until 2000 its signals were deliberately scrambled to limit civilian use. Since then, the devices have become standard equipment on boats and many trampers also carry them.
Armed with co-ordinates and clues obtained from a website, geocachers go in search of hiding places - or caches - in cities, the countryside and even underwater.
Depending on terrain and signal strength, a GPS device can take you to within 5m and 50m of a set of co-ordinates.
Retired radiographer and keen tramper Ray Symmans bought his GPS device as a safety measure but soon "caught the geocaching bug".
"There's always the challenge of finding things. But the biggest thing is it takes you to spots that you never otherwise find."
New Zealand has more than 1000 hidden caches; worldwide, there are almost 150,000 in 213 countries.
In the past two years the number of geocachers in Auckland has grown from about six to more than 50.
Geocachers rarely meet and Symmans had been treasure-hunting for a year before a chance meeting with another enthusiast.
On one occasion when another geocacher was sedately zeroing in on a newly placed target on an Auckland volcanic cone, Symmans decided on the direct approach, and headed down the side.
"To speed things up I thought I might fall over and basically slide down the grass, but got a bit out of control and went through a cowpat."
Geocaching is a relatively inexpensive hobby, with second-hand GPS units costing about $100.
Although an affordable toy, they can have serious applications.
Symmans fell and broke his leg last July hiking in the Hakarimata Ranges, north of Hamilton. His GPS device enabled him to provide rescuers with his exact co-ordinates.
He was rescued with 10 minutes of daylight remaining.
