Geocaching without a GPS

It is possible to go Geocaching without a GPS but rather difficult. We're spoilt with GPS devices telling us which direction to walk and how far we are from a cache, or even view our position on an electronic map.

Before May 2000 the American GPS system used Selective Availability to intentionally add an error of up to 100 meters - I knew first hand about this error because at the time I was writing software to track the position of fishing boats using GPS and Inmarsat-C for communication. Often large fishing boats in harbour would report back to the base station that they were docked 100 meters inland in the car park!

After Selective Availability was removed the GPS position error was reduced to 10 meters. This opened a whole new range of interesting and useful uses for GPS devices, like vehicle satellite navigation and more importantly Geocaching :)

In the photo:

• Compass
• Binoculars
• Ordnance Survey map (Biggin Hill Airport being highlighted)
  
• Zippo lighter
• Montb Blanc pen
• Smiths pocket watch