Reverse Wherigos converts your Wherigo cartridge into a virtual version of the "Reverse-Cache-Box"
which tells you the distance to the cache, but not the bearing.
The cache page will direct you to load
from The Reverse Cache - beta and enter 3 codes, each consisting of 6 digits. You then have to move around, or use a map, to determine the location of the cache.
This tool will give you the coordinates directly based on the three 6 digit codes.
Note that the code was updated on this page to use the exact code in the Waldmeister cartridge - the coordinates should be exactly the same.
The Decoder and Encoder only work for this one specific Wherigo cartridge - "The Reverse Cache - beta" by -Waldmeister-