On your bike whereigo geoart is located near blanchetown, the series should not take you too long but may do if you do every wherigo properly.
The cache is NOT at the posted coordinates. Trust us.
In order to find this Reverse Cache you need to download a Wherigo cartridge made by -Waldmeister-
It is located here.
After starting it you will have to type in these three numbers when asked:
813233
252543
396659
Every time you ask it, the cartridge will tell you your distance from the cache, but not the direction.
Based on this information you should eventually be able to deduce the final location.
Once you get within about 20 metres from the cache, the cartridge will give you exact coordinates.