Hi Mark,

as i looked at the cache-description, i saw an english translation. Check up this again.
The description says, you can log this cache, when you have a garmin-device, which can use the EGNOS data from the european satellites. You only have to log with a pic, which will show your garmin using EGNOS (the D's in the strength-bars).
Hope, i've helped you out.

cheers, Thomas