You need to go to all waypoints to gather information to get to the final location. The waypoints are:
WP0: as published
WP1: S 41° 19.463 E 174° 48.364
WP2: S 41° 19.481 E 174° 48.544
The challenge is that there is no GPS signal reception at all at WP0!
The information you need to gather:
A = Number of light cages along the north wall between WP0 and WP1
B = Number of light cages along the south wall between WP0 and WP1
C = Number of light cages along the north wall between WP0 and WP2
D = Number of light cages along the south wall between WP0 and WP2, less one
E = Number of letters in the four words in parentheses after "Rongotai" at WP1
F = Number of times the word "ONLY" appears on the blue sign you see when looking up from WP2
The last waypoint (WP3) before the final is a concrete structure at an offset from WP0 (in thousandths of a minute, i.e. the 3 decimal places), where:
G = latitude offset = (A+C)*(B+D)-136
H = longitude offset = E*F-178
When you get to WP3, you are nearly there. The old final location is J metres at a true bearing of K degrees from WP3, where:
J = A+B+C+D-E+F*10
K = J*5-1
The cache was a 200 ml sistema containing a logsheet and a huhugrub pebble initially. Please bring your own pen. Stealth is required when finding and replacing the cache. Muggles can appear suddenly, and not always from a direction you expect. Please replace cache exactly where found and cover well.
The current final has been moved by an offset as the old final is no longer accessible. See additional waypoint below. The container has also changed.
Update on 5 October 2010: modified the clues for A to D as a result of the lighting upgrades.
Update on 13 February 2011: modified the clues for E and F as a result of the sign changes.
Update on 18 October 2016: modified the clues for E as a result of site changes.
Update on 28 January 2022: modified the clues for E as a result of site changes.
Update on 30 July 2023: moved final location, see additional waypoints and modified the clues.