This is a Reverse Wherigo Cache. There is no cache at this spot, so don’t go there. Furthermore, if you do go there, there’s a FasTrak/TheTollRoads fee that will be a waste of money. You must solve the puzzle below to obtain the information required to find the geocache.
Oak in Fork (Irvine Regional Park)
This is a "Reverse Wherigo". The Reverse Wherigo cartridge can be downloaded for free here: Wherigo. More details about Wherigo are between the "***" below.
To solve the Reverse Wherigo cache, first, solve this Sudoku:

Next, starting from the top left and working down to the bottom right, enter the numbers corresponding to the shapes into the table below. Finally, enter those three six-digit numbers into Certitude to verify that you got it right, or simply risk it - your choice. Finally, place the three six-digit numbers into the Reverse Wherigo cartridge and find the cache.

You can validate your puzzle solution with
certitude.
*** This Wherigo converts your player into a virtual version of the "Reverse Cache Box" which tells you the distance to the cache, but not the bearing. You may begin your search from anywhere in the world using your smartphone or a Wherigo-compatible GPS to navigate to the cache. The cartridge was created by -Waldmeister- and is available to download from the wherigo.com website. -Waldmeister-'s "The first Reverse Cache [WIG], GC357G1" is the original cache in this family.
Your task is to find the cache by periodically querying your Reverse Cache Box for the distance to the final location. Try to use your Reverse Cache Box as few times as possible. The cartridge contains all the instructions and necessary information to complete it. It is also multilingual.***