In order to begin this puzzle, you will have had to complete The Su Doku Challenge, Part 1 and collected a copy of the new grid from there. Otherwise, the method is exactly the same; though the grid and the terrain are significantly harder. It should be especially interesting for the mountain bikers among you.
Su Doku was first devised by Howard Garnes, an architect from Indianapolis for Dell Magazines, who published it under the name Number Place in their magazine, Math Puzzles and Logic Problems in 1979.
It was taken up in Japan by the Nikoli company, in their magazine Monthly Nikolist. They used the title Sunji wa dokushin ni kagiru, which tranlates to 'Number is limited only single'. Not surprisingly, the name was soon shortened to Su Doku, meaning number single.
In 1986 Nikoli introduced two rules for the grids: that they should be rotationally symetrical through 180 degrees and that the maximum number of filled in squares should be 30.
Next in the Su Doku story is New Zealander Wayne Gould. He was working as a judge in Hong Kong and was looking for something to do in his retirement - once the colony was handed back to China in 1997. He had picked up some Su Doku on a trip to Japan and decided to use his amateur programming skills to write a program to generate Su Doku grids.
The craze for Su Doku didn't start however, until the London Times started publishing Gould's grids in November 2004 and the rest as they say, is history.
(Sources: Stuck on You by Ivan Semeniuk in New Scientist No:2531/2 and How to Solve Su Doku by Robin Wilson.)
NOTE: It has become clear that the grid for this cache has two solutions. Both solutions work equally well, so there is no reason amend this puzzle.
Please use some discretion when making your log. Making things too obvious will spoil other people's hunt.
You can check your answers for this puzzle on Geochecker.com.