Like matryoshka dolls, you need to work your way to the core of this nested puzzle. From there, you should be able to find the key to decode the cache coordinates:
N 51° [1] . ([6]+[21]) ([7]-[17]) ([4]-[15])
W 000° ([2]+[12]) . ([23]-[10]) ([19]-[9]) ([16]-[14])
Congratulations on the FTF to colincactus.
Puzzle solving hint #4 (more)
In some puzzles, information is concealed in stereograms - often referred to as Magic Eye pictures. If you have two eyes, fairly healthy eyesight, and no neurological conditions which prevent the perception of depth then there's no reason why you shouldn't be able to see the 3D images held within. Like learning to ride a bike, some pick it up immediately, while others have a harder time...
It took me ages! I can't guarantee that this will work for you, but here's my technique:
- First, inspect the repeated pattern of the image and pick out a distinctive feature - something that's easy to spot, such as a light patch on a darker background.
- Identify an adjacent pair of these 'dots' in the pattern, ideally in the centre of the image, but towards the top or bottom. Some puzzles include a pair of dots for this purpose. If you've printed out an image, you can add two clear dots yourself to make this easier. (However, I don't recommend the use of Tipp-Ex on a laptop screen).
- Focus on the image normally, looking at the dots, and then relax your eyes - you're trying to look further away, through the image, not to go cross-eyed.
- As your eyes relax, the two dots will become four. The trick is to adjust your focus until you have just three.
- Keep staring at the centre dot - take plenty of time. Gradually the 3D image should appear in your peripheral vision. Once your eyes are comfortably focussed you should be able to look around and explore the 3D image in more detail.
I know there are online tools that can be used to 'de-construct' these 3D images, but I really recommend having a go - I'd hate you to miss that 'Eureka!' moment.