This is a photo of the top of a historical stone post, known as a ‘staddle stone‘. Staddle stones were used to build barns off the ground, in order to protect them from rodents and water.
In this picture there is a beautiful example of some sun-loving golden Xanthoria lichens enjoying the south side and the moisture-needing moss thriving on the north side of the stone dome.
The split between the two isn’t perfect, Xanthoria can survive in partial-sun and mosses can survive in direct sun if it’s damp enough, but look closely and you’ll see how the colour compass works.
South is at the bottom and it is hear that we find the most brilliant golden coloured lichen. Xanthoria turns a muted yellow/green/grey colour if it isn’t in full sun.
For more on navigating using lichens see these books.
You might also enjoy:
The Beginner’s Guide to Natural Navigation – Online Course