This one is not so much of a matrix as a map.
It’s easy enough to understand. Colours appear on every map I’ve done at least one cache in. The darker the county, the more caches I’ve done there.
Now this is one I’ve definitely been having a go at, to the extent that I completed 15 new counties in 2014. Only 5 counties in England remain for me, and a couple in Wales. I need a few trips to Scotland though, by the looks of it.
And here’s my current one :