Heatmap
There are no years with heat yet.
For any application that takes a tile layer as a URL. The address holds the key, so whoever has it sees the heatmap.
One layer eachThrows every heat tile away and adds back every day that is processed with its latest data; the others go in as they are rebuilt. Needed when the tiles look wrong, or to show nothing old while every day is rebuilt. Changing the Heatmapper's settings does it by itself.
The colour is the way travelled: red is north, green east, cyan south, purple west. Grey means both ways alike; brighter means more often.