trtl.nodes.pub keeps track of public TurtleCoin nodes. It polls each node every ~10 minutes.
trtl.nodes.pub updates its list from github.com/turtlecoin/turtlecoin-nodes-json.
Each dot in the poll history column referes to an attempt to poll the node for info. If the poll was succesfull, you see a full dot, if not, an empty dot. Dots on the left are older than dots on the right.
Based on the poll history, nodes.pub calcluates a score. The newest poll results have more weiht than the older ones.