Automatic Anchor Mark. This is what it does. If the following are ALL true:
Then, OpenCPN will drop a waypoint at the current location, with the name - “Anchorage created on [Date Stamp]”.
Thus waypoints are automatically created for known good anchorages as you shut down the computer. The 0.25 NM condition prevents clogging up frequently visited anchorages with closely spaced waypoints. The other conditions help to prevent spurious waypoints.
To use this feature find opencpn.conf or opencpn.ini as it is called in windows. Search for a line like this:
AutoAnchorDrop=0
and change the value from “0” to “1”.
Also see Configuration File