Now that storage and processing power are cheap and plentiful, there are a range of options for navigation 1) using visual keypoints ala https://scape.io https

Now that storage and processing power are cheap and plentiful, there are a range of options for navigation 1) using visual keypoints ala https://scape.io https://scape.io 2) a much older idea, used in cruse missiles: radar contour mapping. 3) decca or loran 3.5) passive radar 4) inertial dead reckoning(sensors are much, much better nowadays). 5) laser painting way points. 6) multi spectral, multi viewpoint cameras with slam/visual odometery (with a database of coast lines for pinpointing land fall.) or better yet, a combo of all of them. The more data points the better.