One of the things I came across in my research of how the Vikings went from place to place are sun compasses. Apparently a couple of examples were found in some of the archaeological digs. Here's an image from one of the documentaries I was watching.
I had to try and create one to test out the concept. I selected a small piece of plywood and attached screw in the middle. For the marks I'm just using a sharpie marker. Where I have it at so that I can get to it easily is on my porch railing.
Here's after a few hours. While I'm not trying to mark it very precisely I'm able to get what north is in general. Where the red line is the closest to the screw would be the place it intersects with the north south axis. You'd simply draw a long line from that place through the screw. From then on you'd have a compass of a sort to use. You'd also have to make them several times per year depending on how long your voyages happened to take.
Quite a fascinating bit of technology and history.