I just pushed a code update that scrolls the map with the boat, such that the boat is near the edge, and pointed at the center of the map.

Zooming will maintain the boat the same position on the screen.

If you want to test the code, you don't need a Pi, you can run it on any computer (with node.js), and by default it will use OpenStreetmap maps, so you don't need any offline tiles either.

The code is at: https://github.com/pilotniq/piChart