3 ms·

Hmm, how about sketching the pattern of stars you see on the horizon along with a date and (approximate) time?

• icebraining 15y ago
  Or learn how to build and use an astrolabe. It's not rocket science and gives them your approximate latitude.
  • ruggeri 15y ago
    Good point. If the island has WiFi you can look it up on Wikipedia :-)
    • icebraining 15y ago
      I learned how to build one in elementary school (as a Portuguese, we have quite an history of sea exploration).