2 ms·

1. Use a string 2. Get a second globe

• psychoslave 2y ago
  For 2, a small mirror can do the trick too.
• asadotzler 2y ago
  In a former life and trade, I used straight edged rulers to measure effectively on convex surfaces by simply tilting the edge forward rounding the convex surface, riding it along until I hit my mark and reading the value.