To determine the correct
two-letter 100,000-meter
square identifier, look at the
grid reference box in the
margin of the map. You
must look to see where the
00 lines falls in reference to
your point on the map and
use the identifier that is on
the same side of the 00 line.
With this example, your
point is below the 00 grid line
so the 100,000-meter
square identifier is UP.