Measure the length of the shadow, and record the time. Look up what
the height of the sun was at that pouint in time from tables, and use
geometry.


The original poster didn't indicate he could get to the tower, but if he
could, there's a better way than above that doesn't require "tables".
..... simply measure the length of the tower's shadow. Then with a
yardstick, or equivilent, measure the length of the vertical yardsitck's
shadow. You now know the height and shadow length of the yardstick. You
also know the shadow length of the tower. The two are proportional.

The height of the yardstick divided by the length of its shadow is equal
to the height of the tower divided by the length of its shadow. A simple
algebraic expression ... easy to solve for the height of the tower.


Ed K7AAT