I'm standing on the roof of my building with nothing but a laser range-finder, and I want to know the height of my neighbor's home. Who can tell me how to do it with the least number of laser measures?
The range-finder only tells me the distance to things in a straight line.
Some ascii art for illustration:
O <- Me
-|-
_______/_\_
| |
| | ___________
| | | | \
| | | | }
| | | | } measure this
| | | | }
_| |_________| | /