First off watch the Youtube video at http://youtu.be/n9s8FUG2S64. This sets the problem up. This is a basic orienteering problem.
This works better with students if you take them out in a bus to actually collect their own data. When I have done this problem with students. I ask them to guess the distance between the two towers and have them plot that guess on a number line with sticky notes. Then I break them into teams and tell them that whoever is closest to the actual answer both by guess, measurement, and mathematical proof wins a candy bar of their choice.
DO NOT CHECK THE TWO BOXES. THIS WILL REVEAL THE ANSWER!! TRY TO MODEL THE PROBLEM ON YOUR OWN FIRST!!!

Once you have a model check and see if your model matches mine. Then click on the box that reveals the actual answer based on a google earth image. Notice the difference between my youtube model and the actual answer. This is what will happen with all student work. Some measurements will be so far off that their answer will not make sense. Be prepared for this. The only way to combat this is to tell them to be careful when measuring and have several student take measurements. "Measure twice. Cut once!" The fact that we are eyeballing the measurement makes it a gross estimation. Any kids in the military will show you their angle measurement system. It is much more accurate:)