I have a dated dumpy level that I would like to add something to in order to measure the angle of elevation of buildings, trees and other objects. It doesn't have to be exactly perfect and doesn't need to be expensive. Any advise will be appreciated.

If you could mount it on something that allows you to adjust it until it shows level, then all you'd really need is a plastic protractor, a string and something like a pencil. You could set up the level so it points at the base of the thing you want to measure and it shows level. Do this by sighting down it at the objects base. At the other end from you eye, hold the pencil up until you eye (from the same spot as before) sees the top of the object at the pencil point. You might want to wrap some double stick tape around the pencil and stick it to the end of the level after you figure out where it needs to be. Then, run the string from where your eye was to the top of the pencil. Take the protractor and measure the angle between the top of the level and the string.