This is good method to use when you are on flat, level, ground and you know the distance from where you are standing to the edge of the object whose height you are trying to calculate. This is a good method when you do not know the distance between you and the structure. All you will need to do is take two angle measurements of the structure and measure the distance between the measurements as shown in the diagram below.
Average velocity equals distance over time.
The distance measurement comes from the train of cars. While in the loading station, measure the length of the train. This can be done quickly by measureing from the back of one train car to the back of the adjacent train car. Then multiply this distance by the number of cars in the train. Average velocity equals distance over time.