Measuring Height Two Ways

I decided it would be neat if I were to use similar triangles to find the height of the pole. I used a tape measure to measure out 20 feet from the pole and put a marker there. Then I took a picture with my phone.  I uploaded 2 copies of the picture to GSP and made two triangles.

They are both similar but have different scales; one is real world, and the other is on GSP. GSP gave me the lengths of the triangle in centimeters, so then all I did was set up a proportion to get the length of the pole. I also had a second way to do this: I set up a tangent equation to find the pole. Both results were very close but i think that the tangent equation is more accurate. (~TR1)