Measuring tree height from a photo is accomplished by having a photo of the tree with an object in the image of known measurement to provide scale. Then measuring the image of the tree and the image of the scale object in the photo and computing the height as follows.
Note the following from the photo using a ruler (a ruler in inches and tenths simplifies calculations):
measurement of the scale object on photo with the ruler
measurement of the tree on photo with the ruler = T
actual measurement of the scale object = Sm (this is the measurement recorded at the time of the taking of the photo)
Compute the height as follows:
T ÷ S x Sm (measurement) = estimated tree height
In the illustration the actual measurement of the scale is 4 feet
T = 5.57
S = 0.55
Sm = 4 feet
5.57 ÷ 0.55 x 4 = 40.5 feet
Measuring the spread of the crown can be accomplished with the same method by substituting Sp (spread) for T in the above formula.