Solution: Ask a person to to stand beside the flagpole, take a picture. Then measure the the height of the person and the flagpole in the picture and then you can find out the scale ratio by the the real height of the person and the height o the person int he image. Using that ratio you can find out the height of the flagpole.
Image (object) Image (pole) Real (object) Real (pole)
1.4cm 4.6cm 1.75m 5.75m
1.8cm 6.15cm 1.565m 5.35m
2.1cm 6.4cm 1.8m 5.48m