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Maybe is not the perfect stackexchange site to ask this but I try. Feel free to move or close my question, but, if you can, suggest me where I can ask this one:
I took a photo with a compact digital camera and EXIF says that focal length is 6.2mm (and equivalent focal length of 35mm = 38mm ). My subject is about 14kms away and it takes up almost the entire height of the picture of 2560 x 1664.
How can I calculate the height of my subject? I do not ask the highest precision but a tolerance of +/- 10%.
This is the photo: Etna I want to know the volcano's smoke height.