estimating height at different distances

A recent sighting report gives us a chance to theorize different sighting elemnets...."Elementary my good Watson!" If at the distance of 250meters away can a sightee judge between 8ft,9ft,10 in height?For the sake of argument lets say that people outside the US that use the metric system often use meters to judge what we use as feet.Even then could they judge height acurately or even closely? I know tall is tall and Bigfoot creatures are allegedly TALL.I'm thinking more observation experiments will be done this fall.Its state fair time nowwwwwwwwwwwwwwwwwwwwwwwwww! and have a nice day! :)