I echo the sentiments of the others. Outstanding report! Chalk up another for the Pennsylvania team. You all in the Keystone State are so far ahead of the rest of us in terms of the number of sites you've measured that you could take a year-long vacation from measuring and still remain ahead of us all-so-rans.
In terms of judging tree height in the field, it is both an art and a science, but with the emphasis on art. There are many factors that enter the picture including tree shape and even tree color to an extent. Certainly the proximity of nearby objects to use for scaling is helpful, but even when objects are present, big errors can be made - by experienced people. Your post has inspired me to write an essay on the physical and psychological aspects of judging tree size. We in ENTS have plenty to say on the topic, if anyone does. As an example, I just communicated with a retired forester from Virginia who had been measuring and dating downed trees on the Montpelier Estate north of Charlottesville, VA. The best he could get for a prostrate tuliptree was 135 feet. Of course it was broken up, but he had attempted to reconstruct it. Gaines McMartin explains that you can't reconstruct the original heights of fallen tuliptrees, so the poor fellow was doomed to fall short, I guess. But he didn't express awareness of the magnitude of the challenge in our conversation. However, this is not a criticism. The fellow is highly knowledgeable about the tree species in the area, where they grow best, etc. I could tell that he has extensive knowledge of the trees in the area and he is personable and easy to talk to. However, I doubt that he believed the heights I was measuring for the tulips on Montpelier are even possible. He has no experience with lasers, and is well aware of the challenge of measuring broad-crowned hardwoods on sloping ground and in close proximity to one another. He doesn't even try, which speaks well for him.
If forestry professionals with decades of experience can't accurately estimate tree height under forest conditions, then it must be a more highly specialized skill than we have realized. The forester walked by at least 15 standing tulips in the area over 150 feet in height and easily that many between 140 and 150 and he missed recognizing their exceptional stature - every last tree. So, it is time that we in ENTS turn our attention to the task of describing our estimating skills to others, which means we have to figure out what it is that we do. BTW, folks like Will Blozan often estimate tree height to within a foot. I'm always impressed with Will's eye What does Will see? What is he using for comparison purposes? I'm pretty good, but not that good. I'll recognize a new candidate for the 150 Club in Mohawk, but I can misjudge by as much as 10 feet, sometimes more. I won't misjudge by 30 feet, which routinely happens for folks without an practiced eye. Sometimes they miss by 50 or 60 feet.
Well, enough on the subject at this point. Stay tuned. Again, thanks for the excellent post. And a big salute to the Pennsylvania team.
Robert T. Leverett
Co-founder and Executive Director
Native Native Tree Society
Co-founder and President
Friends of Mohawk Trail State Forest