Posted: Sat Jul 08, 2017 10:23 pm
by Don
The displacement theory...a rather empirical approach, also occurred to me, long enough to muse how much water it would take, how much of a container it would take, role of evaporation, and other such considerations. But ultimately, at a certain scale the impracticality easily outweighed the data yielded. But for tropical fig species, I have not thought of any better method...

In our assigned roles in American Forests' (AF) Measuring Guidelines Working Group (MGWG), we considered such things...your musings are not far off the mark. For one, there is a technique variously known as "Cloud Mapping", where digital images are taken around the tree (much as you suggested), and entered into a software that creates a surface map of the images taken...very complex math and computer programs yields the surface map as well as mathematic relationships such as circumference, volume, and a high degree of accuracy.

Another technique, even more complex, perhaps is known as Structure from Motion, where aerial (plane, drone, and at larger scale, satellite) video data informs SfM software and provides a more forest-level manner of measurement.

While not known as I was at the University in the 70's and 80's, tree heights became ascertainable from remote sensing techniques known as LIDaR, where radar signals are sent out in known frequencies and such, and then their reflection received...the manner and amount of those signals received can be used surprisingly effectively in measuring tree heights, with sufficient funding, at the forest level. We have members in NTS who actively seek such LIDaR coverage, using it to filter their forests in their search for big trees.

Most recently, a member of the AF's national big tree Certification Cadre mentioned research he'd been a part of that used hand-held digital cameras, to estimate crown dimensions.

We do have research citations that provide solutions for estimating equivalent girth of highly buttressed species, but they are at best estimations.

So yes, your question was apt, and your thinking not that far off the mark! Tell us about yourself !!