## Sampling for Tree FormIt doesn’t matter how the taper equation was computed, or what equation was used. No matter how the trees were chosen to build a volume table or taper equation, the
trees Some modern systems use a "third diameter" to fine-tune the determination for
taper. That really helps, but in the end there is always the question of how good the
answer is for the specific inventory
The Relascope is a good instrument for this purpose. Choose a point where you can see the tree well. A good Relascope scale for this is the "wide angle" scale, and you might consider purchasing this scale the next time you buy a Relascope. You can also use any other scale, since the band widths are all equivalent to certain "percents" of the distance to the tree. It is particularly handy to use bands that are the same width, and perhaps the small equal-sized bands would be a convenient choice in most cases. Rather than trying to read the diameters at different heights, you can measure the distance between points where the tree exactly fits the Relascope bands. The stems of real trees are surprisingly "bumpy," especially around branch whorls. You may find that you need to pick a point after looking up and down the stem several feet in each direction and perhaps ignoring the branch swellings. A staff to steady the Relascope will come in very handy. With this technique, you can at least check the gross volume (outside bark) against the taper equations or volume tables that you normally use. If the measurements are very close, then so much the better. If there are differences, you have some idea how large they are. The trees should be chosen randomly or systematically from actual cruise trees, if possible. Many years ago, Lew Grosenbaugh developed a technique called "height accumulation" which used this "bar matching" technique, along with a simple way to manipulate the readings quickly on a 2 register adding machine. Those days are long gone, and a programmable calculator or field recorder application will do this work far better. The concern with taper or volume determination, however, is just as pertinent as when
Grosenbaugh first worked out his system. The solution is the same. Measure some trees and
get the answer directly. The only way to eliminate a whole set of assumptions and possible
errors will If some of you do this at regular intervals (or use some other instrument) and have any practical advice for our readers then please e-mail us with your suggestions or observations.
http://members.aon.at/fob/ They also have a very extensive set of publications on the Relascope and research into Variable Plot Sampling (Angle Count Sampling is their term). If you need a Relascope manual, or are interested in their technical publications, write to them at: FOB |

*Originally published July 1998*