Our Mental Toolkit

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Our Mental Toolkit

Post by dbhguru » Thu May 09, 2013 1:18 pm


All of us accept the role of instruments in measuring the dimensions of trees. We use laser rangefinders, inclinometers, monoculars, D-tapes, scientific calculators, etc. We employ these instruments following accepted protocols, instructions provided by manufacturers, and our own individual and collective experience.

I would venture to say that In the minds of most tree measurers, instruments are the things. For instance, people use a hypsometer to measure tree height. Presumably, if you follow the manufacturer's guidelines with the instrument, you are guaranteed to get results within some stated accuracy range. Well, sometimes, but often not. We in NTS know this expectation to frequently not be met. We know that instruments have to be used with the right underlying mathematical models to get reliable results. Use of the clinometer to measure tree height is the classic example of an instrument where following the manufacturer's guidelines does not insure an accurate result. It also produces a false sense of security since its purpose is to measure tree height.

If we are to make progress in tree measuring, perhaps we need to rethink our approach to how we describe the tools of our trade. We have our instruments and instructions for their use, but we also have abstract mathematical models that make use of the instruments. For instance, the sine method is used to measure the difference in elevation between two points in space employing a right triangle. We can think of the sine method as a mental instrument or tool. We bring together the mental tool with two physical instruments (laser rangefinder and clinometer) and some rules of the road and we have all we need to measure the height of a point in the structure of a tree above or below eye level to a level accuracy that depends on the accuracies of the individual instruments and their interaction (reinforcement or offset). We can talk about the length of a straight trunk segment of a leaning tree and apply an abstract mathematical tool, the law of cosines, to get the length. We use the laser and clinometer and the law. The instruments supply the lengths of two line segments and the angle in the vertical plane between them. The law of cosines does the rest. A beginner armed with just the instruments would have no way of measuring the segment length without the mathematical model. So, perhaps more focus on the mathematical, i.e. mental, tools is called for. We can find ways to make the descriptions user friendly.

So with this beginning sales pitch, what is our current inventory of mental tools? Do we have them categorized, described, conveniently located in one place? Well, not prior to this point in time, but this will now change. Ed has created a new place in the BBS to put descriptions of our mental tools. Its title is "Dendromorphometry Toolkit". To keep this area of the BBS free of stray, off-the-topic posts, presently, only Ed and I can post to it. We can add others. e.g. Will Blozan and Don Bertollete. However, all of you can be contributors.

For the present, basically, Don Bertolette and I will describe a mathematical tool, e.g. the sine method, in a WORD file with or without attachments. We may get input from the rest of you before finally posting it. Once posted, Ed or I will be the ones to make changes to the basic stand alone tool descriptions. No other kinds of posts will go into the Dendromorphometry Toolkit. Discipline here is absolutely essential. If either Ed or I screw up, the rest of you can apply the Cat-Of-Nine-Tails to our exposed backs.

Don and I will also be working on a composite document that includes the individual tools with possibly other information such as examples of use. In time, this will become the Dendromorphometry Guidebook that I've been promising for years. Don has good ideas on presentation and he has strong connections to other champion tree coordinators and to American Forests. So, he is a logical partner in this redesigned project. To have proceeded in the original direction of producing a book for publication by a major university press was heady stuff - but impractical. Who would read it? Even if we succeeded in getting it published, it would be too narrow for many in the scientific and forestry communities, and it could be seen as a challenge to forest mensuration, which it would not be. But ..... So, a lower profile approach seems advisable, one that challenges recreational tree measurers to learn methods that produce ever greater accuracy and precision.

I emphasize that the individual tools will be accessible to all of you. Some of the tools will be generally described and others more specific to tree measuring. As an example, we have a simple formula that adjusts for head or tripod swivel in measuring the full height of a tree using sine top-sine bottom. But, the formula works to adjust the elevation between two points in space being measured where head or tripod swivel is involved. There is no reason not have the basic formula as a tool in our tool chest and described in terms of what it does more generally, independent of the particular targets. The formula serves for any kind of double sine-based measurement where the centroid of the measuring instrument is moved going from one measurement to the other.

I personally favor this approach rather than to surround each tool with a tree-specific definition. It is the latter approach that is partly responsible for the kind of nonsense in which a tree height measuring method is built into a device, e.g. hypsometer, that only works if the top is vertically over the base - yet the manufacture/distributor doesn't explain the restriction. People then buy the instrument and assume they can: (1) point to the trunk and shoot the distance, (2) point to what they treat as the top and shoot the angle, and (3) rotate the instrument downward to the base and shoot that angle, and trust the result that pops upon the display. They will likely assume that the result is accurate to within the accuracy tolerances of the instrument's laser and tilt sensor. Happens all the time. Even the marketing staff of LTI makes the claim. That is being changed courtesy of input from yours truly.

When Don and I have made a few more passes over the sine method for measuring the elevation of a point, we'll post it. The rest of you can then make criticisms, ask for further clarifications, etc. and we'll return to the drawing board. Tool by tool, we'll post to the BBS topic.


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