On Tue, Nov 13, 2018 at 10:09 AM Sergio Manzi <s...@smz.it> wrote: > Yeah, agreed. And I think in our context "*estimate*" should be more > taken as "*quesstimate*", i.e. "*a first rough approximation pending a > more accurate estimate, or it may be an educated guess at something for > which no better information will become available*" [1]. > > Now... how do we tag this... "*thing*"? :-) > > My personal idea is that it should be: > > *either* > > *measure*:accuracy=estimate (e.g.: height=10 + "height:accuracy=estimate") > > *or* > > accuracy:*measure*=estimate (e.g.: height=10 + "accuracy:height=estimate") > > *and* > > get rid of all the est_* tags (e.g.: est_height=10) > > I'd mostly agree. When this gets wikified, let's make it clear, though, that the ruleis "map what you know" rather than "don't map until you have all the detail." (Too many discussions here come up with schemes where mappers have to do additional research beyond what they can see in the field before they can map in a conformant way. We don't want that.)
Now, as to the height of a tree. I've been tempted to map a few locally spectacular examples, particularly of _Tsuga canadensis_ (and decided to refrain: https://8thlnt.wordpress.com/). I had been thinking in terms of just putting in the number of metres - but if I were to map such a thing, ought I to distinguish: - step back and simply visually estimate how many copies of my six-foot hiking partner it would take to make the height of the tree. - pace back a known distance (with the usual inaccuracy of pacing off a distance) and use a clinometer to measure the angle subtended by the tree. - frame the tree with stadia marks in a transit and tape off the distance to the tree - (I've never done this!) Climb the tree and drop a weighted tape. The accuracy of these techniques varies by 4-5 orders of magnitude. The simple visual method is probably going to have a standard error of a few metres on a big tree (because I'm reasonably skilled at such things), which can be reduced to tens of cm with the clinometer, a few cm with a transit and tape, and sub-cm using direct measurement with a tape. With the specific example of a tree, nobody cares about a few cm, because trees flex, and grow, and measurements aren't going to be repeatable to that level (With a tower, it might become significant.) At that point, for a tree, the only significant difference becomes "are measurement errors of the same order of magnitude as the natural variation in the measured quantity?" With a visual estimate, the answer is most likely "no", with a clinometer and pace count, it becomes "yes," and everything more sophisticated is mostly "wasted precision". So for a tree, "measured" and "estimated" really are the only two categories that matter. (And perhaps the date of the measurement. Trees grow, and the big ones all eventually take storm damage and die back.)
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