[Talk-ca] [Imports] Ottawa, Canada Tree Import

James james2432 at gmail.com
Thu Jun 29 11:07:32 UTC 2017

This is probably why dbh is used as the diameter only changes a tiny
fraction of the circumferance per year, so the data is less stale and you
dont have to audit them every year

On Jun 28, 2017 9:21 PM, "Max Erickson" <maxerickson at gmail.com> wrote:

> On Jun 28, 2017 6:46 PM, "Kyle Nuttall" <Kyle.Nuttall at hotmail.ca> wrote:
> The biggest issue to resolve is tagging the thickness of the trees. The
> data was provided as the diameter measured in centimeters. I understand
> that the circumference tag was made for ease of use, but anyone that is
> collecting data specifically for trees would know the concept of Diameter
> at Breast Height. It's my belief that the more the data is manipulated, the
> more errors that are introduced. If converting a DBH of 9cm to
> circumference in meters, you get 0.2827433388230814...m. How many digits
> is sufficient for accuracy? I suppose 0.001m would as much as needed.
> A sensible conversion shouldn't imply such a precise result. Round
> instead. Not quite following the rules for significant figures, a 9 cm dbh
> becomes a 0.28 m circumference ( which round trips back to 9 cm using the
> same vaguely sloppy method).
> On the other hand, given the morphology of trees and wide use of dbh in
> biology, I think it makes sense to use it. In taginfo, centimeter seems to
> be the more used unit. Explicit units in the value, like dbh=9 cm makes
> more sense to me than putting the unit in the tag (which invites nonsense
> like divergent values).
> Overall, I sort of question the value of putting the stem size in osm.
> Mostly because the data is fairly likely to go stale as the trees grow (so
> anyone who really cares for it is best off going to the source).
> Max
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