[Imports] Ottawa, Canada Tree Import

Max Erickson maxerickson at gmail.com
Thu Jun 29 01:19:14 UTC 2017


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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