[Imports] Ottawa, Canada Tree Import

[Rory McCann]

On 27/06/17 22:11, Kyle Nuttall wrote:
>>* dbh is an undocumented tag
> 
> My only argument against this is that DBH is a very commonly used 
> measurement in botany.
> 
> And with the nature of how the conversion to circumference would work 
> (Pi being an irrational number), how many decimal places would be 
> necessary and/or too much?

Like many techies here, I didn't know much about botany, but yes, "dbh" 
does seem to be a word. Wiktionary[1] has it. Perhaps write a page on 
the OSM wiki explaining the tag in case people stumble upon it. However 
you're using "centimetres" as the unit, Is that the best unit? Maybe 
metres? Your example has `dbh=6`, maybe `dbh=0.06` would fit better with 
the rest of OSM. You could add the unit as text to make it clear: 
(`dbh=6cm` or `dbh=0.06m`), or a new tag `dbh_cm=6`?

Have you looked at these values to see if they're OK? The Belfast trees 
dataset has some trees recorded as hundreds of metres high, clearly 
nonsense. There aren't many dbh-ish tags in OSM now[2], mostly 
`dc-gis:DBH`, but 91% of them have a value of `99`, not very useful! 
What's your dataset like? Just make some simple graphs to look at it.

And yes, you should check if the trees you have intersect with exiting 
OSM data, like buildings.

You should also check if/how many trees are really really close to 
existing OSM objects, like roads. If there's a tree you have that's 1cm 
from a motorway line in OSM, then *something* is wrong. (could be the 
tree, could be the motorway in OSM, could be both)

Have you ran this by the local community? What's the feedback there?

And I don't see a problem with external IDs in OSM :). Though you could 
placate some by changing to a new tag (maybe `city_of_ottawa:ref`?)


-- 

Rory


[1] https://en.wiktionary.org/wiki/dbh
[2] https://taginfo.openstreetmap.org//search?q=dbh
[3] https://taginfo.openstreetmap.org/keys/dc-gis%3ADBH#values