Re: [Talk-ca] Canvec forest redux

[Paul Ramsey]

On Thu, Sep 29, 2016 at 5:58 PM, Adam Martin 
wrote:
>
> You know, it suddenly strikes me that part of the reason that there is so
> much trouble with the forest polygons from the Canvec data is less the
> accuracy of the data and more the fact that it is brutally difficult to
> work with.
>

This is my complaint about the forests. It's not just the fact they are
loaded as complex features, it's that even the simple polygons are just
packed full of vertices. So modifying them requires 5x the work of
modifying other things. They're only partially loaded into OSM and unlikely
to be updated. If there was ever a feature that a human-mediated map like
OSM should skip, it's this kind of landcover stuff: if one needs a
landcover in ones map, get a computer to do a classification of landsat 8,
and load that into your map, it'll be better in a global sense than the
handballed thing, and far more up to date than hand-massaged forest
polygons that were captured in the mid-80s.

P.




> These enormous multipolygon relations, linking the forests to open areas,
> wet lands, and water polygons, creating inner and outer relationships all
> within the confines of the Natural Resources map divisions. I wonder would
> these be nearly as hard to work with if the multpolygon relation itself
> didn't exist? I understand the reasoning for relations themselves - they
> are core mapping elements meant to describe logical arrangements between
> items. Bus routes are one of the prime examples of such a thing. Has anyone
> leaned back and just considered that, in the case of this forest data, we
> might be going a bit far to have inner and outer boundaries to describe
> breaks in the tree line? Think of it this way, what is the use of a
> multipolygon relation? In the Wiki, it is used to create an area for which
> the boundary is defined by multiple ways and / or an area possessing holes.
> When we import a forest multipolygon, what are we trying to describe
> exactly? An area of forest  with holes ... which are not holes, but are
> simply areas when the tree line breaks and another feature is present (open
> grassy area, a lake, a marsh, etc. Looking over some of these polygons, it
> is notable that houses or owned are often not provided a gap if they are
> not in a city centre. Even more unnerving is the fact that roads, major or
> minor, are also not provided gaps nor are they part of the relation.
> Essentially, the most important human feature of an area - the
> transportation network, is not important enough to be part of the relation.
>
> Perhaps it would be better to eliminate the multipolygon itself? Simply
> map the forest areas and open areas and lakes and so forth and add them to
> logical relations afterwards. Take my home province of Newfoundland. If one
> were to build a forest polygon, it could be logically broken down into
> regional multipolygons (such as one for the Avalon Penninsula). Or it could
> even be further divided based on localized geometry.
>
> Just some thoughts on the matter.
>
> Adam
>
> On Thu, Sep 29, 2016 at 6:26 PM, Sam Dyck  wrote:
>
>> Hi everyone
>>
>> Sorry for bringing this up, but I need to some Canvec importing. Given
>> the controversy about Canvec earlier this month, I'm trying to decide how
>> to do this. I could:
>>
>> - Leave the forests out entirely.
>> - Or use it as an opportunity to experiment with the Manitoba Lands
>> Initiative forest data. We've discussed MLI before and done some limited
>> importing. And I'm curious to take a look at the data.
>>
>> Thoughts?
>>
>> Sam
>>
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[Talk-ca] Canvec forest redux

[Sam Dyck]

Hi everyone

Sorry for bringing this up, but I need to some Canvec importing. Given the
controversy about Canvec earlier this month, I'm trying to decide how to do
this. I could:

- Leave the forests out entirely.
- Or use it as an opportunity to experiment with the Manitoba Lands
Initiative forest data. We've discussed MLI before and done some limited
importing. And I'm curious to take a look at the data.

Thoughts?

Sam
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