[Talk-us] parcel data in OSM

[Greg Troxel]

Serge Wroclawski <emacsen at gmail.com> writes:

> On Fri, Dec 28, 2012 at 5:25 PM, Brian May <bmay at mapwise.com> wrote:
>
>> And as Phil said, sometimes it doesn't make sense to follow the
>> parcel lines exactly, such as if the parcel boundary extends into a
>> road and it makes more sense to draw the boundary where the park area
>> appears to end some distance from the road.

That's a good point in the general case.  In Mass, parcels stop outside
the road and the roads are their own parcels.  So for a conservation
area, the legally protected area is exactly the parcel.

> So it sounds like what you folks would want is for data where it's
> available, some sort of tracing background layer, or else a per object
> import where you could load the data in your editor of choice and
> manually select how they go in?
>
> That seems both doable and non-controversial.

I think what Jason was suggesting was looking at a small number of
individual parcel polygons, and then, based on local knowledge, deciding
to add them to OSM with appropriate tags.

As an example, I've done this for two conservation properties in my
town.  I knew which parcels they were, in one case because I had already
hiked it and mapped the tails, and in another because I belong to the
group that bought them and had seen maps (from massgis data) showing
which parcels were being acquired.  So I found them from the assessor's
parcel database (massgis, usual PD-attribution-requested), and copied
them, adding tags.  This is totally different from adding all parcels.

With respect to Jason's suggestion that there's a causal link between
the open-space layer being imported and people mapping trails, I think
it's as strong as the theory that says imports discourage new
contributors :-) By that I mean that I don't really believe either
theory, but it's interesting fodder for discussions.  In my case, his
suggestion of a link rings true for me; I became interested in OSM when
a friend pointed out that there was already road data and the open space
layer in Mass.  But to answer the real underlying question, one has to
analyze the ensemble of all people who might map, and that's a different
and much harder question.

My own take on which parcels to import are to do it by hand only, but if
one is adding a landuse tag for an area that logically should line up
with a parcel boundary, it makes sense to use the best representation of
the parcel.  So that includes formal conservation areas, but also
forestry plots and anything else where a landuse tag boundary is
logically associated with parcel boundaries.   It's really not possible
to find out the boundaries by seeing anything in the woods, and hiring a
surveyor to stake them out and then measure the corners is expensive
(and probably not doable, on other's land).

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