[OSM-talk] Parcel data

[andrzej zaborowski]

2009/9/21 Anthony <osm at inbox.org>:
> On Mon, Sep 21, 2009 at 3:09 PM, Apollinaris Schoell <aschoell at gmail.com>
>> problem is how can you convert the weekly updates into osm updates? You
>> can't delete all data and upload again the next week.
>
> I'm not volunteering to do it *weekly*, but I'd only delete and upload (or
> modify) the data that changes, of course :).

Provided each parcel has a unique id in the imported dataset, it
should be possible to automate these updates although there's no
standard way in OSM yet to do automatic updates for imported data,
that I know of.  There is however at least one example of this being
done, for the German localities and there's a smart scheme of tags
that tell the updater which properties should and which shouldn't be
updated.  This prevents the situation where, say, one person comes and
adds a note= tag or the wikipedia= tag to one of the imported objects
and its changeset id changes (or the reviewed=no tag is removed) and
the object never gets updated with official information again.

>
>>> I basically just want the address info.  Having the parcel polygons is a
>>> bonus, but if it proves to be too difficult to maintain I could just move
>>> the data to the ways as an interpolation.
>>
>> just address data seems reasonable. It shouldn't change that much and
>> easier to maintain.
>
> I'll see how much the polygon data has changed since the data I downloaded a
> month ago.  I would think the main changes to the parts that I'm importing
> (not property values and all that stuff) would be when new subdivisions are
> added, which would affect address data as well, and affects the Tiger data
> too.  That and use changes (e.g. residential to commercial), but use changes
> are easy to update automagically and without human intervention.
>
> I could do this as point data.  I could merge the parcel polygons into block
> polygons to cut down on the number of polygons by an order of magnitude or
> so.  It'd be nice to at least see the block lines.  It's great seeing the
> cul-de-sacs and curved corners tracing out the gaps in the roads.
>
> On Mon, Sep 21, 2009 at 3:13 PM, Hillsman, Edward <hillsman at cutr.usf.edu>
> wrote:
>>
>> Hi Anthony,
>>
>> One other possibility would be to calculate and upload parcel centroids
>> (points) instead of whole parcels.
>
> Yep.  Or if I have the patience I could identify the road the address is on
> and put the point a few meters off the road in the center of the lot line
> parallel to the road, this way long lots would look better.
>
> But then, if I'm going to that, I might as well just add the info to the way
> as interpolation data, right?

Yes, but obviously a node in the middle of the parcel, instead of a
few meters off the road is closer to truth and a full polygon is still
closer.  So I'd personally just import the polygons, otherwise someone
will come and draw them manually eventually and they'll be less
correct.

>
> On Mon, Sep 21, 2009 at 3:09 PM, Apollinaris Schoell <aschoell at gmail.com>
> wrote:
>>
>> adding a tag like [hcparcel:verified=no] is useless.
>
> Okay, I won't do that.  :)
>
>> another suggestion. don't make the same mistake as tiger, Massgis, PGS
>> coastline ... imports and tag individual nodes if they are members of a way.
>
> I can't imagine any reason I'd do that.  :)
>
>>
>> don't add too many tags which have no use for osm and can be easily looked
>> up in the source data.

The uses tomorrow will be completely different than the uses you can
imagine today.

Cheers