[Talk-us] UVM-SAL Buildings

Phil! Gold phil_g at pobox.com
Fri Jun 1 13:07:31 BST 2012

* William Morris <wboykinm at geosprocket.com> [2012-05-31 21:25 -0400]:
> Trying this again, after a hiatus, here is a sample of a few hundred
> buildings from a UVM-SAL land use classification. In this case it's
> for an area just west of D.C. in Montgomery County, MD. I offer it for
> your consideration before I pull the import trigger:
> http://dl.dropbox.com/u/23616645/Geosprocket_Share/mont_b_1.osm

I share the reservations already expressed about the nodiness and
blobbiness of the buildings.  Here's one set of buildings, shown against
Maryland's aerial imagery:


I'm not convinced that a county full of blobs like that will look good on
the map and, thus, whether it would be an improvement over letting mappers
put the buildings in as they get to them.  I'm more comfortable with
things like the building import done a few months ago around Salisbury in
eastern Maryland where the data is much cleaner and, I think, better
serves as a basis for further improvements from local mappers.

I think that this level of accuracy, while reasonably-well-suited to
landcover data, isn't really good enough for buildings.

I'm also over in Baltimore County, so I'd like to hear what other regional
mappers think.

> Some steps I've taken to make it community-friendly include:
> - Removed all buildings that intersected existing OSM features

Definitely an important step.  Thank you.

> - Removed all buildings smaller than 5000 square meters in area, since
> those residential structures weren't being very well-detected anyway

There's not really a good cutoff for this, though.  I saw a couple of
housing developments with blocks of townhouses where random sets of
townhouses were missing.  Presumably the missing ones fell below your
threshold while most of the blocks didn't.  It might be useful to go much
higher and target just the largest buildings (which would also be the more
significant landmarks).  Over all of your data, what does the distribution
of building areas look like?

...computer contrarian of the first order... / http://aperiodic.net/phil/
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