[Imports] UVM-SAL Buildings

William Morris wboykinm at geosprocket.com
Sun Jun 3 15:57:22 BST 2012

The locals and the data have spoken; I'm dropping the building imports
for MD, PA and VT.

My goal here was to rely on automated processes to get the data into
shape, and I fear that even after size filtering, conflation and node
removal the building footprints are mostly not up to the level of
accuracy desired by the community. Too much manual cleanup is still
required for a series of datasets that ultimately comprise over half a
million features. Here's the MD subset, taken as far as I could
without node-by-node adjustment:


It's useful to note that - as land cover - the datasets from UVM-SAL
are of unbelievably high quality. We in the LULC classification world
have been suitably impressed with the object-based results from that
team. However, OSM is a good example of a lingering inflection point
between "GIS" and "Survey" scales. When it comes to building
footprints, the desired quality includes right angles at corners and
ways aligned parallel with walls (such a high bar!). This is a good
distinction for me (and others) to keep in mind for the future as
classification technology improves.

Thanks to all for your input and guidance. I'm heading back to the
drawing board.


P.S. Josh, the conflation plugin hung for me on startup - three tries
using JOSM on Ubuntu 12.04 with 2GB RAM. I'll give it a shot on a
windows box with 8GB RAM later this week.

William Morris
wboykinm at geosprocket.com
Twitter: @vtcraghead

GeoSprocket LLC, Burlington VT

On Fri, Jun 1, 2012 at 12:53 PM, William Morris
<wboykinm at geosprocket.com> wrote:
> Fantastic. I'll give the plugin a run, along with some de-noding (is
> orthogonalization worthwhile in this case?), and check back with folks. And
> here's the pre-filtered buildings file county-wide (in .shp format still):
> http://dl.dropbox.com/u/23616645/Geosprocket_Share/mont_bld_large.zip
> Thanks!
> -B
> On Thursday, May 31, 2012, Josh Doe wrote:
>> On Thu, May 31, 2012 at 9:25 PM, William Morris
>> <wboykinm at geosprocket.com> wrote:
>> > Howdy Folks,
>> >
>> > 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
>> Thanks for sharing. Spatial accuracy is pretty good for an automated
>> process (worst I saw was 5m, usually more like 1 to 2m), though not as
>> good as could be done (very laboriously) by hand given the resolution
>> of the Bing imagery. I'd tend to say this shouldn't be uploaded en
>> masse, but rather somewhat selectively, but I'll let the locals make
>> that call.
>> There a few issues I see which include:
>> * Multipolygons aren't tagged with type=multipolygon, and the
>> building=yes tags should be on the relation, not on the constituent
>> (inner and outer) ways
>> * AREA and PERIMETER should not be included as they can be calculated,
>> and LandCover should not be included unless you can map it to a
>> sensible (preferably already in use) tag, and since it's all 5 I'm
>> guessing that's taken care of by building=yes
>> * Ways are overnoded quite a bit, so run Douglas-Peucker first,
>> experimenting with epsilon between 1m and 2m
>> I've been slowly making improvements to the JOSM conflation plugin,
>> with one goal being to facilitate the conflation of data like this
>> with OSM. If you could provide a version of this file before excluding
>> features which overlap existing OSM features, I'd like to try it out
>> with the plugin to see if it produces useful results. Even better
>> would be if you could take a look at the plugin yourself and suggest
>> what enhancements would make it work for this use case. Note there are
>> a few changes that aren't in the latest JAR available through JOSM.
>> -Josh

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