[Imports-us] Baltimore Building Outlines Import

Jason Remillard remillard.jason at gmail.com
Sun May 5 01:36:55 UTC 2013

Hi Matthew,

The import proposal looks good! I downloaded the tar file and looked
at the first OSM file.

- There are some duplicate buildings. They were probably added while
you have been processing the data. You may want to proceed anyway and
fix them after if it will be a lot of work redoing the data.
- The osm files are still much too large. The file I checked has
~500,000 elements. The hard limit is 50,000, and in practice you want
to be below that so that you can use the revert plugin. It is too
large run the JOSM validator, which is something that needs to be done
- I did not check for this, but just be aware that schools are
sometimes not tagged with building=*, just amenity=school.
- This is can go either way, but I would rather see the source= tag on
the changeset rather than each building. The second somebody moves the
building, the source tag is now wrong.
- I did not see any multiple addresses on the larger buildings. How is
that being handled?
- On Paul's comment about the addresses on the garages. The statewide
MassGIS address file that is coming in the summer also puts the
addresses on the garages. It is not clear to me what the best/correct
behavior is. The garage does have that address, it is not wrong. At
the same time it does not seem that useful for us either. I was
planning on talking about this issue. Perhaps we could start a new
thread and talk about what to do when imported data has addresses over
all of the buildings on the parcel.

Since you have only 10 huge files. It would not be a big deal to
simply open them in JOSM, select all, simplify, then save them out.
You can change the default simplification level in JOSM with the
simplify-way.max-error preference. I set it to 1.5 meters. I think it
defaults to 5 meters, you should play with it on your data set.

I have a python script used for the MA building import that can break
these files into smaller chunks and without messing up the relations.
It is tricky to do this in JOSM.

I have a second python script that can make an OSM file of all the
duplicate buildings in a state. After you upload, you can fix up any
dups by hand. The duplicate building script requires a postgis
database. If you have this setup already, you could run it yourself.

It will be around 24 hours to upload all of this data. I have a script
to do this as well, if you don't want to sit in front of JOSM for that

If you are interested in any of this code, let me know off list. I can
send you the code, or I could run some of them for you.


On Sat, May 4, 2013 at 12:03 AM, Matthew Petroff
<openstreetmap at mpetroff.net> wrote:
> Hello,
> The City of Baltimore provides a large amount of public domain GIS data through
> their data portal [1]. Included are city wide building footprints [2], which I
> would like to import into OpenStreetMap. Other users have already started
> importing this data in a less automated way. I confirmed with the city GIS
> office that the data is indeed public domain.
> Using QGIS, I assigned approximate street addresses to each building using a
> parcel map [3] and used the field calculator to clean up the labels and remove
> abbreviations. In addition, I removed all data that intersected with existing
> buildings to preserve existing work. I then separated the data into smaller
> chunks and converted the Shapefiles to OSM with Merkaartor. After simplifying
> Merkaartor's output using osmconvert's "--drop-author" switch, I tagged the
> data with sed, before finally using JOSM to remove duplicate vertices and empty
> tags. My only qualm with the data is that some buildings have more nodes than
> they need, but I'm not sure what can be done about it besides manually reviewing
> and simplifying all 200k+ outlines.
> I've currently tagged the data with:
> building=yes
> addr:city=Baltimore
> addr:state=MD
> addr:country=US
> addr:inclusion=estimate
> source=Baltimore City GIS
> addr:housenumber=[Based on parcel data]
> addr:street=[Based on parcel data]
> I've uploaded the files here for feedback:
> http://db.tt/P9qh1hIm
> Thoughts, suggestions, questions?
> -Matthew Petroff
> [1] https://data.baltimorecity.gov/
> [2] https://data.baltimorecity.gov/Geographic/Building-Footprint-Shape/deus-s85f
> [3] https://data.baltimorecity.gov/Geographic/Parcels-Shape/jk3c-vrfy
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