[Talk-us] parcel data next steps

Brian May bmay at mapwise.com
Fri Feb 22 05:04:53 UTC 2013

On 2/21/2013 7:27 PM, Brian Cavagnolo wrote:
> Hey guys,
> In a previous thread on parcel data, some people expressed interest in
> participating in creating some sort of open repository for parcel
> data.  I was imagining a conference call or something to discuss next
> steps, but I think we can advance with email.  I'm imagining that it
> makes sense to separate the data gathering process from the data
> standardization/import process.
> Regarding the data gathering, the main objective is to gather recent
> raw data, licensing terms, and meta data from jurisdictions in
> whatever form they make it available, organize it in a dumb directory
> structure.  I was just going to set up an FTP (read-write)  and HTTP
> (read-only) server to get this going.  Are there any
> recommendations/opinions on a longer-term approach here?  Custom
> webapp?  Off-the-shelf webapp?  Somebody mentioned a git repository.
> Regarding standardization/import, I was planning on setting up an
> empty instance of the rails port as a test bed.  Then participating
> users could point JOSM and other tools at this alternative rails port
> to examine, edit, and import parcel data.  We could also provide
> planet-style dumps and mapnik tiles.  The idea is that we would have a
> safe place to screw up and learn.  Does this sound like a reasonable
> direction?
> Oh, and I found this fantastic paper that some parcel data people (Abt
> Associates, Fairview Industries, Smart Data Strategies) recently put
> together for HUD [1] that examines many of the issues that they faced
> building a parcel database.  Timely.
> Ciao,
> Brian
> [1] http://nationalcad.org/download/the-feasibility-of-developing-a-national-parcel-database-county-data-records-project-final-report/
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Hi Brian,

I am interested in collaborating on this. So here's some thoughts:

 From my perspective (and I think others as mentioned in other email 
threads), the main thrust of utilizing parcels is a source of addresses 
based on parcel centroids where address points or buildings with 
addresses are not available. In addition, several people have mentioned 
they utilize parcels as an overlay to assist with digitizing. The 
current consensus is that parcels should not be imported as a whole.

I think this project needs to dovetail / build upon the work that Ian 
Dees started with finding sources of address data. Parcel polygons are 
one potential source. However, parcel polygons are valuable by 
themselves, so we should be documenting all available sources of parcel 
data as we pursue addresses.

I also think we need a little bit more sophisticated Data Catalog than a 
google spreadsheet. We need to capture more information and a 
spreadsheet gets a bit unwieldy after so may columns. I've got a 
prototype that I am working on getting out in the wild soon, but 
basically its a web form that people register to use and the info sits 
in a database.

A by-product of the effort to identify, catalog, gather raw data, etc. 
would be having a central location for storing raw parcel data that is 
not readily downloadable. For example, someone happens to have a copy of 
X county parcel data that they had to send a check for $25 to acquire, 
they received it on CD, and they would like to donate it to a central 
repository. This is assuming there are no restrictions on the data. It 
sounds like you're willing and able to donate disk and bandwidth to 
support this effort. I don't see a need to make a copy of data that is 
already sitting on the web.

As far as standardization/import and the rails server - I think this is 
not the right path to take. As mentioned above, we shouldn't be 
wholesale importing parcels. Now you could do some standardization of 
parcel data for example to render polygons by land use codes and show 
single family, multi-family, commercial, government, etc land use types 
as an overlay layer for reference, but that is a huge effort by itself. 
Users knowledgeable about parcels in their state or local area could 
serve up something like this as a reference, but the goal is not to 
standardize the parcels and import them.

So, continuing on from the raw data gathering, taking it one step 
further, some organization could gather up the freely downloadable data 
plus the data sitting in this repository and serve up a WMS layer or 
tiles of parcel polygons. And this could be the goto source for a parcel 
overlay for the OSM community members interested in utilizing a parcel 
overlay layer for editing.

Email and a wiki page sounds good to me for coordination. Maybe we can 
bring it up in a Mappy Hour as well. And if there's enough of a need, we 
could do a separate parcels / address oriented Google Hangout. Sounds 
like Serge is already organizing something similar, and maybe we just 
particpiate in that to start, since there's a lot of overlap.

Thanks for sharing the link to that document. Its an awesome document. 
For anyone wanting to learn more about national parcel data issues - 
this is it! I know one of the authors, and all three of them have been 
studying and thinking about this issue for literally decades. Its a 
great read, if you're into that kind of thing.


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