[Talk-us] parcel boundaries and associated data in OSM

Brian May bmay at mapwise.com
Thu Feb 14 21:04:36 GMT 2013

On 2/14/2013 3:43 PM, Ian Dees wrote:
> Before this discussion moves forward we should define what "parcel 
> data" is. In my mind it's mostly-abutting polygons representing land 
> ownership. Usually it comes with metadata about tax information and 
> ownership information, and sometimes it has address information for 
> buildings built on that parcel.
> On Thu, Feb 14, 2013 at 2:29 PM, Brian Cavagnolo <bcavagnolo at gmail.com 
> <mailto:bcavagnolo at gmail.com>> wrote:
>     Is parcel data useful to OSM?
> Yes! Parcel data can be useful to help find parks, schools, and other 
> public areas. If it includes addressing information we can extract 
> that to make it easier to map addresses and/or building footprints.
> However, it's my opinion that the parcel polygons themselves should 
> NOT be imported into OSM. There's simply too much data, it can not be 
> improved by other OSM mappers, and abutting polygons are one of the 
> trickiest types of data to get right in the OSM data format.
>     Can parcel data possibly be kept up to date?
> It's possible, but very very difficult. I don't think anyone in OSM 
> has created a reliable two-way sync between external and OSM data. 
> Such a thing has been on lots of people's wishlists for several years.
>     Does parcel data meet the "on the ground" verifiability criteria?
> No. I'm sure there will be at least a couple people that argue against 
> me, but I have yet to be convinced. Parcel data is surveyed by 
> professionals, maintained by the government, and there is very rarely 
> a physical manifestation of the actual parcel boundary.
>     Can tools be adapted to accommodate parcel data density?
> Yes, and OSM will have to get there eventually as our data density 
> increases, but we're not ready for it now.
+1 on all of Ian's comments.

I think we should start with some sort of nationwide parcel data 
clearinghouse. Ian made a good start with the Google Doc to document 
parcel data sources that could be used for obtaining site address data. 
My thought is we should have some kind of data catalog web app for this 
info, where people can register, create/update metadata records as 
needed, and have a bit more functionality than a google spreadsheet.

There's a good bit of parcel data from govmts out there that doesn't 
have licensing restrictions, its cheap/free, but you have to order it 
and its shipped on DVD or ftp. The next step would be to obtain copies 
of this data and put it on the web for anyone to grab. We just need 
someone to host some space/bandwidth. Is that something the US Chapter 
can do? In addition, updates could be made whenever people get the itch. 
Or strive for an annual update. Updates would just be replacing the raw 

Going the next step into standardization to a common format, etc. is a 
huge can of worms. However, just knowing where to grab the data easily 
and having a central spot to grab data that isn't already sitting on the 
web would be a major step forward.


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