Comments on: Building Construction Date Map, 1990

By: stiefve

stiefve — Fri, 13 Jul 2012 20:17:37 +0000

Pearl, that is.

By: stiefve

stiefve — Fri, 13 Jul 2012 20:17:17 +0000

Thanks, GeoGeek! That’s a useful map. Lots of building happening in Alberta/Vernon and Outer Southeast, which seems consistent with anecdotal and media stories about gentrification and population growth outside of downtown and inner-ring neighborhoods in the last 15-20 years (with the exception of the Pear, of course).

A bit off-topic, but I’d love to see something like the Manahatta project (http://welikia.org/) done for Portland.

By: GeoGeek

GeoGeek — Fri, 13 Jul 2012 19:45:24 +0000

Also, ask and ye shall receive. Here’s a quick and dirty (emphasis on the dirty) map of properties built in Portland since 1990, inclusive. It’s based on Metro’s May 2012 RLIS data set.

It’s a PDF (9MB) and you should be able to zoom in and see a good bit of detail. If I get really ambitious, it wouldn’t be too hard to throw this up as a browsable web map, but hey, I’m doing this while I’m work, so don’t ask too much.

https://dl.dropbox.com/u/1352595/PDX_Since_1990.pdf

By: GeoGeek

GeoGeek — Fri, 13 Jul 2012 19:37:07 +0000

Actually, it’s not that hard to get snapshot data from different points in the past, and use those to generate the data – at least for stuff that’s been recorded on computers.

Examples of this have been done. The Atlas of Oregon has several maps showing building change over time in the downtown area. I suspect much of that data comes from Sanborn maps.

There have been various efforts to digitize Sanborn maps from different places around the country, but I don’t know of the current state of any of that in the Portland area. It wouldn’t be cheap to do so, so there’s probably not enough need for such things to justify the expense.

Now, that being said, it does seem that the city has spent a fair amount of effort digitizing the historical building (and presumably demolition) permits, but I don’t know the state of that data.

By: secretarts

secretarts — Fri, 13 Jul 2012 19:26:59 +0000

Yes, stiefve is right, as far as the data I’ve been able to find, it’s from property tax records. It’s in theory possible to come up with a such an overlay, but I think too much data loss or errors would creep in with the method suggested. Maybe someday when I have time I’ll try!

By: stiefve

stiefve — Fri, 13 Jul 2012 19:20:24 +0000

I’m guessing this data comes from the Multnomah County property tax records, which track when buildings are constructed. Buildings that were torn down and replaced would no longer appear in the dataset, so it seems like it would be difficult to track buildings that have been lost. But maybe you could get at building losses by tracking the number of lot divisions, demolition permits, or other data that would indicate a change to the structures on a tax lot. It would be pretty painstaking, though.

By: portlandpreservation

portlandpreservation — Fri, 13 Jul 2012 16:33:17 +0000

What would be fascinating is an overlay showing what was around from 1910 or earlier in 1990 versus 2010. That way people could see what has been lost in the past two decades.

By: secretarts

secretarts — Fri, 13 Jul 2012 14:16:36 +0000

I’ve actually built a tool to display buildings by age, and my data goes all the way up to 2010. I’d be happy to adjust it to show the most recent info if anyone’s interested.