RE: [CTPP] Census Geography Question (Blocks)

We're most interested in TAZ zone-level, or place-level stats. (I can't imagine needing Block-level change statistics.) So, we recast all the year 2000 Block polygons as centroid points and use "spatial join" to attach a consistent-over-time TAZ code and place code (most recent jurisdictional boundaries). Then simply roll up Blocks into TAZ totals, place totals, etc. There are Blocks that straddle TAZ and place boundaries - just have to live with that. (I do repeat the step above 2 or 3 times as a quality control: I identify Block centroids using different centroid location options (thus moving the points around) and test to see whether that yields multiple membership in multiple TAZs or places. Then I go to aerial photography and manually recode TAZ and place membership based on "rooftops assessment": which side of the boundary line has the majority of structures, or else the majority of land acreage. This is an issue only in ½ % of Blocks.) Todd Graham | Principal Forecaster Metropolitan Council | 390 North Robert Street | Saint Paul, MN 55101 tel: 1+651-602-1322 | fax: 1+651-602-1674 | e: todd.graham@metc.state.mn.us<mailto:libby.starling@metc.state.mn.us> in: www.linkedin.com/in/toddgraham<http://www.linkedin.com/in/toddgraham> Visit www.metrocouncil.org/data for the latest in regional information. -----Original Message----- From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Uppalapati, Sirisha Sent: Wednesday, December 07, 2011 8:20 AM To: ctpp-news(a)chrispy.net Subject: RE: [CTPP] Census Geography Question Hi, We faced similar situation in Southeast Michigan. In order to accurately depict change over time with geographic areas that also change over time, SEMCOG developed an equivalent "small area" geographic layer. Essentially, the new "blocks" in this geography would be a combination of blocks resulting in having same boundary in both Census 2000 and 2010. Using this new equivalent geography we are producing a series of change maps and analyses at the lowest geographic level possible. Sirisha Uppalapati Data Analysis Group SEMCOG, the Southeast Michigan Council of Governments www.semcog.org -----Original Message----- From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Ed Christopher Sent: Tuesday, December 06, 2011 7:44 PM To: ctpp-news(a)chrispy.net Subject: [CTPP] Census Geography Question Today i got this question from an MPO friend of mine and was hoping others on the list could help me. Anyone experiencing similar issues. ------------- Ed We have experienced the frustration of block boundaries between the 2000 Census and the 2010 Census being dramatically different within our urbanized area. Our GIS experts have had a difficult time assembling and reconciling the differences in order for us to simply compare data on a block-by block basis. Do you know if this is unique to us or are we in the same boat as others? -- Ed Christopher FHWA Resource Center Planning Team 4749 Lincoln Mall Drive, Suite 600 Matteson, IL 60443 708-283-3534 (V) 708-574-8131 (C) _______________________________________________ ctpp-news mailing list ctpp-news(a)chrispy.net http://www.chrispy.net/mailman/listinfo/ctpp-news _______________________________________________ ctpp-news mailing list ctpp-news(a)chrispy.net http://www.chrispy.net/mailman/listinfo/ctpp-news