There is a significant difference between 2000 and 2010 blocks in Dallas-Fort Worth, as well. But, this difference is mostly caused by more blocks rather that significant change of boundaries. For example, in our region, the number of blocks increased from 98,000 to 157,000 from 2000 to 2010. Yet, if you put the layers on top of each other and count the little slivers that show up due to change of borders, you will get about 180,000 area entities (I think Nancy Reger calls this file pieces-parts). This is according to the files that census web site provides, which Todd Steiss provided the link at http://www.census.gov/geo/www/2010census/t00t10.html. If you create the pieces-parts file yourself, you may end up with significantly more area entities. In our case this number was 653,000. I am not sure why so many more pieces got created, but we think census file made a reasonable assumption and ignored the very little boundary differences to make the pieces meaningful (equivalent of using a thicker market to draw boundaries!). Anyways, if you use the census file, you don't need to create the pieces-parts file. In our experience about 25% of 2010 blocks had one-to-one relation with 2000 blocks. As far as how to compare, some sort of area is the only common component that can be utilized. Census file provides the land area for each "piece" record, which seems to be superior method over total area (note that the difference is water area). If you believe 2010 numbers are good measures for 2000 densities, a weighted method based on 2010 densities can make the process even better. Arash Mirzaei, P.E. Senior Program Manager Model Development and Data Management North Central Texas Council of Governments (NCTCOG) Tel: (817) 695-9261 Fax: (817) 640-3028 Email: amirzaei(a)nctcog.org -----Original Message----- From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Nancy Reger Sent: Wednesday, December 07, 2011 7:37 AM To: ctpp-news(a)chrispy.net Subject: RE: [CTPP] Census Geography Question We've had the same problem- had the same problem in 2000 with changes from the 1990 block too. Sometimes for file with varying polygonal boundaries (TAZ adjustments, block groups, etc), but we've intersected geographies and generated what I call a "pieces-parts file" that has a ton of little parts, and then use the proportion of these new polygons to reallocate data among them and then recompile them. It's not the best way to do things obviously since the data are not really uniformly distributed, but it isolates the ones that are different so you have a smaller set that needs further investigation. Nancy Nancy Reger, AICP Deputy Director, Transportation MORPC 111 Liberty St. Ste. 100 Columbus, Ohio 43215 nreger(a)morpc.org 614-233-4154 -----Original Message----- From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Erlbaum, Nathan (DOT) Sent: Wednesday, December 07, 2011 8:16 AM To: ctpp-news(a)chrispy.net Subject: RE: [CTPP] Census Geography Question We tried this in an attempt to estimate 2010 fhwa adj urban boundary pop based on 2000 fhwa urban boundary and pl dataand we had great difficulty resolving slivers and the cartographic quality differences between the 2000 and 2010 geography files Nathan Erlbaum Associate Transportation Analyst Office of Policy, Planning & Performance New York State Department of Transportation 50 Wolf Road, 6th Floor Albany, New York 12232 (Tel) 518.457.2967 (Fax) 518.457.4944 (E-mail) nerlbaum(a)dot.state.ny.us (Web) www.nysdot.gov ________________________________________ From: ctpp-news-bounces(a)chrispy.net [ctpp-news-bounces(a)chrispy.net] On Behalf Of Ed Christopher [edc(a)berwyned.com] 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 _______________________________________________ ctpp-news mailing list ctpp-news(a)chrispy.net http://www.chrispy.net/mailman/listinfo/ctpp-news

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