Hi,

 

If TAZ splits across Block Group (or other) geographies are a concern, and a good master address point file is available for the study area, coding the address points by both TAZ and alternate zone location can provide a means of weighting TAZ attribute allocations to the alternate zones.

 

See:

 

Dasymetric Mapping Using High Resolution Address Point Datasets

 

Paul A Zandbergen (2011)

 

https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1467-9671.2011.01270.x

 

 

 

Edward A. Sullivan, III 

Senior Technical Associate 

Email: egads@epsys.com 

 

Economic & Planning Systems (EPS)

1330 Broadway, Suite 450
Oakland, CA 94612
T 510-841-9190
http://www.epsys.com

 

 EPS_Logo_01

 

 

From: Mary Ann Waldinger [mailto:MWaldinger@compassidaho.org]
Sent: Saturday, June 04, 2022 14:36
To: The Census Transportation Products Program Community of Practice/Users discussion and news list <ctpp@listserv.transportation.org>
Subject: [CTPP News] Re: Roll up TAZs to Census Block Groups?

 

Hi Jim,

We “roll up” or aggregate a variety of geographies to other geographies with associated data.

The most effective way we’ve found is within ArcGIS – it’s a multi-step process but highly effective.

  1. Convert TAZ polygon to point (deals with sloppy lines / polygon lines not matching up)
  2. Use spatial join TAZ point to CBG – this will give you a list of the TAZs with the associated CBG but it will not address any TAZ that is split by a CBG – all the TAZ is assigned to one CBG.
  3. Join the TAZ demographic data into the spatial join file
  4. Run a summary stats – provides the total demographics for each CBG (makes a dbf file)
    1. EX. If CBG contained four TAZs and each TAZ had 10 people the table should have a unique CBG record, but a total people count should be 40
  5. Here’s the fun part go back the spatial join file and make a copy
  6. Dissolve on CBG – makes a new CBG file
  7. Join the data (4a) to this dissolved file or the original CBG file
  8. QA / QC

 

I may have missed a step or not used the correct ArcGIS tool name – going from memory…

 

Hope all is well.

 

 

 

  MaryAnn Waldinger | Principal Planner

  Technical Services Team Lead

  Community Planning Association (COMPASS)

  700 NE 2nd Street, Suite 200

  Meridian, ID 83642

  Direct: 208-475-2242 | Main: 208-855-2558

  http://www.compassidaho.org

  2 5 4 3 1

 

 

 

From: Edward Sullivan <egads@epsys.com>
Sent: Friday, June 3, 2022 4:27 PM
To: The Census Transportation Products Program Community of Practice/Users discussion and news list <ctpp@listserv.transportation.org>
Subject: [CTPP News] Re: Roll up TAZs to Census Block Groups?

 

Using something like the MapInfo ProportionOverlap function would allow rollup based on proportional overlap of the TAZ and Block Group or Tract polygons…

 

Edward A. Sullivan, III 

Senior Technical Associate 

Email: egads@epsys.com 

 

Economic & Planning Systems (EPS)

1330 Broadway, Suite 450
Oakland, CA 94612
T 510-841-9190
http://www.epsys.com

 

 EPS_Logo_01

 

 

From: Jim Hubbell [mailto:jimhubbell1975@gmail.com]
Sent: Friday, June 03, 2022 14:35
To: ctpp@listserv.transportation.org
Subject: [CTPP News] Roll up TAZs to Census Block Groups?

 

Hello CTPP Community,

 

Even though TAZs were officially retired by the Census Bureau, a lot of folks in the transportation continue to use the geographies (especially those from 2010). Today a colleague at StreetLight asked if it's possible to roll up TAZs into Census Block Groups. I couldn't recall off the top of my head whether this is possible, and if so, how to do it. It seems to me that TAZ delineation criteria required they nest into Census Tracts, but maybe also into Block Groups?

 

Any thoughts or guidance on this question would be greatly appreciated. Thanks!

 

Jim Hubbell

StreetLight Data