3 Jun
2022
3 Jun
'22
5:35 p.m.
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
3 Jun
3 Jun
6:26 p.m.
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<mailto:egads@epsys.com>
Economic & Planning Systems (EPS)
1330 Broadway, Suite 450
Oakland, CA 94612
T 510-841-9190
http://www.epsys.com<http://www.epsys.com/>
[EPS_Logo_01]
From: Jim Hubbell [mailto:jimhubbell1975@gmail.com]
Sent: Friday, June 03, 2022 14:35
To: ctpp(a)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
4 Jun
4 Jun
5:36 p.m.
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)
* 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.
[cid:image002.jpg@01D87828.D1300600]
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] <https://www.facebook.com/COMPASSIdaho/> [5]
<https://www.instagram.com/compassidaho/> [4]
<https://twitter.com/COMPASSIdaho> [3]
<https://www.youtube.com/user/COMPASSIdaho> [1]
<linkedin.com/company/compassidaho>
From: Edward Sullivan <egads(a)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(a)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<mailto:egads@epsys.com>
Economic & Planning Systems (EPS)
1330 Broadway, Suite 450
Oakland, CA 94612
T 510-841-9190
http://www.epsys.com<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<mailto: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
6:28 p.m.
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<mailto:egads@epsys.com>
Economic & Planning Systems (EPS)
1330 Broadway, Suite 450
Oakland, CA 94612
T 510-841-9190
http://www.epsys.com<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(a)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)
* 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.
[cid:image002.jpg@01D87827.B858BAB0]
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] <https://www.facebook.com/COMPASSIdaho/> [5]
<https://www.instagram.com/compassidaho/> [4]
<https://twitter.com/COMPASSIdaho> [3]
<https://www.youtube.com/user/COMPASSIdaho> [1]
<linkedin.com/company/compassidaho>
From: Edward Sullivan <egads@epsys.com<mailto: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<mailto: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<mailto:egads@epsys.com>
Economic & Planning Systems (EPS)
1330 Broadway, Suite 450
Oakland, CA 94612
T 510-841-9190
http://www.epsys.com<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<mailto: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
9:48 p.m.
Jim,
While the CTPP program encouraged folks to better align their block groups
with their TAZs, doing so, was not universal, and methods to do so varied.
For instance, DVRPC tried to make new block groups more similar to TAZs
(not always successfully) and others said they would just match their TAZS.
Probably what others are indicating makes sense, although I think going off
of strictly intersections of area is less desirable than perhaps weighing
by the population of component blocks when looking at demographic
information or employment of certain blocks if you have some proprietary,
point-level employment source or maybe lehd (although they add a lot of
noise for their geolocation at the block level. Still, if you have block
groups with high concentrations of employment on one side and population on
the other, using strictly area will give you a muddier result.
Ben
On Fri, Jun 3, 2022 at 6:27 PM Edward Sullivan <egads(a)epsys.com> wrote:
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(a)epsys.com
Economic & Planning Systems (EPS)
1330 Broadway, Suite 450
<https://www.google.com/maps/search/1330+Broadway,+Suite+450+%0D%0AOakland,+CA+94612?entry=gmail&source=g>
Oakland, CA 94612
<https://www.google.com/maps/search/1330+Broadway,+Suite+450+%0D%0AOakland,+CA+94612?entry=gmail&source=g>
*T* 510-841-9190
http://www.epsys.com
[image: EPS_Logo_01]
*From:* Jim Hubbell [mailto:jimhubbell1975@gmail.com]
*Sent:* Friday, June 03, 2022 14:35
*To:* ctpp(a)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
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6 Jun
6 Jun
11:34 a.m.
The Summarize Within Geoprocessing Tool in ArcGIS Pro works nicely for this. It allocates
attributes between two polygons layers of different geographies based on the percentage of
overlap. Be sure you use the tool in the Toolbox, not the one in the Analysis ribbon.
They are different.
Dan Seidensticker (he\him\his)
GIS Specialist
From: Jim Hubbell <jimhubbell1975(a)gmail.com>
Sent: Friday, June 3, 2022 4:35 PM
To: ctpp(a)listserv.transportation.org
Subject: [CTPP News] Roll up TAZs to Census Block Groups?
Caution: This email was sent from an external source. Avoid unknown links and
attachments.
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
1153
days inactive
1156
days old
ctpp@listserv.transportation.org
5 comments
5 participants
participants (5)
-
Benjamin Gruswitz -
Edward Sullivan -
Jim Hubbell -
Mary Ann Waldinger -
Seidensticker, Daniel