23 Feb
2012
23 Feb
'12
10:22 a.m.
Hi, Dmitry,
I had an experience similar to the one you describe. CTPP 2000 TAZ data was showing over
1000 population and over 300 households for a zone that was still entirely undeveloped in
2010 Googlemaps imagery. I couldn't figure it out until I imported the CTPP TAZ
geography and when I tapped on that TAZ: a huge, multi-TAZ area surrounding the MPO
boundary lit up. It appeared that population and households in those surrounding areas had
been included in the TAZ inside the MPO boundary.
Census STF1 block group data was correct.
This was a different Texas MPO area than H-GAC covers.
Karen
Karen M. Lorenzini, P.E., AICP
Texas Transportation Institute
512/467-0952, x-12121
k-lorenzini(a)ttimail.tamu.edu
From: ctpp-news-bounces(a)chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On Behalf Of
Messen, Dmitry
Sent: Thursday, February 23, 2012 8:57 AM
To: 'ctpp-news(a)chrispy.net'
Subject: Re: [CTPP] 2000 Census Traffic Analysis Zones
Nanda,
Yes, I know about the generalization; however, it is my understanding that it results in
the simplification of the lines and shouldn't alter the polygon topology.
Nevertheless, we'll go ahead and process the TIGERLine files. But the question
remains: did the Census standards for Traffic Analysis Zones in 2000 geography
specifically allow non-contiguous zones (other than the islands, of course)?
From: ctpp-news-bounces@chrispy.net<mailto:ctpp-news-bounces@chrispy.net>
[mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Srinivasan, Nanda
Sent: Thursday, February 23, 2012 8:03 AM
To: ctpp-news@chrispy.net<mailto:ctpp-news@chrispy.net>
Subject: Re: [CTPP] 2000 Census Traffic Analysis Zones
Dmitry:
When you use the GIS shape file from http://www.census.gov/geo/www/cob/bdy_files.html
you<http://www.census.gov/geo/www/cob/bdy_files.html%20you> are using a
"generalized GIS file." The limitations of these files are listed on the CB
website as follows:
"The generalized files have a much smaller file size than the original file
extraction from the Census Bureau's TIGER database, resulting in faster download and
processing times.
Limitations
Because of coordinate thinning:
1. Cartographic boundary files should not be used for geocoding;
2. Some offshore, redundant, zero population and housing land areas may be absent from
the files;
3. Cartographic Boundary files are not necessarily vertically integrated with previous
boundary file sets."
For smaller geographies such as TAZs, you are better off using a detailed shape file/Any
other GIS file derived from TIGER directly.
Thanks
Nanda
From: ctpp-news-bounces@chrispy.net<mailto:ctpp-news-bounces@chrispy.net>
[mailto:ctpp-news-bounces@chrispy.net] On Behalf Of Messen, Dmitry
Sent: Wednesday, February 22, 2012 8:45 PM
To: ctpp-news@chrispy.net<mailto:ctpp-news@chrispy.net>
Subject: [CTPP] 2000 Census Traffic Analysis Zones
Would anybody know what the deal was with the 2000 Census Traffic Analysis Zones?
I am working with CTPP 2000 Table 3 data. To do some spatial analysis, I turned to census
boundary files for traffic analysis zones
(http://www.census.gov/geo/www/cob/bdy_files.html). I quickly realized that 63 out 2639
zones for the Houston region are represented by 2+ non-adjacent polygons. Does this happen
in other regions as well? Was this delineation done purposefully or perhaps these are
simply errors stemming from TIGERLine 2000?
Any input will be much appreciated.
Thank you.
Dmitry Messen
H-GAC
dmessen@h-gac.com<mailto:dmessen@h-gac.com>