23 Feb
2012
23 Feb
'12
10:05 a.m.
Dmitry,
It has been an entire decade since I worked on the TAZ geography here in Minneapolis-St.
Paul, so my memory is not as sharp on the subject. The software used in 'TAZUP'
at the time was not as thorough, so to speak, as that used this time around. Visually
scanning the map that was on the computer screen before you often required 'zooming
in' to locate missing polygons; they were often rather difficult to spot. I do not
recall that the software had any 'checks and balances' like it did for the 2010
work effort. Consequently, the situation you indicated could quite possibly have taken
place. I believe that I had a few instances like you described. Fortunately, they were
tiny slivers.
Good luck with the work!
Bob Paddock
Transportation Planning
Metropolitan Council
Bob.paddock(a)metc.state.mn.us
651 / 602-1340
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(a)chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On Behalf Of
Srinivasan, Nanda
Sent: Thursday, February 23, 2012 8:03 AM
To: ctpp-news(a)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(a)chrispy.net [mailto:ctpp-news-bounces@chrispy.net] On Behalf Of
Messen, Dmitry
Sent: Wednesday, February 22, 2012 8:45 PM
To: ctpp-news(a)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>