[Qgis-user] US county shared boundaries

[Brent Blumenstein]

I recently downloaded and have used QGIS a little. I am a semi-retired
biostatistician and have no previous experience with GIS systems previously
never had reason to access such.

First off: What an incredible community of GIS users and based on just a
little experience I am stunned by the positive utility of the resource I
have come into.

Here is a somewhat lengthy description of the problem I am trying to solve.
for the length I apologize.

I am attempting to contribute to the betterment of compliance with the
democratic principles in the US Constitution. As such I have undertaken
what I consider to be an important software development project
that requires geographic considerations.

For this project I need to know which counties (juristictional partitions)
in the 50 US states share a border. Data identifying for each state the
counties that share a border is a necessary constraint required for the
methodology being developed. Sharing a border is a surrogate for being a
close neighbor to other counties within the state.

I am currently assessing the plausibility of using the .shp file from the
US census downloaded in

cb_2020_us_all_500k.zip

I have added latitude and longitude border coordinate data using QGIS to be
used for identifying the counties that share a border.

The example I cite is for Massashusetts, but I expect this problem will be
found for some other states but have not looked at all states yet because
this example problem cited brings the project to a halt.

Here is the problem: The border coordinates in the above identified source
do not allow classification of the island counties Dukes and Nantucktet as
sharing a border with the neighboring mainland counties Banstable, Bristol,
and Plymouth. Thus, the border coordinates in this source cannot be used to
identify that these counties "touch," that is, are neighbors. This failure
to identify neighboring counties using border coordinates, that is
touching, is essential to the project. This issue is expected for other
states yet to be assessed.

This problem was identified as follows. When development of the software
for this project was started sources of county touching data was found
quickly for states at web site x <http://randymajors.org/>xx.yyy (identity
purposefully hidden) and could be used without having to learn GIS
software). The Massachusetts coordinate border data downloaded from the
site allowed the above identified neighboring countries to be classified as
touching. Obviously, this file had border coordinates in intervening water
(where applicable) between island counties and the mainland counties. (This
issue does not exist if there is an island that is part of a county.)
Therefore, it was incorrectly assumed that the yet to be assessed states
would also identity touches to island counties.

The issue identified with in data provided from the US census offerings
came about as follows: As I worked through the states using the xxx.yyy
cordinale files I found that there were at least two missing state
coordinate data files. Apparently, the coordinate file part of the
xxx.yyy web site has degenerated from its original content. I have sent a
query to the owner of xxx.yyy concerning these missing files but it has yet
to be answered. But even if these missing files can be provided that does
not meet the goals of the project in an ideal way.

Here is an explanation. Once it was concluded, incorrectly, that touching
data were readily available the development of the methodology proceeded
forward using files from the x <http://randymajors.org/>xx.yyy web site.
The goal of being able to cite US census resources for touching data was
simply deferred because it was assumed a replacement to the use of the
xxx.yyy files would be possible once the success of the software could be
demonstrated (as is now the case). Simply stated, citing the US census
resources as a reference has a superior look-and-feel for the manuscript
being written for submission to a peer-reviewed journal. The intuitive
decision to defer learning how to use GIS software was recently validated
when I was forced to use other sources for touching data, namely the US
census data.

Now, the utility of the software developed in this project is pending until
it can be successfully applied to all remaining states.

Proceeding requires a new source of border coordinate data that can be used
to identify neighboring counties based on touching borders found using
border coordinates that might be in the water. Meanwhile, I will continue
to try to create an algorithm for use of the census data based on
identifying isolation due to water.

Simply stated: HELP!


-- 
Brent A. Blumenstein, PhD
Trial Architecture Consulting
Port Saint Lucie Florida USA
www.TriArcConsulting.com
bab at TriArcConsulting.com
mobile: +1 (206) 390-0081
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