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List: qgis-user
Subject: Re: [Qgis-user] Breaking a territory into zones
From: Thayer Young <thayeray () yahoo ! com>
Date: 2021-04-23 20:20:36
Message-ID: 1434299908.504247.1619209236295 () mail ! yahoo ! com
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Hi Jason,
First to answer Nicolas' question, US Census blocks are polygons, they are the \
smallest published unit of the US Census, they are designed to be roughly equal in \
population (very rough in some places), so they vary drastically in size and shape. \
To not reinvent the wheel I would suggest that you search the literature for election \
redistricting. I think you should be very careful about trying to split census blocks \
into finer units. But some states like Maryland do have estimates of the number of \
dwelling units per parcel. This is a recent blog post about using R for computational \
redistricting:https://www.r-bloggers.com/2021/02/some-computational-redistricting-methods-or-how-to-sniff-out-a-gerrymander-in-a-pinch/
QGIS can do K-means clustering, but you should be aware of its pitfalls, for example \
it is likely to give you zones with widely varying population, if the population \
density is not fairly even:https://www.r-bloggers.com/2010/10/k-means-redistricting/ \
-Thayer
On Thursday, April 22, 2021, 12:09:15 AM EDT, qgis-user-request@lists.osgeo.org \
<qgis-user-request@lists.osgeo.org> wrote: > Date: Wed, 21 Apr 2021 16:29:57 -0500
> From: Jason Aleksi <jason.aleski@gmail.com>
> To: qgis-user@lists.osgeo.org
> Subject: [Qgis-user] Breaking a territory into zones
> Message-ID: <CALN462aKOBi6SgfqEgPHs=8HjVE+W5C=L5nCkTi0hg_jG4tMqQ@mail.gmail.com>> \
> Content-Type: text/plain; charset="utf-8"
> Can someone point me in the right direction? I am not sure what I should
> be searching for in reference to the task below.
>
> I work for a non-profit organization. Up to this point, my limited GIS
> knowledge has been focused around plotting and integrating data with qGIS.
> I am tasked with finding a way to analyze the data and build "zones" within
> a territory based on the data with a street line center file. I have
> searched for building zones, districts, territories, heatmaps, spatial
> statistics, voting districts, etc. I found some information relating to
> ESRI Business Analyst, but that was specific to ArcMap and did not point
> me in a related direction.
>
> Here is the data I have:
>
> - Centerline File from the State GIS Office
> - US Census Block Level data from 2010
> - Various boundary files from the State GIS Office
>
> What I am trying to do is break an territory up into 5 zones. Each zone
> should have an equal number of residents. Zone borders are limited to the
> edges of the territory. Within the territory, zone borders should follow
> the nearest street centerline.
>
> Can anyone offer a better direction, keywords to search for, or a feature I
> should look at within qGIS?
>
> -JA-
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<html><head></head><body><div class="ydpd20e5003yahoo-style-wrap" \
style="font-family:Helvetica Neue, Helvetica, Arial, \
sans-serif;font-size:13px;"><div></div> <div dir="ltr" data-setdir="false">Hi \
Jason,</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" \
data-setdir="false">First to answer Nicolas' question, US Census blocks are polygons, \
they are the smallest published unit of the US Census, they are designed to be \
roughly equal in population (very rough in some places), so they vary drastically in \
size and shape.</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" \
data-setdir="false">To not reinvent the wheel I would suggest that you search the \
literature for election redistricting. I think you should be very careful about \
trying to split census blocks into finer units. But some states like Maryland do have \
estimates of the number of dwelling units per parcel.</div><div dir="ltr" \
data-setdir="false"><br></div><div dir="ltr" data-setdir="false">This is a recent \
blog post about using R for computational redistricting:</div><div dir="ltr" \
data-setdir="false"><a \
href="https://www.r-bloggers.com/2021/02/some-computational-redistricting-methods-or-how-to-sniff-out-a-gerrymander-in-a-pinch/" \
rel="nofollow" target="_blank">https://www.r-bloggers.com/2021/02/some-computational-r \
edistricting-methods-or-how-to-sniff-out-a-gerrymander-in-a-pinch/</a><br></div><div \
dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">QGIS can \
do K-means clustering, but you should be aware of its pitfalls, for example it is \
likely to give you zones with widely varying population, if the population density is \
not fairly even:</div><div dir="ltr" data-setdir="false"><a \
href="https://www.r-bloggers.com/2010/10/k-means-redistricting/" rel="nofollow" \
target="_blank">https://www.r-bloggers.com/2010/10/k-means-redistricting/</a> </div><div \
dir="ltr" data-setdir="false"><br></div><div dir="ltr" \
data-setdir="false">-Thayer</div><div dir="ltr" data-setdir="false"><br></div><div \
dir="ltr" data-setdir="false"><br></div><div><br></div>
</div><div id="ydp57c1fc45yahoo_quoted_9842329969" \
class="ydp57c1fc45yahoo_quoted">
<div style="font-family:'Helvetica Neue', Helvetica, Arial, \
sans-serif;font-size:13px;color:#26282a;">
<div>On Thursday, April 22, 2021, 12:09:15 AM EDT, \
qgis-user-request@lists.osgeo.org <qgis-user-request@lists.osgeo.org> wrote: \
</div> <div>> Date: Wed, 21 Apr 2021 16:29:57 -0500<br></div><div><div \
dir="ltr">> From: Jason Aleksi <<a href="mailto:jason.aleski@gmail.com" \
rel="nofollow" target="_blank">jason.aleski@gmail.com</a>><br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span>To: <a \
href="mailto:qgis-user@lists.osgeo.org" rel="nofollow" \
target="_blank">qgis-user@lists.osgeo.org</a><br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span>Subject: [Qgis-user] \
Breaking a territory into zones<br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span>Message-ID: \
<CALN462aKOBi6SgfqEgPHs=8HjVE+W5C=<a \
href="mailto:L5nCkTi0hg_jG4tMqQ@mail.gmail.com" rel="nofollow" \
target="_blank">L5nCkTi0hg_jG4tMqQ@mail.gmail.com</a>></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span>Content-Type: \
text/plain; charset="utf-8"<br></div><div dir="ltr" data-setdir="false"><span><span \
style="color: rgb(38, 40, 42); font-family: Helvetica Neue, Helvetica, Arial, \
sans-serif;">> </span></span><br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span>Can someone point me in \
the right direction? I am not sure what I should<br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span>be searching for in \
reference to the task below.<br></div><div dir="ltr" data-setdir="false"><span><span \
style="color: rgb(38, 40, 42); font-family: Helvetica Neue, Helvetica, Arial, \
sans-serif;">> </span></span><br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span>I work for a non-profit \
organization. Up to this point, my limited GIS<br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span>knowledge has been \
focused around plotting and integrating data with qGIS.<br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span>I am tasked with finding \
a way to analyze the data and build "zones" within<br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span>a territory based on the \
data with a street line center file. I have<br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span>searched for building \
zones, districts, territories, heatmaps, spatial<br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span>statistics, voting \
districts, etc. I found some information relating to<br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span>ESRI Business Analyst, \
but that was specific to ArcMap and did not point<br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span>me in a related \
direction.<br></div><div dir="ltr" data-setdir="false"><span><span style="color: \
rgb(38, 40, 42); font-family: Helvetica Neue, Helvetica, Arial, \
sans-serif;">> </span></span><br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span>Here is the data I \
have:<br></div><div dir="ltr" data-setdir="false"><span><span style="color: rgb(38, \
40, 42); font-family: Helvetica Neue, Helvetica, Arial, \
sans-serif;">> </span></span><br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span> - Centerline \
File from the State GIS Office<br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span> - US Census \
Block Level data from 2010<br></div><div dir="ltr" data-setdir="false"><span><span \
style="color: rgb(38, 40, 42); font-family: Helvetica Neue, Helvetica, Arial, \
sans-serif;">> </span></span> - Various boundary files from the State \
GIS Office<br></div><div dir="ltr" data-setdir="false"><span><span style="color: \
rgb(38, 40, 42); font-family: Helvetica Neue, Helvetica, Arial, \
sans-serif;">> </span></span><br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span>What I am trying to do \
is break an territory up into 5 zones. Each zone<br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span>should have an equal \
number of residents. Zone borders are limited to the<br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span>edges of the \
territory. Within the territory, zone borders should follow<br></div><div \
dir="ltr" data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: \
Helvetica Neue, Helvetica, Arial, sans-serif;">> </span></span>the nearest \
street centerline.<br></div><div dir="ltr" data-setdir="false"><span><span \
style="color: rgb(38, 40, 42); font-family: Helvetica Neue, Helvetica, Arial, \
sans-serif;">> </span></span><br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span>Can anyone offer a \
better direction, keywords to search for, or a feature I<br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span>should look at within \
qGIS?<br></div><div dir="ltr" data-setdir="false"><span><span style="color: rgb(38, \
40, 42); font-family: Helvetica Neue, Helvetica, Arial, \
sans-serif;">> </span></span><br></div><div dir="ltr" \
data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: Helvetica \
Neue, Helvetica, Arial, sans-serif;">> </span></span>-JA-<br></div><div \
dir="ltr" data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: \
Helvetica Neue, Helvetica, Arial, sans-serif;">> </span></span>-------------- \
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sans-serif;">> </span></span>An HTML attachment was scrubbed...<br></div><div \
dir="ltr" data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: \
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dir="ltr" data-setdir="false"><span><span style="color: rgb(38, 40, 42); font-family: \
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