[EM] Shortest splitline maps with 2010 (2013) data

[Raph Frank]

I have improved the population balancing and the html formatting.

The new link is at

http://raphfrk.com/district/2010/html/index.html

PS
The original mail bounced since my EM membership expired.

On Sun, Nov 27, 2016 at 2:48 AM, Raph Frank <raphfrk at gmail.com> wrote:

> I haven't posted here in a while.
>
> I re-implemented my code in Java to process the 2010 data.  The new code
> can process the shapefiles, so it has information about the block
> boundaries and connectivity.
>
> The software generates tiles that can be viewed online using the Leaflet
> interactive map library.
>
> I tried to make it flexible.  So far it supports "official districts" and
> "splitline".
>
> The latest (splitline) maps can be viewed at this link.
>
> http://raphfrk.com/splitline_2010/html/Alabama.html
>
> (I am not sure how much bandwidth this uses, but hopefully, it doesn't
> kill my webhost.)
>
> Details:
>
> 2010 Census block level data is used.
>
> The census defines an internal point for each block.
>
> The population of the block is considered concentrated at that point.
>
> The state boundary is the boundary of the combination of all the blocks.
>
> When a split is part of the boundary, I use the line.  It doesn't
> recompute the block based boundary.
>
> (Using the block boundaries to determine longest split could be abused
> anyway)
>
> Gnonomic projection is used because the lines are actually great circles.
>
> The shortest splitline algorithm is run using the block internal points.
>
> Once the splitline algorithm completes, I run a post processing step using
> the connectivity data.
>
> This moves isolates blocks into the district that envelops them so that
> the districts are contiguous.
>
> Then it moves blocks that are on the boundary to another district to
> balance population.
>
> The post processor moves at most 0.25% of the population of a state
> around.  In most cases, it is around 0.1%
>
> In many cases the post processor gets the population to a range of 1 or
> 2.  Some maps are harder to balance.
>
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