This is actually a (somewhat constrained) traveling salesman problem rather
than requiring a point to point route, so Google Maps routing won't help
you. pgrouting supports traveling salesman but I haven't used it and don't
know what a practical number of points to handle is - traveling salesman is
a complex problem of course. I was out canvassing for the xxxxx campaign
recently (the number of x's is a clue, in my case at least :) !!), so was an
end user of what I assume to be the same system here. Of course I
immediately wondered about a better automated solution than they had also.
I thought it was an interesting problem though so it's worth explaining it
in a little more detail based on my experience. We went out in pairs, and
were each given a package of paper sheets. The cover page had a printed
Google map with markers indicating the houses we were to visit (this was the
same map for both of us). Then behind that we had a set of printed sheets,
one or more per street, listing the houses we needed to visit on each street
in numerical order, with details about the person/people to talk to at that
house. We were just visiting houses of known sporadic supporters and
independents, so it was a subset of houses - in this case it would vary from
maybe 1 to 4 out of every 10 houses. One canvasser had odd numbers and one
even numbers, so you would do opposite sides of the street, so you had
someone in the same general area for support. Often you would have more
houses in a block on one side of the street than the other, so one person
would get ahead of the other. In the area that we were canvassing, the
blocks were long and thin, so we ended up walking along the blocks
"lengthwise" as most of the addresses we had were on the north-south
streets, but it was hard to tell if you were close to a house on one of the
east-west streets (on a different page from the one that you were currently
looking at). We ended up missing out some of these. In total we had 90
houses in the package, 45 each.
So what we really wanted was to each have a list of our 45 houses in a
suitable order for us to visit (as opposed to being listed street by street
in numerical order), with a map showing the route. Doing the odd / even
thing properly is an extra complication (i.e. taking 90 houses and coming up
with two routes, which ideally keep the two people close to each other). The
simplest initial solution to this would probably be to take all 90 houses,
come up with the best route to all those, and then just split it into odd
and even after doing that. If you got that working, then you could look at
something cleverer.
It seems as though for pgrouting you would need to have a reasonable street
network, which you may or may not have. In some cases, especially if you had
a pretty dense set of houses to visit, you might be able to get a reasonable
solution just using the locations of the houses and ignoring streets
altogether - but clearly in some cases this would not work well.
A pragmatic short term solution might be a semi-interactive one - display
the houses to visit on a map, let a user sketch a line visually with an
approximate route, buffer around that and find all the houses close, and
sort them appropriately based on that. And have the ability to highlight any
houses that were not yet added to the route, etc. I suspect that for a short
term solution (which is presumably what you need), given the challenge of
getting a good road network, etc, this approach may be your best bet. It
would need a bit of custom development though, unless someone happens to
have something like that lying around.
Cheers,
Peter.
On Thu, Oct 16, 2008 at 12:01 AM, Josh Livni <[EMAIL PROTECTED]>wrote:
> pgrouting if you have the street data in postgis would be one way.
> tho as long as they're drawing over google maps, why not insert a little
> javascript to use the gmaps api routing?
>
> -josh
>
>
> On Thu, Oct 16, 2008 at 1:03 AM, Jennifer Strahan <[EMAIL PROTECTED]>wrote:
>
>> Hello Geowankers,
>>
>> I'm forwarding this email from a colleague in hopes that someone will
>> have some suggestions to pass on.
>>
>> Thanks for the help.
>>
>> Regards,
>> Jennifer
>>
>> ps. I've stripped out political references.... that's why you'll see
>> xxxxx campaign.
>>
>> -------- Original Message --------
>> Subject: GIS routing question
>> Date: Wed, 15 Oct 2008 14:32:43 -0700 (PDT)
>> From: [EMAIL PROTECTED]
>> To: [EMAIL PROTECTED]
>> CC: [EMAIL PROTECTED], [EMAIL PROTECTED],
>> [EMAIL PROTECTED],
>> [EMAIL PROTECTED], [EMAIL PROTECTED], [EMAIL PROTECTED],
>> [EMAIL PROTECTED], [EMAIL PROTECTED], [EMAIL PROTECTED],
>> [EMAIL PROTECTED]
>> References:
>> <[EMAIL PROTECTED]>
>>
>>
>>
>> Hi All
>>
>> My partner is working for the xxxxx campaign and was asked by the regional
>> campaign office to look for computer-based routing solutions for canvassing.
>>
>> Nationally, all the campaign offices use a networked,
>> web-browser-accessible database called VoteBuilder. It manages contacts and
>> lets field coordinators define canvassing territories by drawing over a
>> Google map.
>>
>> VoteBuilder doesn't construct a route for the canvassers-- that's up to
>> them. In suburban neighborhoods with winding roads and cul-de-sacs it's
>> almost impossible for them to come up with an efficient route that doesn't
>> miss some of the households.
>>
>> Some of the local and regional offices have adopted software solutions for
>> routing, but the techniques aren't being disseminated.
>>
>> I know there's an extension for ArcGIS to do routing. Is this the only
>> solution?
>>
>> Thanks for any suggestions..
>>
>> Louis
>>
>>
>>
>>
>>
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>>
>
>
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--
Peter Batty - President, Spatial Networking
W: +1 303 339 0957 M: +1 720 346 3954
Blog: http://geothought.blogspot.com
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