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From Brian McCallister <bmccallis...@gmail.com>
Subject Re: GIS
Date Mon, 08 Nov 2004 16:09:43 GMT
Heh, geographic queries are an entertaining space. It isn't java, but
it may be worth looking at PostgreSQL's GIS query capabilities, for
some references.

Just to complicate matters, there are many "standard" representations
of GIS space, not just lat/long =(

Would be awesome functionality to have!

-Brian


On Sun, 31 Oct 2004 09:47:25 -0800, Chuck Williams <chuck@manawiz.com> wrote:
> A colleague of mine just remarked that the indexing problem for
> geographical retrieval is a solved problem.  One algorithm is specified
> in this book, Machine Learning by Tom Mitchell:
> http://www.amazon.com/exec/obidos/ASIN/0070428077/qid=1099244886/sr=2-1/
> ref=pd_ka_b_2_1/102-6518692-8636163
> 
> This algorithm in question is a version of the k-nearest neighbor
> problem, which my colleague has seen implemented for search in at least
> one commercial company.
> 
> It's an expensive book -- it's likely the algorithm could be found via
> online searches for free.  Also, there are probably technical
> discussions and specs in more specialized geographical information
> system literature.
> 
> Chuck
> 
>   > -----Original Message-----
>   > From: Chuck Williams [mailto:chuck@manawiz.com]
>   > Sent: Sunday, October 31, 2004 9:41 AM
>   > To: Lucene Developers List
>   > Cc: scoob@mindinmotiontech.com
>   > Subject: RE: GIS
>   >
>   > I for one would love to have this functionality, i.e. would use it
>   > immediately if available and efficient.  It seems the biggest
> problem is
>   > how you are going to index the information.  If you store and index
> the
>   > latitude and longitude for a geographically-positioned document, and
>   > then want to find all such documents with a spherical rectangle or
>   > circle, how do you find the candidates?  As far as I know, Lucene
> does
>   > range searches now by expanding a range into a list of all possible
>   > values within that range.  This is clearly not a reasonable approach
> for
>   > latitudes and longitudes, assuming you need precision on the values
>   > (which I do).  There are potentially reasonable indexing approaches
> that
>   > occur to me (e.g. in addition to precise lat/lon store with each
> object
>   > its grid label in a few different discrete lat/lon grids, or use a
>   > b-tree index of some kind), but this is probably a solved problem
>   > somewhere in the field of geographical information systems.
>   >
>   > After the indexing, the next interesting question would seem to be
> the
>   > scoring, although this seems a much simpler issue.  E.g., a score
>   > related to the distance from the center of the query region would
> seem
>   > to be appropriate.  There should be a mechanism analogous to the
> current
>   > coord so that this could be tuned or turned off, depending on the
> needs
>   > of particular queries within the application.
>   >
>   > My $0.02,
>   >
>   > Chuck
>   >
>   >   > -----Original Message-----
>   >   > From: Guillermo Payet [mailto:gpayet@localharvest.org]
>   >   > Sent: Sunday, October 31, 2004 9:34 AM
>   >   > To: lucene-dev@jakarta.apache.org
>   >   > Cc: scoob@mindinmotiontech.com
>   >   > Subject: GIS
>   >   >
>   >   > Hello,
>   >   >
>   >   > I'm new here, so first of all I'd like to say hello to everyone.
>   >   >
>   >   > So, hi there...
>   >   >
>   >   > I just spent two days trying to get Lucene to handle
> "geographically
>   >   > constricted" searches for our website. (Check out
>   > www.localharvest.org)
>   >   >
>   >   > I got close, but no cigar. (it works, but is very slow)
>   >   >
>   >   > We need to be able to do searches only within a geographicaly
>   > limited
>   >   > set of documents.  (In this case, our member listings)
>   >   >
>   >   > So... I'd like to volunteer to add the needed functions in
> Lucene
>   >   > to:
>   >   >
>   >   >   - build a LatLonField class for geographical coordinates
>   >   >   - build a LatLonRectTerm (or whatever) to define matches
>   >   >     within a latitude/longituded defined rectangle.
>   >   >   - build a LatLonRadiusTerm (or whatever) to define all matches
>   >   >     within X distance from a point (lat,lon).
>   >   >
>   >   > We're now doing all of this through MySQL, which works "ok", but
>   > leaves
>   >   > a lot to be desired for the relevance of search results for a
> lot of
>   >   > searches.  I've already written all the spherical trig functions
> to
>   >   > to do these searches accurately, and I'd love to port them into
>   >   > Lucene.
>   >   >
>   >   > So my questions are:
>   >   >
>   >   >  - Has there been any talk about doing this before?
>   >   >  - Is this a bad idea for any reason?
>   >   >  - What would be the right approach to do this?
>   >   >
>   >   > The fact that Lucene stores and indexes (or seems it seems) all
>   > terms
>   >   > as Strings and that there is no NumericTerm makes me think that
> I
>   >   > might be missing something and that this migh be a much bigger
> deal
>   >   > than I think?
>   >   >
>   >   >         --G
>   >   >
>   >   >
>   >   >
>   >   >
>   >   > --
>   >   > Guillermo Payet
>   >   > L O C A L  H A R V E S T
>   >   > http://www.localharvest.org
>   >   >
>   >   > Every Morning I awake torn between a desire to save the world
> and
>   >   > an inclination to savor it.  This makes it hard to plan the day.
>   >   >
>   >   >
> -E.B.White
>   >   >
>   >   >
>   >   >
>   >
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