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:[EMAIL PROTECTED] > Sent: Sunday, October 31, 2004 9:34 AM > To: [EMAIL PROTECTED] > Cc: [EMAIL PROTECTED] > 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 > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
