It is similar to the two Range Filter approach except my way is precomputed and probably faster than filtering through a potentially large result set. Also I can quickly compute a rough max distance between two any lat, lon pairs by compairing thier X1.X2.X3... path.
Dennis Watson Sr SW Engineer GUBA.com On Tuesday 21 November 2006 11:05, Chris Hostetter wrote: > I'm not really sure what an approach like this gaines you ... it provides > a mechanism for ensuring that the lat/lon of all results are within a > bounding box arround your start location -- but those bounding boxes > are fixed when building your index. > > couldn't you achieve the same thing using a "lat" field, a "lon" field > and two RangeFilters? ... except now you get variable sized/centered > bounding boxes? > > : Date: Tue, 21 Nov 2006 07:42:29 -0800 > : From: Dennis Watson <[EMAIL PROTECTED]> > : Reply-To: java-user@lucene.apache.org > : To: java-user@lucene.apache.org > : Cc: spamsucks <[EMAIL PROTECTED]> > : Subject: Re: Sorting on distance from a long/lat > : > : Hi, > : > : I apologize if this is slightly off topic. I have not implemented this, > : but the idea came to me after reading another post about measuring > : distance in lucene. It may be completely impractical, however it seems > : it COULD work at least if the area to be indexed could be constrained. > : > : What if you divided the earth up into lets say 100 square blocks. Each > : block would have sides of length x1 with an area x1^2. You could number > : those blocks 0 - 99. Then you could divide each of those blocks into 100 > : blocks with sides of length x2 = x1 / 10 and number these 0 - 99 as well. > : You could do this until you had blocks with sides of length xn and area > : xn^2. > : > : Each one of these blocks would have four corners with a lat and lon. It > : would be fairly easy to tell if one block were in another block. It > : should be fairly easy to tell which set of boxes any lat, lon pair > : belonged to. > : > : It seems then you could specify locations almost like IP addresses: > : > : X1.X2.X3...Xn > : > : where X1 is the 0-99 number of the first largest set of blocks and X2 is > : the 0-99 number of the next smaller set of blocks inside the first X1 box > : and so on. > : > : You could search in lucene for objects within a certain proximity with a > : prefix search: > : > : X1.X2.* > : X1.X2.X3.* > : > : Moreover you would know that the longer the path that matches, the closer > : those objects are (it is fractal in nature). If you needed more > : granularity you could do a prefix search like this down to the smallest > : granularity you have and then perform a greatcircle distance calculation > : on the the results to see if they are close enough. > : > : Of course there might be too many squares to cover the whole Earth. You > : will want to pick a number of boxes which is a power of two so there are > : a "square" number of squares. I think this enables the fractal nature > : described above. You would want the corners of the squares to land on > : predicable lat, lon points. This may be done more easily with some > : measurement systems than another. > : > : Just my $.02... > : > : > : Dennis Watson > : Sr SW Engineer > : GUBA.com > : > : On Monday 20 November 2006 11:05, spamsucks wrote: > : > I am successfully able to search for "nearbys" given a longitude and a > : > latitude. The basic summary of how I do this is that I add 1000 to the > : > long/lat values and use a RangeFilter in my query. > : > > : > In my display results, I display the results ordered by distance from > : > the original long/lat. What I do is calulate the distance for every > : > document in my result from the original long/lat and perform a sort of > : > the distance. > : > > : > Doing the sort this way (calculating the distances for all results > : > documents) feels like I am being inefficient and wasteful with my CPU > : > cycles. In most cases, I am only displaying the closest 10 documents, > : > but I need to calculate the distance for all documents (potentially > : > 1000) in order to come up with the 10 closest. > : > > : > Has anyone wrestled with these questions before? Is there another > : > approache that I can take? > : > > : > Here is my current working implementation, so you can see what I am > : > describing. The long/lat is stored in a database that I use to build > : > up my lucene query/filters > : > > : > http://www.visitpa.com/visitpa/visitNearbyActivities.pa?type=dining&nam > : >e=Co lor+Me+MineThanks,Phillip > : > > : > > : > --------------------------------------------------------------------- > : > 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] > > -Hoss > > > --------------------------------------------------------------------- > 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]
