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&name=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]
