Correctly indexing latitude and longitude values in Lucene
lucene, lucene.net
Solution
Here's the bleeding edge about Searching Numerical Fields in Lucene by Uwe Schindler, the expert on the subject. You may need to use the older (and slower) ConstantScoreRangeQuery because Lucene.net is a bit behind Lucene, and the class NumericRangeQuery described in the link was not yet released in Java Lucene.
Problem
Am working on a "US based nearest city search within a given radius" functionality using Lucene API. Am indexing city's lat and long values in Lucene as follows: ``` doc.Add(new Field("latitude", paddedLatitude, Field.Store.YES, Field.Index.UN_TOKENIZED)); doc.Add(new Field("longitude", paddedLongitude, Field.Store.YES, Field.Index.UN_TOKENIZED)); ``` Since Lucene only understands strings and not numbers, am padding lat and long values. For example, if original lat and long are 41.811846 and -87.820628 respectively, after padding,values look like: paddedLatitude -->"0041.811846" and paddedLongitude-->"-087.820628" Am doing the same padding while building the nearest city query(using Lucene's ConstantScoreRangeQuery class). Given the fact that lat and long values could be decimal/negative numbers, is this the right approach to index them so that I would get correct nearest cities in the search results when lucene would perform a number Range/comparison operation on these values? Thanks.