SpatialQuery for location based search using Lucene

Hi,

My lucene index has got latitude and longitudes fields indexed as follows:

doc.Add(new Field("latitude", latitude.ToString() , Field.Store.YES, Field.Index.UN_TOKENIZED));

doc.Add(new Field("longitude", longitude.ToString(), Field.Store.YES, Field.Index.UN_TOKENIZED));


Term lowerLatitude = new Term("latitude", bounds.South.ToString() );
Term upperLatitude = new Term("latitude", bounds.North.ToString());
RangeQuery latitudeRangeQuery = new RangeQuery(lowerLatitude, upperLatitude, true);
findLocationQuery.Add(latitudeRangeQuery, BooleanClause.Occur.SHOULD);



Term lowerLongitude = new Term("longitude", bounds.West.ToString());
Term upperLongitude = new Term("longitude", bounds.East.ToString());
RangeQuery longitudeRangeQuery = new RangeQuery(lowerLongitude, upperLongitude, true);
findLocationQuery.Add(longitudeRangeQuery, BooleanClause.Occur.SHOULD);



Am facing another problem in this context:
I've one of the documents in the index with the following 3 cities:

- Lyons, IL

Oak Brook, IL

San Francisco, CA

If i give input as "Lyons, IL" then this record comes up when i execute the above search query in Lucene.
But if i give San Francisco, CA as input, then it does not.

However, if i store the cities for this document as follows:

- San Francisco, CA

Lyons, IL

Oak Brook, IL

and when i give San Francisco, CA as input, then this record shows in the search results.

What i want here is that if i type any of the 3 cities in input,I should get this document in the search results.

Is there anything wrong with my search query?
Please help.

Thanks.