.net – SpatialQuery for location based search using Lucene

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));

I want to retrieve a set of documents from this index whose lat and long values are in a given range.

As you already know, Lat and long could be negative values. How do i correctly store signed decimal numbers in Lucene?
Would the approach mentioned below give correct results or is there any other way to do this?

 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);

Also,I wanted to know how Lucene's ConstantScoreRangeQuery is better than RangeQuery class.

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.
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.

Please help me achieve this.

Thanks.