Implementing GeoSpatial Search Using Lucene 4.X

In this blog post, i am going to explain how to implement GeoSpatial Search using Lucene 4.x.

Problem I am trying to Implement :

Finding Nearest Places Within Certain Radius Given the Location of User.

Sample Input Places Data :

id  name             latitude   longitude

1   Bangalore        12.9558    77.620979
        2   Cubbon Park      12.974045  77.591995      
        3   Tipu Palace      12.959365  77.573792
        4   Bangalore Palace 12.998095  77.592041
        5   Monkey Bar       12.97018   77.61219
        6   Cafe Cofee Day   12.992189  80.2348618

Code :

import java.io.File;

import java.io.IOException;

import org.apache.lucene.analysis.standard.StandardAnalyzer;

import org.apache.lucene.document.Document;

import org.apache.lucene.document.Field;

import org.apache.lucene.document.Field.Store;

import org.apache.lucene.document.FieldType;

import org.apache.lucene.document.IntField;

import org.apache.lucene.document.StoredField;

import org.apache.lucene.index.DirectoryReader;

import org.apache.lucene.index.IndexReader;

import org.apache.lucene.index.IndexWriter;

import org.apache.lucene.index.IndexWriterConfig;

import org.apache.lucene.index.IndexableField;

import org.apache.lucene.queries.function.ValueSource;

import org.apache.lucene.search.Filter;

import org.apache.lucene.search.IndexSearcher;

import org.apache.lucene.search.MatchAllDocsQuery;

import org.apache.lucene.search.ScoreDoc;

import org.apache.lucene.search.Sort;

import org.apache.lucene.search.TopDocs;

import org.apache.lucene.spatial.SpatialStrategy;

import org.apache.lucene.spatial.prefix.RecursivePrefixTreeStrategy;

import org.apache.lucene.spatial.prefix.tree.GeohashPrefixTree;

import org.apache.lucene.spatial.prefix.tree.SpatialPrefixTree;

import org.apache.lucene.spatial.query.SpatialArgs;

import org.apache.lucene.spatial.query.SpatialOperation;

import org.apache.lucene.store.Directory;

import org.apache.lucene.store.SimpleFSDirectory;

import org.apache.lucene.util.Version;

import com.spatial4j.core.context.SpatialContext;

import com.spatial4j.core.distance.DistanceUtils;

import com.spatial4j.core.shape.Point;

import com.spatial4j.core.shape.Shape;

public class SpatialSearch {

private IndexWriter indexWriter;

private IndexReader indexReader;

private IndexSearcher searcher;

private SpatialContext ctx;

private SpatialStrategy strategy;

public SpatialSearch(String indexPath) {

StandardAnalyzer a = new StandardAnalyzer(Version.LUCENE_43);

IndexWriterConfig iwc = new IndexWriterConfig(Version.LUCENE_43, a);

Directory directory;

try {

directory = new SimpleFSDirectory(new File(indexPath));

indexWriter = new IndexWriter(directory, iwc);

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

this.ctx = SpatialContext.GEO;

SpatialPrefixTree grid = new GeohashPrefixTree(ctx, 11);

this.strategy = new RecursivePrefixTreeStrategy(grid, "location");

}

public void indexDocuments() throws IOException {

indexWriter.addDocument(newGeoDocument(1, "Bangalore", ctx.makePoint(12.9558, 77.620979)));

indexWriter.addDocument(newGeoDocument(2, "Cubbon Park", ctx.makePoint(12.974045, 77.591995)));

indexWriter.addDocument(newGeoDocument(3, "Tipu palace", ctx.makePoint(12.959365, 77.573792)));

indexWriter.addDocument(newGeoDocument(4, "Bangalore palace", ctx.makePoint(12.998095, 77.592041)));

indexWriter.addDocument(newGeoDocument(5, "Monkey Bar", ctx.makePoint(12.97018, 77.61219)));

indexWriter.addDocument(newGeoDocument(6, "Cafe Cofee day", ctx.makePoint(12.992189, 80.2348618)));

indexWriter.commit();

indexWriter.close();

}

private Document newGeoDocument(int id, String name, Shape shape) {

FieldType ft = new FieldType();

ft.setIndexed(true);

ft.setStored(true);

Document doc = new Document();

doc.add(new IntField("id", id, Store.YES));

doc.add(new Field("name", name, ft));

for(IndexableField f:strategy.createIndexableFields(shape)) {

doc.add(f);

}

doc.add(new StoredField(strategy.getFieldName(), ctx.toString(shape)));

return doc;

}

public void setSearchIndexPath(String indexPath) throws IOException{

this.indexReader = DirectoryReader.open(new SimpleFSDirectory(new File(indexPath)));

this.searcher = new IndexSearcher(indexReader);

}

public void search(Double lat, Double lng, int distance) throws IOException{

Point p = ctx.makePoint(lat, lng);

SpatialArgs args = new SpatialArgs(SpatialOperation.Intersects,

ctx.makeCircle(lat, lng, DistanceUtils.dist2Degrees(distance, DistanceUtils.EARTH_MEAN_RADIUS_KM)));

Filter filter = strategy.makeFilter(args);

ValueSource valueSource = strategy.makeDistanceValueSource(p);

Sort distSort = new Sort(valueSource.getSortField(false)).rewrite(searcher);

int limit = 10;

TopDocs topDocs = searcher.search(new MatchAllDocsQuery(), filter, limit, distSort);

ScoreDoc[] scoreDocs = topDocs.scoreDocs;

for(ScoreDoc s: scoreDocs) {

Document doc = searcher.doc(s.doc);

Point docPoint = (Point) ctx.readShape(doc.get(strategy.getFieldName()));

double docDistDEG = ctx.getDistCalc().distance(args.getShape().getCenter(), docPoint);

double docDistInKM = DistanceUtils.degrees2Dist(docDistDEG, DistanceUtils.EARTH_EQUATORIAL_RADIUS_KM);

System.out.println(doc.get("id") + "\t" + doc.get("name") + "\t" + docDistInKM + " km ");

}

}

/**

* @param args

* @throws IOException 

*/

public static void main(String[] args) throws IOException {

// TODO Auto-generated method stub

String indexPath = "/home/vishnu/lucene_practices/geo_spatial_index";

SpatialSearch s = new SpatialSearch(indexPath);

//Indexes sample documents

s.indexDocuments();

s.setSearchIndexPath(indexPath);

//Get Places Within 4 kilometers from cubbon park.

s.search(12.974045,77.591995, 4);

}

}

Output :

2 Cubbon Park 0.0 km
4 Bangalore palace 0.5752837176108795 km
3 Tipu palace 2.056590450260357 km
5 Monkey Bar 2.2499941525889806 km
1 Bangalore 3.255797190098085 km

In this blog post we learned how to implement

Basic GeoSpatial Queries like whether a point contains within a circle or not.

My Next Blog Post will talk about how to implement advanced spatial queries like 

geoInterseting - where one polygon intersects with another polygon/line.

geoWithIn - where one polygon lies completely within another polygon.