Justin: Thank you very much for your support. It was very helpful.
Here I put the answer you gave me and my code so other users may understand
the solution.
The summary of the things I had to do to achieve getting the distance in
meters from one point to another of the city of Cordoba, Argentina:
1. Use the epsg-hsql plugin by modifying the POM.xml file that maven uses
adding the following in the dependencies section:
<dependency>
<groupId>org.geotools</groupId>
<artifactId>gt2-epsg-hsql</artifactId>
<version>2.4-SNAPSHOT</version>
</dependency>
2. Transform the projected coordinates that were in my graph of the city by
searching a correct EPSG code for my data. I found the corresponding epsg
code to my city in this page: http://spatialreference.org/ref/epsg/ and
Justin gave me the right hint on how to transform the coordinates:
/-------------------------------------------- written by Justin
--------------------------------------------------------
Point p = ...;
//create the transformation
CoordinateReferenceSystem crs1 = CRS.decode( "EPSG:4694" );
CoordinateReferenceSystem crs2 = CRS.decode( "EPSG:4326" );
MathTransform tx = CRS.findMathTransform( crs1, crs2, true );
//transform the point
double[] projected = new double[]{ p.getX(), p.getY() };
double[] longlat = new double[2];
tx.transform( projected, 0, longlat, 0, 1 );
After this routine, longlat will contain the longitude and latitude of
the coordinate.
/----------------------------------------------------------------------------------------------------------------------------------
3. Use a GeodeticCalculator to get the distance between the points.
Below I put a very initial version of my code (now working!). Thank you very
much again and hope this helps someone else.
Best regards!
Fran
import org.geotools.graph.structure.Node;
import org.geotools.referencing.CRS;
import org.opengis.referencing.crs.CoordinateReferenceSystem;
import org.opengis.referencing.operation.MathTransform;
import org.geotools.graph.structure.*;
import org.geotools.referencing.GeodeticCalculator;
import com.vividsolutions.jts.geom.Point;
public static double distance(Node orig, Node dest){
double dist;
double[] longlat1, longlat2, projected1, projected2;
Point p1,p2;
CoordinateReferenceSystem crs1, crs2;
MathTransform converter;
dist = -1;
p1 = ((Point) orig.getObject());
p2 = ((Point) dest.getObject());
longlat1 = new double[2];
longlat2 = new double[2];
try{
// Original coordinates, as you can get them from your
graph
proyectadas1 = new double[]{p1.getY(),p1.getX()};
proyectadas2 = new double[]{p2.getY(),p2.getX()};
// POSGAR 94 / Argentina 4:
http://spatialreference.org/ref/epsg/22184/
crs1 = CRS.decode( "EPSG:22184" );
crs2 = CRS.decode( "EPSG:4326" );
converter = CRS.findMathTransform( crs1, crs2, true );
converter.transform( projected1, 0, longlat1, 0, 1 );
converter.transform( projected2, 0, longlat2, 0, 1 );
// geodetic distance calculator
GeodeticCalculator gc = new
GeodeticCalculator(CRS.decode("EPSG:22184"));
gc.setStartingGeographicPoint(longlat1[1],longlat1[0]);
gc.setDestinationGeographicPoint(longlat2[1],longlat2[0]);
dist = gc.getOrthodromicDistance();
System.out.println("Distance: "+ dist);
}catch(Exception e){
e.printStackTrace();
}
return dist;
}
--
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