Java Geocalc

Geocalc is a simple java library aimed at doing arithmetics with Earth coordinates. It is designed to be simple to embed in your existing applications and easy to use. Geocalc can:

1. Calculate the distance between to coordinates
2. Find a point at X distance from a standpoint, given a bearing
3. Calculate a rectangular area around a point
4. Determine whether a Point is contained within that area
5. Calculate the bearing between two points

This library is being used on www.rentbarometer.com.

How to use

Installing

Download

git clone git@github.com:grumlimited/geocalc.git

Compile

You need a JDK 1.6 and maven.

mvn clean install -DskipTests=true

Embed

<dependency>
    <groupId>com.grum</groupId>
    <artifactId>geocalc</artifactId>
    <version>0.1</version>
</dependency>

Creating a Point, and converting between systems

//Kew, London
Coordinate lat = new DegreeCoordinate(51.4843774);
Coordinate lng = new DegreeCoordinate(-0.2912044);
Point kew = new Point(lat, lng);

double radians = degreeCoordinate.getRadianCoordinate().getRadians();

double minutes = degreeCoordinate.getDMSCoordinate().getMinutes();
double seconds = degreeCoordinate.getDMSCoordinate().getSeconds();
double wholeDegrees = degreeCoordinate.getDMSCoordinate().getWholeDegrees();

minutes = degreeCoordinate.getGPSCoordinate().getMinutes();
seconds = degreeCoordinate.getGPSCoordinate().getSeconds(); // always 0
wholeDegrees = degreeCoordinate.getGPSCoordinate().getWholeDegrees();

Distance between 2 points

The result is given in meters.

//Kew, London
Coordinate lat = new DegreeCoordinate(51.4843774);
Coordinate lng = new DegreeCoordinate(-0.2912044);
Point kew = new Point(lat, lng);

//Richmond, London
lat = new DegreeCoordinate(51.4613418);
lng = new DegreeCoordinate(-0.3035466);
Point richmond = new Point(lat, lng);

double distance = EarthCalc.getDistance(richmond, kew); //in meters

Finding a point at 'distance in meters away' from a standpoint, given a bearing

//Kew
Coordinate lat = new DegreeCoordinate(51.4843774);
Coordinate lng = new DegreeCoordinate(-0.2912044);
Point kew = new Point(lat, lng);

//Distance away point, bearing is 45deg
Point otherPoint = EarthCalc.pointRadialDistance(kew, 45, 0);

Calculating a rectangular area around a point

This is useful when, having a reference point, and a large set of other points, you need to figure out which ones are, say, 3000 meters away.

While this only gives an approximation, it is several order of magnitude faster than calculating the distances from each point in the set to the reference point.

  BoundingArea area = EarthCalc.getBoundingArea(kew, 3000);
  Point nw = area.getNorthWest();
  Point se = area.getSouthEast();

Now, given that rectangle delimited by 'nw' and 'se', you can determine which points in your set are within these boundaries.

Determining whether a Point is contained within a BoundingArea

Now say you have a BoundingArea:

  //somewhere in Europe, not sure where ;-)
  Point northEast = new Point(new DegreeCoordinate(70), new DegreeCoordinate(145));
  Point southWest = new Point(new DegreeCoordinate(50), new DegreeCoordinate(110));
  BoundingArea boundingArea = new BoundingArea(northEast, southWest);
  
  Point point1 = new Point(new DegreeCoordinate(60), new DegreeCoordinate(120));
  assertTrue(boundingArea.isContainedWithin(point1)); //true
  
  Point point2 = new Point(new DegreeCoordinate(45), new DegreeCoordinate(120));
  assertFalse(boundingArea.isContainedWithin(point2)); //false

Calculating bearing between two points

//Kew
Coordinate lat = new DegreeCoordinate(51.4843774);
Coordinate lng = new DegreeCoordinate(-0.2912044);
Point kew = new Point(lat, lng);

//Richmond, London
lat = new DegreeCoordinate(51.4613418);
lng = new DegreeCoordinate(-0.3035466);
Point richmond = new Point(lat, lng);

double bearing = EarthCalc.getBearing(kew, richmond); //in decimal degrees