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Helper classes to calculate Earth distances, bearing, etc.

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grumlimited/geocalc

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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 two coordinates (law of cosines, haversine and vincenty)
  2. Find a point at X distance from a standpoint, given a bearing
  3. Calculate coordinates of a rectangular area around a point
  4. Determine whether a Point is contained within that area
  5. Calculate the azimuth, initial and final bearings between two points (vincenty)

This library is being used onrentbarometer.com.

This library implements in Java lots of ideas fromMovable-Type. Many thanks.

Embed

<repositories>    <repository>        <id>jitpack.io</id>        <url>https://jitpack.io</url>    </repository></repositories><dependency>    <groupId>com.github.grumlimited</groupId>    <artifactId>geocalc</artifactId>    <version>0.6</version></dependency>

Please refer tojitpack.io/#grumlimited/geocalc/0.6 for more information

API

can be found here:

grumlimited.co.uk/geocalc/0.6

Usage

Creating a Point

//Kew, LondonCoordinate lat = Coordinate.fromDegrees(51.4843774);Coordinate lng = Coordinate.fromDegrees(-0.2912044);Point kew = Point.at(lat, lng);

Converting between systems

Allows conversion of a coordinate between degrees, radians, D-M-s and GPS systems,

double radians = degreeCoordinate.toRadianCoordinate().radians;double minutes = degreeCoordinate.toDMSCoordinate().minutes;double seconds = degreeCoordinate.toDMSCoordinate().seconds;double wholeDegrees = degreeCoordinate.toDMSCoordinate().wholeDegrees;minutes = degreeCoordinate.toGPSCoordinate().minutes;seconds = degreeCoordinate.toGPSCoordinate().seconds; // always 0wholeDegrees = degreeCoordinate.toGPSCoordinate().wholeDegrees;

back and forth

Coordinate.fromDegrees(-46.5456)    .toDMSCoordinate()    .toGPSCoordinate()    .toRadianCoordinate()    .decimalDegrees // toGPSCoordinate() implied loss of precision

Distance between 2 points

Spherical law of cosines

//Kew, LondonCoordinate lat = Coordinate.fromDegrees(51.4843774);Coordinate lng = Coordinate.fromDegrees(-0.2912044);Point kew = Point.at(lat, lng);//Richmond, Londonlat = Coordinate.fromDegrees(51.4613418);lng = Coordinate.fromDegrees(-0.3035466);Point richmond = Point.at(lat, lng);double distance = EarthCalc.gcd.distance(richmond, kew); //in meters

Haversine formula

//Kew, LondonCoordinate lat = Coordinate.fromDegrees(51.4843774);Coordinate lng = Coordinate.fromDegrees(-0.2912044);Point kew = Point.at(lat, lng);//Richmond, Londonlat = Coordinate.fromDegrees(51.4613418);lng = Coordinate.fromDegrees(-0.3035466);Point richmond = Point.at(lat, lng);double distance = EarthCalc.haversine.distance(richmond, kew); //in meters

Vincenty formula

//Kew, LondonCoordinate lat = Coordinate.fromDegrees(51.4843774);Coordinate lng = Coordinate.fromDegrees(-0.2912044);Point kew = Point.at(lat, lng);//Richmond, Londonlat = Coordinate.fromDegrees(51.4613418);lng = Coordinate.fromDegrees(-0.3035466);Point richmond = Point.at(lat, lng);double distance = EarthCalc.vincenty.distance(richmond, kew); //in meters

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

otherPoint will be 1000m away from Kew

//KewCoordinate lat = Coordinate.fromDegrees(51.4843774);Coordinate lng = Coordinate.fromDegrees(-0.2912044);Point kew = Point.at(lat, lng);//Distance away point, bearing is 45degPoint otherPoint = EarthCalc.gcd.pointAt(kew, 45, 1000);

BoundingArea

Calculating a rectangular area (BoundingArea) around a point

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

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

  BoundingArea area = EarthCalc.gcd.boundingArea(kew, 3000);  Point nw = area.northWest;  Point se = area.southEast;

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 = Point.at(Coordinate.fromDegrees(70), Coordinate.fromDegrees(145));  Point southWest = Point.at(Coordinate.fromDegrees(50), Coordinate.fromDegrees(110));  BoundingArea boundingArea = BoundingArea.at(northEast, southWest);

you can determine whether a point is contained within that area using:

  Point point1 = Point.at(Coordinate.fromDegrees(60), Coordinate.fromDegrees(120));  assertTrue(boundingArea.contains(point1)); //true    Point point2 = Point.at(Coordinate.fromDegrees(45), Coordinate.fromDegrees(120));  assertFalse(boundingArea.contains(point2)); //false

Bearing between two points

Azimuth bearing - great circle path

//KewCoordinate lat = Coordinate.fromDegrees(51.4843774);Coordinate lng = Coordinate.fromDegrees(-0.2912044);Point kew = Point.at(lat, lng);//Richmond, Londonlat = Coordinate.fromDegrees(51.4613418);lng = Coordinate.fromDegrees(-0.3035466);Point richmond = Point.at(lat, lng);double bearing = EarthCalc.gcd.bearing(kew, richmond); //in decimal degrees

Azimuth bearing - Vincenty formula

//KewCoordinate lat = Coordinate.fromDegrees(51.4843774);Coordinate lng = Coordinate.fromDegrees(-0.2912044);Point kew = Point.at(lat, lng);//Richmond, Londonlat = Coordinate.fromDegrees(51.4613418);lng = Coordinate.fromDegrees(-0.3035466);Point richmond = Point.at(lat, lng);double bearing = EarthCalc.vincenty.bearing(kew, richmond); //in decimal degrees

Final bearing - Vincenty formula

//KewCoordinate lat = Coordinate.fromDegrees(51.4843774);Coordinate lng = Coordinate.fromDegrees(-0.2912044);Point kew = Point.at(lat, lng);//Richmond, Londonlat = Coordinate.fromDegrees(51.4613418);lng = Coordinate.fromDegrees(-0.3035466);Point richmond = Point.at(lat, lng);double bearing = EarthCalc.vincenty.finalBearing(kew, richmond); //in decimal degrees

Mid point - This is the half-way point along a great circle path between the two points.

//KewPoint kew = Point.at(Coordinate.fromDegrees(51.4843774), Coordinate.fromDegrees(-0.2912044));//Richmond, LondonPoint richmond = Point.at(Coordinate.fromDegrees(51.4613418), Coordinate.fromDegrees(-0.3035466));Point midPoint = EarthCalc.gcd.midPoint(richmond, kew) // Point{latitude=51.47285976194266, longitude=-0.2973770580524634}
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