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Added midpoint
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Romain Gallet committed Feb 25, 2018
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21 changes: 13 additions & 8 deletions README.md
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Expand Up @@ -2,13 +2,15 @@ Java Geocalc ![alt text](https://api.travis-ci.org/grumlimited/geocalc.svg?branc
=======

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:
It is designed to be simple to embed in your existing applications and easy to use.

1. Calculate the distance between two coordinates
Geocalc can:

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

This library is being used on [www.rentbarometer.com](http://www.rentbarometer.com).

Expand All @@ -17,14 +19,17 @@ This library implements in Java lots of ideas from [Movable-Type](http://www.mov
## Changelog

### 0.5.4
* added `EarthCalc.midPoint(p1, p2)`
* renamed `EarthCalc.boundingArea()` to `EarthCalc.pointAt(...)`
* renamed `BoundingArea.boundingArea()` to `BoundingArea.around(...)`
* Removed `get...()` out of `Point` and `BoundingArea`
* Added maven javadoc plugin
* added maven javadoc plugin

### 0.5.3
* Changed constructors to default and private visibility
* Removed `get...()` keyword out of `EarthCalc` methods
* changed constructors to default and private visibility
* removed `get...()` keyword out of `EarthCalc` methods
* `EarthCalc.getDistance()` is now `EarthCalc.gcdDistance()`
* Renamed `BoundingArea.isContainedWithin(...)` to `BoundingArea.contains(...)`
* renamed `BoundingArea.isContainedWithin(...)` to `BoundingArea.contains(...)`

### Embed

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40 changes: 30 additions & 10 deletions src/main/java/com/grum/geocalc/EarthCalc.java
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Expand Up @@ -43,6 +43,30 @@ public class EarthCalc {

public static final double EARTH_DIAMETER = 6371.01 * 1000; //meters

/**
* This is the half-way point along a great circle path between the two points.
*
* @param standPoint standPoint
* @param forePoint standPoint
* @return mid point
* @see <a href="http://www.movable-type.co.uk/scripts/latlong.html"></a>
*/
public static Point midPoint(Point standPoint, Point forePoint) {
double λ1 = toRadians(standPoint.longitude);
double λ2 = toRadians(forePoint.longitude);

double φ1 = toRadians(standPoint.latitude);
double φ2 = toRadians(forePoint.latitude);

double Bx = cos(φ2) * cos(λ2 - λ1);
double By = cos(φ2) * sin(λ2 - λ1);

double φ3 = atan2(sin(φ1) + sin(φ2), sqrt((cos(φ1) + Bx) * (cos(φ1) + Bx) + By * By));
double λ3 = λ1 + atan2(By, cos(φ1) + Bx);

return Point.at(Coordinate.fromRadians(φ3), Coordinate.fromRadians(λ3));
}

/**
* Returns the distance between two points at spherical law of cosines.
*
Expand Down Expand Up @@ -154,7 +178,6 @@ public static double vincentyDistance(Point standPoint, Point forePoint) {
* @param standPoint The stand point
* @param forePoint The fore point
* @return (azimuth) bearing in degrees to the North
*
* @see <a href="http://www.movable-type.co.uk/scripts/latlong.html"></a>
*/
public static double vincentyBearing(Point standPoint, Point forePoint) {
Expand All @@ -167,7 +190,6 @@ public static double vincentyBearing(Point standPoint, Point forePoint) {
* @param standPoint The stand point
* @param forePoint The fore point
* @return (azimuth) bearing in degrees to the North
*
* @see <a href="http://www.movable-type.co.uk/scripts/latlong.html"></a>
*/
public static double getVincentyFinalBearing(Point standPoint, Point forePoint) {
Expand All @@ -184,10 +206,9 @@ public static double getVincentyFinalBearing(Point standPoint, Point forePoint)
* @param bearing Direction in degrees
* @param distance distance in meters
* @return forePoint coordinates
*
* @see <a href="http://www.movable-type.co.uk/scripts/latlong.html"></a>
*/
public static Point pointRadialDistance(Point standPoint, double bearing, double distance) {
public static Point pointAt(Point standPoint, double bearing, double distance) {
/**
var φ2 = asin( sin(φ1)*cos(d/R) + cos(φ1)*sin(d/R)*cos(brng) );
var λ2 = λ1 + atan2(sin(brng)*sin(d/R)*cos(φ1), cos(d/R)-sin(φ1)*sin(φ2));
Expand All @@ -201,7 +222,7 @@ public static Point pointRadialDistance(Point standPoint, double bearing, double
double lat2 = asin(sin(rlat1) * cos(rdistance) + cos(rlat1) * sin(rdistance) * cos(rbearing));
double lon2 = rlon1 + atan2(sin(rbearing) * sin(rdistance) * cos(rlat1), cos(rdistance) - sin(rlat1) * sin(lat2));

return Point.at(new RadianCoordinate(lat2), new RadianCoordinate(lon2));
return Point.at(Coordinate.fromRadians(lat2), Coordinate.fromRadians(lon2));
}

/**
Expand Down Expand Up @@ -231,16 +252,15 @@ public static double bearing(Point standPoint, Point forePoint) {
* @param standPoint The centre of the area
* @param distance Distance around standPoint, im meters
* @return The area
*
* @see <a href="http://www.movable-type.co.uk/scripts/latlong.html"></a>
*/
public static BoundingArea boundingArea(Point standPoint, double distance) {
public static BoundingArea around(Point standPoint, double distance) {

//45 degrees going north-west
Point northWest = pointRadialDistance(standPoint, 45, distance);
Point northWest = pointAt(standPoint, 45, distance);

//225 degrees going south-east
Point southEast = pointRadialDistance(standPoint, 225, distance);
Point southEast = pointAt(standPoint, 225, distance);

return new BoundingArea(northWest, southEast);
}
Expand All @@ -251,7 +271,7 @@ private static class Vincenty {
* initialBearing is the initial bearing, or forward azimuth (in reference to North point), in degrees
* finalBearing is the final bearing (in direction p1→p2), in degrees
*/
double distance, initialBearing, finalBearing;
final double distance, initialBearing, finalBearing;

public Vincenty(double distance, double initialBearing, double finalBearing) {
this.distance = distance;
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33 changes: 25 additions & 8 deletions src/test/java/com/grum/geocalc/DistanceTest.java
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Expand Up @@ -135,7 +135,7 @@ public void testBoundingAreaDistance() {
Coordinate lng = Coordinate.fromDegrees(-0.2912044);
Point kew = Point.at(lat, lng);

BoundingArea area = EarthCalc.boundingArea(kew, 3000);
BoundingArea area = EarthCalc.around(kew, 3000);

double northEastDistance = EarthCalc.gcdDistance(kew, area.northEast);
logger.info("North East => " + northEastDistance);
Expand Down Expand Up @@ -187,7 +187,7 @@ public void testBoundingAreaNorthPole() {
Coordinate lng = Coordinate.fromDegrees(0);
Point northPole = Point.at(lat, lng);

BoundingArea area = EarthCalc.boundingArea(northPole, 10000);
BoundingArea area = EarthCalc.around(northPole, 10000);
logger.info("North East => " + area.northEast);
logger.info("South West => " + area.southWest);

Expand All @@ -205,7 +205,7 @@ public void testBoundingAreaNextToLondon() {
Coordinate lng = Coordinate.fromDegrees(-0.1997387000000117);
Point northPole = Point.at(lat, lng);

BoundingArea area = EarthCalc.boundingArea(northPole, 5);
BoundingArea area = EarthCalc.around(northPole, 5);
logger.info("North East => " + area.northEast);
logger.info("South West => " + area.southWest);

Expand All @@ -223,15 +223,15 @@ public void testPointRadialDistanceZero() {
Coordinate lng = Coordinate.fromDegrees(-0.2912044);
Point kew = Point.at(lat, lng);

Point sameKew = EarthCalc.pointRadialDistance(kew, 45, 0);
Point sameKew = EarthCalc.pointAt(kew, 45, 0);
assertEquals(lat.degrees(), sameKew.latitude, 1E-10);
assertEquals(lng.degrees(), sameKew.longitude, 1E-10);

sameKew = EarthCalc.pointRadialDistance(kew, 90, 0);
sameKew = EarthCalc.pointAt(kew, 90, 0);
assertEquals(lat.degrees(), sameKew.latitude, 1E-10);
assertEquals(lng.degrees(), sameKew.longitude, 1E-10);

sameKew = EarthCalc.pointRadialDistance(kew, 180, 0);
sameKew = EarthCalc.pointAt(kew, 180, 0);
assertEquals(lat.degrees(), sameKew.latitude, 1E-10);
assertEquals(lng.degrees(), sameKew.longitude, 1E-10);
}
Expand All @@ -251,7 +251,7 @@ public void testPointRadialDistance() {
double distance = EarthCalc.gcdDistance(kew, richmond);
double bearing = EarthCalc.bearing(kew, richmond);

Point allegedRichmond = EarthCalc.pointRadialDistance(kew, bearing, distance);
Point allegedRichmond = EarthCalc.pointAt(kew, bearing, distance);

assertEquals(richmond.latitude, allegedRichmond.latitude, 10E-5);
assertEquals(richmond.longitude, allegedRichmond.longitude, 10E-5);
Expand Down Expand Up @@ -315,8 +315,25 @@ public void testVincentyBearing() {
lng = Coordinate.fromDegrees(-0.3035466);
Point richmond = Point.at(lat, lng);

//comparing to results from ttp://www.movable-type.co.uk/scripts/latlong.html
//comparing to results from http://www.movable-type.co.uk/scripts/latlong.html
assertEquals(EarthCalc.vincentyBearing(kew, richmond), new DMSCoordinate(198, 30, 19.58).degrees(), 10E-5);
assertEquals(EarthCalc.getVincentyFinalBearing(kew, richmond), new DMSCoordinate(198, 29, 44.82).degrees(), 10E-5);
}

@Test
public void testMidPoint() {
//Kew
Coordinate lat = Coordinate.fromDegrees(51.4843774);
Coordinate lng = Coordinate.fromDegrees(-0.2912044);
Point kew = Point.at(lat, lng);

//Richmond, London
lat = Coordinate.fromDegrees(51.4613418);
lng = Coordinate.fromDegrees(-0.3035466);
Point richmond = Point.at(lat, lng);

//comparing to results from http://www.movable-type.co.uk/scripts/latlong.html
assertEquals(EarthCalc.midPoint(richmond, kew), Point.at(Coordinate.fromDegrees(51.47285976194266), Coordinate.fromDegrees(-0.2973770580524634)));
}

}

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