Android google map 两点之间的距离

public class DistanceHelper {
/** Names for the units to use */
public final static int KILOMETERS = 0;
public final static int STATUTE_MILES = 1;
public final static int NAUTICAL_MILES = 2; /** Radius of the Earth in the units above */
private final static double EARTHS_RADIUS[] = { 6378.1, // Kilometers
3963.1676, // Statue miles
3443.89849 // Nautical miles
}; /** Conversion factor to convert from degrees to radians */
private static final double DEGREES_TO_RADIANS = (180 / Math.PI); /**
* Calculates the "length" of an arc between two points on a sphere given
* the latitude & longitude of those points.
*
* @param aLat
* Latitude of point A
* @param aLong
* Longitude of point A
* @param bLat
* Latitude of point B
* @param bLong
* Longitude of point B
* @return
*/
private static double calclateArc(double aLat, double aLong, double bLat,
double bLong) {
/*
* Convert location a and b's lattitude and longitude from degrees to
* radians
*/
double aLatRad = aLat / DEGREES_TO_RADIANS;
double aLongRad = aLong / DEGREES_TO_RADIANS;
double bLatRad = bLat / DEGREES_TO_RADIANS;
double bLongRad = bLong / DEGREES_TO_RADIANS; // Calculate the length of the arc that subtends point a and b
double t1 = Math.cos(aLatRad) * Math.cos(aLongRad) * Math.cos(bLatRad)
* Math.cos(bLongRad);
double t2 = Math.cos(aLatRad) * Math.sin(aLongRad) * Math.cos(bLatRad)
* Math.sin(bLongRad);
double t3 = Math.sin(aLatRad) * Math.sin(bLatRad);
double tt = Math.acos(t1 + t2 + t3); // Return a "naked" length for the calculated arc
return tt;
} /**
* Calculates the distance between two addresses
*
* @param pointA
* GeoPoint of point A
* @param pointB
* GeoPoint of point B
* @param units
* Desired units
* @return Distance between the two points in the desired units
*/
public static double calculateDistance(GeoPoint pointA, GeoPoint pointB,
int units) {
return calclateArc(pointA.getLatitudeE6() / 1E6,
pointA.getLongitudeE6() / 1E6, pointB.getLatitudeE6() / 1E6,
pointB.getLongitudeE6() / 1E6) * EARTHS_RADIUS[units];
} /**
* Calculates the distance between two locations
*
* @param pointA
* Location of point A
* @param pointB
* Location of point B
* @param units
* Desired units
* @return Distance between the two points in the desired units
*/
public static double calculateDistance(Location pointA, Location pointB,
int units) {
return calclateArc(pointA.getLatitude(), pointA.getLongitude(),
pointB.getLatitude(), pointB.getLongitude())
* EARTHS_RADIUS[units];
}
}