Android Find Latitude Longitude Of X point From De

问题:

i m working on Android MapView and developing a map based Application. i Need to find an X distance from the Specific Co-ordinates. Direction is not my priority Distance is my priority let say i need to find 100 meters from a particular location any idea on how can i do that Thanks in advance for reading and answering.

回答1:

in order to calculate to find a point on a line a given distance away from an origin, you need to have a bearing (or direction) as well as the distance. Here is a function that will take a starting location, a bearing and a distance (depth) and return a destination location (for Android): You may want to conver it from KM to Meters or whatever.

public static Location GetDestinationPoint(Location startLoc, float bearing, float depth) 
{ 
    Location newLocation = new Location("newLocation");

    double radius = 6371.0; // earth's mean radius in km 
    double lat1 = Math.toRadians(startLoc.getLatitude()); 
    double lng1 = Math.toRadians(startLoc.getLongitude()); 
    double brng = Math.toRadians(bearing); 
    double lat2 = Math.asin( Math.sin(lat1)*Math.cos(depth/radius) + Math.cos(lat1)*Math.sin(depth/radius)*Math.cos(brng) ); 
    double lng2 = lng1 + Math.atan2(Math.sin(brng)*Math.sin(depth/radius)*Math.cos(lat1), Math.cos(depth/radius)-Math.sin(lat1)*Math.sin(lat2)); 
    lng2 = (lng2+Math.PI)%(2*Math.PI) - Math.PI;  

    // normalize to -180...+180 
    if (lat2 == 0 || lng2 == 0) 
    {
        newLocation.setLatitude(0.0);
        newLocation.setLongitude(0.0);
    }
    else
    {
        newLocation.setLatitude(Math.toDegrees(lat2));
        newLocation.setLongitude(Math.toDegrees(lng2));
    }

    return newLocation;
};

回答2:

Just to make the answer from javram into meters and radians instead of degrees.

/**
 * Create a new location specified in meters and bearing from a previous location.
 * @param startLoc from where
 * @param bearing which direction, in radians from north
 * @param distance meters from startLoc
 * @return a new location
 */
public static Location createLocation(Location startLoc, double bearing, double distance) {
    Location newLocation = new Location("newLocation");

    double radius = 6371000.0; // earth's mean radius in m
    double lat1 = Math.toRadians(startLoc.getLatitude());
    double lng1 = Math.toRadians(startLoc.getLongitude());
    double lat2 = Math.asin(Math.sin(lat1) * Math.cos(distance / radius) + Math.cos(lat1) * Math.sin(distance / radius) * Math.cos(bearing));
    double lng2 = lng1 + Math.atan2(Math.sin(bearing) * Math.sin(distance / radius) * Math.cos(lat1), Math.cos(distance / radius) - Math.sin(lat1) * Math.sin(lat2));
    lng2 = (lng2 + Math.PI) % (2 * Math.PI) - Math.PI;

    // normalize to -180...+180
    if (lat2 == 0 || lng2 == 0) {
        newLocation.setLatitude(0.0);
        newLocation.setLongitude(0.0);
    } else {
        newLocation.setLatitude(Math.toDegrees(lat2));
        newLocation.setLongitude(Math.toDegrees(lng2));
    }

    return newLocation;
}