從另一個距離，距離和極角確定地理位置

Question

我正在使用地理點的Android應用程序，我想從另一個地理座標點，距離（任何格式）和極角確定地理點。例如，我想在我的手機中獲取由GPS獲得的位置在北北（東經225度）處的100米的座標。

我發現的唯一方法是Location.distanceBetween(...)。

Answer 1

看看大圓公式：http://en.wikipedia.org/wiki/Great-circle_distance

這應該給你如何計算距離的一些提示。

對於一個給定的距離和方位點，檢查http://williams.best.vwh.net/avform.htm#LL 這些公式看起來很複雜，但很容易實現;）

Answer 2

爲Android實現。此代碼非常適合您的應用中的單元測試：

public double radiansFromDegrees(double degrees) 
{ 
    return degrees * (Math.PI/180.0); 
} 

public double degreesFromRadians(double radians) 
{ 
    return radians * (180.0/Math.PI); 
} 

public Location locationFromLocation(Location fromLocation, double distance, double bearingDegrees) 
{ 
    double distanceKm = distance/1000.0; 
    double distanceRadians = distanceKm/6371.0; 
    //6,371 = Earth's radius in km 
    double bearingRadians = this.radiansFromDegrees(bearingDegrees); 
    double fromLatRadians = this.radiansFromDegrees(fromLocation.getLatitude()); 
    double fromLonRadians = this.radiansFromDegrees(fromLocation.getLongitude()); 

    double toLatRadians = Math.asin(Math.sin(fromLatRadians) * Math.cos(distanceRadians) 
           + Math.cos(fromLatRadians) * Math.sin(distanceRadians) * Math.cos(bearingRadians)); 

    double toLonRadians = fromLonRadians + Math.atan2(Math.sin(bearingRadians) 
               * Math.sin(distanceRadians) * Math.cos(fromLatRadians), Math.cos(distanceRadians) 
               - Math.sin(fromLatRadians) * Math.sin(toLatRadians)); 

    // adjust toLonRadians to be in the range -180 to +180... 
    toLonRadians = ((toLonRadians + 3*Math.PI) % (2*Math.PI)) - Math.PI; 

    Location result = new Location(LocationManager.GPS_PROVIDER); 
    result.setLatitude(this.degreesFromRadians(toLatRadians)); 
    result.setLongitude(this.degreesFromRadians(toLonRadians)); 
    return result; 
}