Question

我正在开发一款使用Geopoints的Android应用程序，我想从另一个Geopoint确定一个Geopoint，一个距离（任何格式）和一个极角。例如，我希望通过手机中的GPS获取我所在位置的北 - 东北（22,5度）100米处的坐标。

我找到的唯一方法是Location.distanceBetween(...)。

Answer 1

Android的实施。此代码非常适合您的应用程序中的单元测试：

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;
}

Answer 2

看看大圆公式：http://en.wikipedia.org/wiki/Great-circle_distance

这应该给你一些关于如何计算距离的提示。

对于给定距离和标题中的点，请检查http://williams.best.vwh.net/avform.htm#LL 这些公式看起来很复杂，但很容易实现;）

从另一个，距离和极角确定Geopoint

2 个答案: