不幸的是，API中沒有提供此類功能，因此您必須編寫自己的函數(shù)。
該站點(diǎn)提供了一些涉及緯度/經(jīng)度的計(jì)算以及示例JavaScript代碼。具體來說，標(biāo)題為“給定距離和起點(diǎn)的目標(biāo)點(diǎn)”的部分顯示了如何計(jì)算您的要求。
JavaScript代碼在該頁面的底部，這是將其轉(zhuǎn)換為Objective-C的一種可能方法：
- (double)radiansFromDegrees:(double)degrees
{
return degrees * (M_PI/180.0);
}
- (double)degreesFromRadians:(double)radians
{
return radians * (180.0/M_PI);
}
- (CLLocationCoordinate2D)coordinateFromCoord:
(CLLocationCoordinate2D)fromCoord
atDistanceKm:(double)distanceKm
atBearingDegrees:(double)bearingDegrees
{
double distanceRadians = distanceKm / 6371.0;
//6,371 = Earth's radius in km
double bearingRadians = [self radiansFromDegrees:bearingDegrees];
double fromLatRadians = [self radiansFromDegrees:fromCoord.latitude];
double fromLonRadians = [self radiansFromDegrees:fromCoord.longitude];
double toLatRadians = asin( sin(fromLatRadians) * cos(distanceRadians)
+ cos(fromLatRadians) * sin(distanceRadians) * cos(bearingRadians) );
double toLonRadians = fromLonRadians + atan2(sin(bearingRadians)
* sin(distanceRadians) * cos(fromLatRadians), cos(distanceRadians)
- sin(fromLatRadians) * sin(toLatRadians));
// adjust toLonRadians to be in the range -180 to +180...
toLonRadians = fmod((toLonRadians + 3*M_PI), (2*M_PI)) - M_PI;
CLLocationCoordinate2D result;
result.latitude = [self degreesFromRadians:toLatRadians];
result.longitude = [self degreesFromRadians:toLonRadians];
return result;
}
在JS代碼中，它包含此鏈接，該鏈接顯示了對大于地球周長1/4的距離的更精確的計(jì)算。
另請注意，上面的代碼接受以km為單位的距離，因此請確保在通過之前將米除以1000.0。
