当我交换参数时,为什么MKMetersBetweenMapPoints会给我不同的结果？

Question

我实际上是在计算x和y坐标中最大和最小点之间的距离MKMapPoints.

为此,我这样做(y轴的最大距离):

MKMapPoint test1, test2;
double dist;
test1.x = 0.0;
test1.y = 0.0;
test2.x = 0.0;
test2.y = MKMapSizeWorld.height;
dist = MKMetersBetweenMapPoints(test2, test1);
NSLog(@"Distance %f",dist);

我在控制台中得到18997878.291251.但是当我将距离计算更改为:

dist = MKMetersBetweenMapPoints(test1, test2);

我得到18873651.664238,所以我不明白有什么区别.我甚至不知道我是否做正确的事情来获得x和y轴的最大距离值.

任何帮助将不胜感激.

Answer 1

我猜这是一个算法问题。当达到一定精度时停止的某种近似。这就是为什么那里没有换向的原因。您可以尝试示例代码来获取地图上两点之间的距离，而无需使用 MKMapPoints：

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- (float) distanceToLPU {\n\n        useDelegate\n\n        CLLocationCoordinate2D pointACoordinate = appDelegate.usrLoc;\n        CLLocation *pointALocation = [[CLLocation alloc] initWithLatitude:pointACoordinate.latitude longitude:pointACoordinate.longitude];\n\n        CLLocationCoordinate2D pointBCoordinate;\n        pointBCoordinate.latitude = [self.latitude doubleValue];\n        pointBCoordinate.longitude = [self.longitude doubleValue];\n\n        CLLocation *pointBLocation = [[CLLocation alloc] initWithLatitude:pointBCoordinate.latitude longitude:pointBCoordinate.longitude];  \n\n        float distanceMeters = [pointALocation distanceFromLocation:pointBLocation];  \n\n        [pointALocation release];\n        [pointBLocation release];  \n\n        NSString *dist = [NSString stringWithFormat:@" (%.0f \xd0\xbc)", distanceMeters];\n        NSLog(@"Distance to this LPU:%@", dist);\n\n        return distanceMeters;\n    }\n

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