Java:三角函数和双重误差导致NaN [英] Java: Trigonometry and double inaccuracy causing NaN

问题描述

我有一个使用纬度和经度的距离公式:

I have a distance formula using latitude and longitude:

distance = EARTH_MILES_RADIUS
    * Math.acos(Math.sin(lat1 / RADIAN_CONV)
    * Math.sin(lat2 / RADIAN_CONV)
    + Math.cos(lat1 / RADIAN_CONV)
    * Math.cos(lat2 / RADIAN_CONV)
    * Math.cos((lng2 - lng1) / RADIAN_CONV));

lat1，lng1，lat2，lng2是双重原语.它们作为双重原语来到我的身边，对此我无能为力.

lat1,lng1,lat2,lng2 are double primitives. They come to me as double primitives and there is nothing I can do about it.

问题是当我有一对相同的经度或纬度时，该公式有时会返回NaN.我相信这是因为我采用的反余弦数要稍微大于1，而实际上应该恰好是1.如果这些点也是对立的，那么它们可能会比-略小- 1.

The problem is that when I have a pair of longitude or latitudes that are the same the formula sometimes returns NaN. I believe this is because I am taking the arc cosine of a number very slightly greater than 1, when in fact it should be exactly 1. I would probably have problems if the points were antipodal as well, where they might be slightly less than -1.

如何最好地解决此问题?

How can I best fix this problem?

推荐答案

只需检查相等性即可解决我的问题:

Simply checking for equality was enough to fix my problem:

if (lat1 == lat2 && lng1 == lng2) ...

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