问题描述
我可以做一个简单的计算，将km转换为一个值，将该值添加到lat或lon float中，以计算搜索的边界框吗？
Is there a simple calculation I can do which will convert km into a value which I can add to a lat or lon float to calculate a bounding box for searches? It doesn't need to be completely accurate.
例如：如果我得到了英国伦敦的经纬度（51.5001524，-0.1262362），我想计算从该点向东/向西25公里处的纬度是什么，到该点向北/南北25公里处的纬度应该是什么，我需要怎么做才能将25公里转换为十进制以添加到上面的值中？
For instance: if I were given a lat/lon for London, England (51.5001524, -0.1262362) and I wanted calculate what the lat would be 25km east/west from that point, and what the lon would be 25km north/south of that point, what would I need to do to convert the 25km into a decimal to add to the values above?
我正在寻找一般的经验法则，即：1km == +/- 0.XXX
I'm looking for a general rule-of-thumb, ie: 1km == +/- 0.XXX
编辑：
我最初搜索 lat lon没有返回此结果：
My original search for "lat lon" didn't return this result:
接受的答案似乎足以满足我的要求。
The accepted answer seems adequate for my requirements.
推荐答案
大概的转换是：
- 纬度：1度= 110.574公里
- 纵向e：1度= 111.320 * cos（纬度）公里
对于地球的极地平坦化而言，这并不完全正确-为此，您可能需要使用WGS84参考椭球（用于GPS的模型）更复杂的公式。但是对于您而言，该错误可能可以忽略不计。
This doesn't fully correct for the Earth's polar flattening - for that you'd probably want a more complicated formula using the WGS84 reference ellipsoid (the model used for GPS). But the error is probably negligible for your purposes.
来源：
注意：请注意，表示的是经纬度坐标以度为单位，而大多数（所有）语言中的 cos 函数通常接受弧度，因此是必需的。
Caution: Be aware that latlong coordinates are expressed in degrees, while the cos function in most (all?) languages typically accepts radians, therefore a degree to radians conversion is needed.
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