ios 以度/弧度转换纬度/经度？
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Convert Latitude / Longitude in Degree/Radians?
提问by Umair_uas
How can i convert Latitude and longitude in degree/radians? Do you guys any formula or any idea? I want to show it on MapKit. Thanks.....
如何以度/弧度转换纬度和经度？你们有什么公式或任何想法吗？我想在 MapKit 上展示它。谢谢.....
回答by George Johnston
Since Latitude and Longitude are measured in degrees, you can use the following formula to convert to radians, and back to degrees:
由于纬度和经度以度为单位测量，因此您可以使用以下公式转换为弧度，然后再转换为度：
Radians = Degrees * PI / 180
and on the inverse,
相反，
Degrees = Radians * 180 / PI
回答by Nelson
If you look at earth like a sphere, latitude and longitude are already given in units of degrees. Longitude is expressed as -180 degrees (-pi radians) to 180 degrees (pi radians) with 0 degrees centered at the prime meridian. Latitude is expressed as -90 degrees (-pi/2 radians) to 90 degrees (pi/2 radians) with respect to the equator. This is already a spherical coordinate system (depending on the caveats I give below) with earth's radius approximately 6371 km.
如果你把地球看成一个球体，纬度和经度已经以度为单位给出了。经度表示为 -180 度（-pi 弧度）到 180 度（pi 弧度），0 度以本初子午线为中心。纬度表示为相对于赤道的 -90 度（-pi/2 弧度）到 90 度（pi/2 弧度）。这已经是一个球坐标系（取决于我在下面给出的注意事项），地球半径约为 6371 公里。
So just convert by multiplying by pi/180 as you would for convert degrees to radians in any normal sense. If you want to use those radians for doing something specific like calculating distances between two lat/lons then you should look at some pre-existing sources.
因此，只需乘以 pi/180 进行转换，就像在任何正常意义上将度数转换为弧度一样。如果你想用这些弧度来做一些特定的事情，比如计算两个纬度/经度之间的距离，那么你应该查看一些预先存在的来源。
Similar questions have been asked before, i.e. Convert Lat-Lon to Cartesian Coordinates.
之前也有人问过类似的问题，即Convert Lat-Lon to Cartesian Coordinates。
Generally speaking, the 'correct' answer for a lot of conversion quesitons depends on what error is acceptable in your answer (can it be off 1 mile for distances of 20 miles, etc.) and the model of the world is appropriate in your problem domain. The world is better approximated by an ellipsoid (squashed sphere) than a sphere, but it is easier to perform the calculations assuming earth is a sphere and the error introduced can be minimal. Especially if your program is just looking for 'rough' answers that won't be used for, say, engineering projects.
一般来说，许多转换问题的“正确”答案取决于您的答案中可接受的错误（对于 20 英里的距离是否可以偏离 1 英里等）以及世界模型是否适合您的问题领域。用椭球体（压扁的球体）比用球体更能近似世界，但假设地球是一个球体并且引入的误差最小，则更容易执行计算。特别是如果您的程序只是在寻找不会用于工程项目的“粗略”答案。
It is likely that the lat-lons you have are given in a coordinate system called WGS-84 which is what most hardware GPS units use, which assumes an ellipsoid model.
您所拥有的经纬度很可能是在称为 WGS-84 的坐标系中给出的，这是大多数硬件 GPS 单元使用的坐标系，它假定一个椭球模型。
Note that I had a lot more sources, but I guess I have low reputation so I can only post two links. I would suggest reading on wikipedia about WGS-84, earth's radius, spherical coordinates, prime meridian, and equator for some visual references.
请注意，我有更多的来源，但我想我的声誉很低，所以我只能发布两个链接。我建议在维基百科上阅读关于 WGS-84、地球半径、球坐标、本初子午线和赤道的一些视觉参考。
