手机的高度测量有多准确
手机 GPS 的高度测量有多准确？据我所知，纬度/经度可能会变化数百米，但是高度值中是否存在相同程度的不确定性？
特别是我正在使用 Windows Phone 7，但我确信这个问题也适用于其他移动设备。我预计 GPS 芯片制造商只有少数，而且不同的手机会使用相同的芯片。
这个问题涉及如何计算，但没有提及任何有关准确性或可靠性。
How accurate is the altitude measurement from a mobile phone's GPS? I've gathered that the lat/long can vary by hundreds of meters but is that same level of uncertainty present in the altitude values?
In particular I'm working with Windows Phone 7 but I'm sure that this question applies to other mobile devices. I expect that there are only a few GPS chip manufacturers and the same chip would be used by different phones.
This question deals with how it is calculated but it doesn't mention anything about accuracy or reliability.
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垂直误差指定为 1.5 * 水平误差。您还必须考虑大地测量模型和行星表面之间的局部偏差，因为即使使用局部校正表，大地测量扁球体模型也是近似值。
Vertical error is specified as 1.5 * horizontal error. You must also allow for local deviation between the geodetic model and the planetary surface because the geodetic oblate spheroid model is an approximation only even when local correction tables are in use.
由于三角测量返回空间中的一个点，因此与 X 和 Y 轴一样，Z 轴也会出现同样的误差。
换句话说，它的准确度并不比 LAT/LONG 的准确度高或低。
Since the triangulation hands back a point in space, the same inaccuracies would apply to the Z axis like they do to X and Y.
In other words, it's no more and no less accurate than the accuracy of the LAT/LONG.
我不太了解 iPhone，但海拔通常不如 GPS 的 X、Y 信息准确。 此处 是有关此内容的一些信息来源。
I don't know specifically about the iPhone, but elevation is often much less accurate than X,Y information from a GPS. Here are some sources of information about this.
它需要相当复杂的数学才能完全理解，但任何 GPS 上的高度都不像纬度/经度位置那么准确。
http://weather.gladstonefamily.net/gps_elevation.html
http://gpsinformation.net/main/altitude.htm
http://www.sawmillcreek.org/showthread.php?83752-Do-civilian-GPS- unts-do-accurate-altitude
引用第三个链接 - “高度误差要大得多，因为它是基于卫星的系统。如果你考虑一下，完美读取的最佳卫星位置将是不幸的是，由于您站在地球上，因此排除了一半的球体，因为实际上您需要卫星的视线，甚至排除了有卫星的星座。因此，一般来说，您的修复将是头顶的，这意味着累积误差主要在垂直平面上。所以，我认为临时估计是垂直误差 = 1.5x 水平误差。”
It requires fairly complicated math to understand fully, but no the altitude on ANY gps is not as accurate the lat/long position.
http://weather.gladstonefamily.net/gps_elevation.html
http://gpsinformation.net/main/altitude.htm
http://www.sawmillcreek.org/showthread.php?83752-Do-civilian-GPS-unts-do-accurate-altitude
quote from the third link - "The altitude error is much greater because it is a satellite based system. If you think about it, the best satellite positions for a perfect read are going to be evenly distributed in an imaginary sphere surrounding you. Unfortunately, since you are standing on the earth, that rules out half the sphere because you need line-of-sight to the satellite. As a practical matter, it even rules out a constellation with satellites close to the horizon. So, generally speaking, your fixes will be overhead--which means that the cumulative error is mainly in the vertical plane. So, I think the offhand estimate is vertical error = 1.5x horizontal error."