终于知道ipod touch/iphone是怎样利用wifi信号定位啦

这是一直以来觉得很神奇的技术。对于到处都有详解的gps技术来说，这个技术的说明还真不多，尤其是中文的。

原来和google街景车一样，有个叫skyhook的公司雇了车子自动收集wifi热点的mac地址和相应地理坐标，存在一个数据库里。机子的google map打开后自动把所有wifi热点（包括没有连上的）mac数据联网在skyhook的数据库查找到对应坐标。然后根据信号强弱，用三角测位法计算出大致的位置。知道后就感觉很简单。只是收集数据工作成本比较高。

Skyhook has your router listed

If you live or work in one of these cities, Skyhook's WPS technology is certainly effective and the way it works is quite ingenious.

When an iPhone requests its location using Google Maps, Skyhook's WPS software uses the iPhone's built-in Wi-Fi to scan for nearby access points. It doesn't try to connect to any access points that it finds, it simply collects a MAC address and the Receive Signal Strength Indicator (i.e. the proximity and strength of the 802.11 signal itself) from each one.

The WPS algorithm then compares this data to Skyhook's database of mapped access points. Finally, the WPS algorithm uses both data sets to calculate the iPhone's geographical location.

Read more: http://www.techradar.com/blogs/article/how-the-iphone-s-wi-fi-location-works-201138#ixzz1GxfBOJ8n