這是一直以來覺得很神奇的技術。對於到處都有詳解的gps技術來說，這個技術的說明還真不多，尤其是中文的。
原來和google街景車一樣，有個叫skyhook的公司僱了車子自動收集wifi熱點的mac地址和相應地理座標，存在一個數據庫裏。機子的google map打開後自動把所有wifi熱點（包括沒有連上的）mac數據聯網在skyhook的數據庫查找到對應座標。然後根據信號強弱，用三角測位法計算出大致的位置。知道後就感覺很簡單。只是收集數據工作成本比較高。
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
