iPhone SDK: CLocationAccuracy. What constants map to what positioning technology?

With respect to CLocationManager docs....

Constant values you can use to specify the accuracy of a location.

extern const CLLocationAccuracy kCLLocationAccuracyBestForNavigation;
extern const CLLocationAccuracy kCLLocationAccuracyBest;
extern const CLLocationAccuracy kCLLocationAccuracyNearestTenMeters;
extern const CLLocationAccuracy kCLLocationAccuracyHundredMeters;
exte开发者_运维知识库rn const CLLocationAccuracy kCLLocationAccuracyKilometer;
extern const CLLocationAccuracy kCLLocationAccuracyThreeKilometers;

Given that, I have the following questions.

1. What triangulation method (GPS, cell tower or wi-fi) corresponds to each accuracy level?
2. Does iPhone SDK utilize Skyhook Wireless API?
3. For kCLLocationAccuracyBestForNavigation, there is note stating the phone must be plugged in. Is this enforced or is it just warning the developer the battery is likely to drain quick from using the GPS receiver.

Thanks in advance.

1. Cell tower triangulation is used in all accuracy modes, I believe, to speed up an initial fix. See Wikipedia.
2. I am myself playing around with kCLLocationAccuracyBestForNavigation. The answer to the question is clearly no. It works perfectly anyway, and for a few hours of data gathering, I can not tell the difference in power consumption (but then I'm doing some CPU-intensive tasks anyway...). My guess from reading the docs is that it uses some Kalman filtering with e.g. accelerometer data, to reduce the number of "off-points".