A hybrid positioning system for continuously and accurately determining a location of a mobile device is provided. Samples of GPS locations from a pool of mobile devices and accompanying cell tower data, WLAN data, or other comparable network signals are used to construct a dynamic map of particular regions. The dynamic map(s) may be sent to and stored on individual mobile devices such that the mobile device can compare its less accurate, but more readily available, data like cell tower signals to recorded ones and estimate its position more accurately and continuously. The position data may be sent to a server for user in location based services.