UnifiedNlp backend that uses locally acquired WLAN/Wi-Fi AP and mobile/cellular tower data to resolve user location. Collectively, “WLAN/WiFi and mobile/cellular” signals will be called “RF emitters” below. Conceptually, this backend consists of two parts sharing a common database. One part passively monitors the GPS. If the GPS has acquired and has a good position accuracy, then the coverage maps for RF emitters detected by the phone are created and saved. The other part is the actual location provider which uses the database to estimate location when the GPS is not available. This backend uses no network data. All data acquired by the phone stays on the phone.