Backends

Network-Location

AppleWifiNlpBackend | F-Droid | GitHub

Uses Apple's service to resolve Wi-Fi locations. It has excellent coverage but the database is proprietary.

AMap UnifiedNlp Backend | IzzyOnDroid | Gitlab

Uses the AMap Location API (a popular location service in China) to resolve locations. The database is proprietary.

Baidu UnifiedNlp Backend | IzzyOnDroid | Gitlab

Uses the Baidu Location API (another popular location service in China) to resolve locations. The database is proprietary.

Déjà Vu Location Service | F-Droid | GitHub

Uses locally acquired WLAN/WiFi AP and mobile/cellular tower data to resolve user location.

LocalGSMLocationProvider | Last update: 2014 | F-Droid | GitHub

Local opencellid based location provider backend. Has been surpassed by LocalGSMBackend which also has an OpenCellID option

LocalWifiNlpBackend | F-Droid | GitHub

Local location provider for Wi-Fi APs using on-phone generated database.

LocalGSMBackend | F-Droid | GitHub

Local location provider for GSM cells. It works offline by downloading freely licensed database files from Mozilla, OpenCellID, or lacells.db.

MozillaNlpBackend | F-Droid | GitHub

Uses the Mozilla Location Service to resolve user location. The coverage is OK. Only the cell tower database is free.

OpenWlanMapNlpBackend | Last updated: 2015 | GitHub

Uses OpenWlanMap.org to resolve user location but the NLP backend did not reach release-quality, yet. Users interested in a freely licensed and downloadable database for offline use should stick with Radiocells for now.

Radiocells.org UnifiedNlp Backend | F-Droid | GitHub

Uses Radiocells.org to resolve user location. Community-created, freely licensed database that can optionally be downloaded for offline operation. The coverage varies from country to country (it's best in central Europe).

Geocoding

NominatimGeocoderBackend | F-Droid | GitHub

Address lookup backend using OpenStreetMap Nominatim service.

Testing

My Location | F-Droid | IzzyOnDroid | Github

Shows your current location as seen by GPS, Network Location and UnifiedNLP

Location Provider Debugger | IzzyOnDroid | Github