https://f-droid.org/packages/com.google.android.gms backend that uses <a href="http://opencellid.org">OpenCellID</a>.

Location calculation is done onboard and works without network connectivity. The

cell-tower based lookup for your current location is implemented via a included

binary cell database extracted from <a href="http://opencellid.org">OpenCellID</a>.

This "NetworkLocationProvider" works without network connectivity and will never

post your data anywhere. You are thus encouraged to help OpenCellID to gather

more cells in order to improve this project.

https://f-droid.org/packages/de.enaikoon.android.keypadmapper3 can be used to gather cell information for

OpenCellID.

<b>Warning:</b> This app drains battery and seems no longer maintained.

Creator