README.md: Add info on entry points and cellid import, improve

README.md

@@ -1,11 +1,12 @@
 # Offline Location Service
 
-A prototype HTTP location service with Mozilla Location Service (MLS)
-compatible API. Not a web service, but a device-local server with caching
-databases and the aim of minimizing network access and information leakage.
-Designed to be run on Linux with
-[GeoClue](https://gitlab.freedesktop.org/geoclue/geoclue) but may also work
-on other platforms.
+A HTTP location service with Mozilla Location Service (MLS) compatible API.
+Takes a list of locally observed wifi access points and / or mobile cell ids
+and returns a latitude and longitude using various data sources.  Not a web
+service, but a device-local server with caching databases and the aim of
+minimizing network access and information leakage.  Designed to be run on Linux
+with [GeoClue](https://gitlab.freedesktop.org/geoclue/geoclue) but may also
+work on other platforms.
 
 ## Requirements
 
@@ -39,6 +40,10 @@ Python module
 
     python3 -m ols -d debug -C ols.toml
 
+or using the entry point scripts under `bin`
+
+    bin/ols -d debug -C ols.toml
+
 Alternatively, you can make a local install from the source tree with
 [pipx](https://pypa.github.io/pipx/)
 
@@ -74,6 +79,26 @@ The Geoclue demo application can be now used to test the locator:
 If you are running OLS with the debug logging enabled (`-d debug`), OLS should
 now output a lot of log messages and the demo app should print your location.
 
+### Cellid data
+
+If you have a device with a ModemManager supported cell modem, GeoClue will
+receive cellid data and pass it to the location service, i.e. OLS.
+
+Cellid location data can be downloaded in the opencellid CSV format from
+[Mozilla](https://location.services.mozilla.com/downloads) or
+[opencellid.org](https://opencellid.org/) (requires registration).
+
+The `cellid-ols-import` command under `bin` can be used to convert the
+downloaded CSV files to an sqlite3 database which can be used by the 'cellid'
+resolver in OLS. It's very much recommended to use the `--mcc` and `--mnc`
+arguments to `cellid-ols-import`, so that the database contains only the cell
+ids of your operator.
+
+You can use this command to find the MCC and MNC of the cell which your device
+is currently using:
+
+    mmcli -m any --location-enable-3gpp && mmcli -m any --location-get
+
 ## See also
 
  * MicroG