Ah, cool, this should incorporate location data at least as good as what the networks self-report! (I suspect that these databases, on top of ingesting all geofeed data, do something similar to Wi-Fi positioning, i.e. correlate the IP address of various GPS-enabled devices with their physical location to try and deduce undocumented/non-public allocation patterns.)
The database is embedded in the program. Specifically, it is this file:
https://github.com/h2337/connmap/blob/master/connmap/resourc...
Presumably generated by the author with this Python script
https://github.com/h2337/connmap/blob/master/tools/get-ip-da...