Services Using com.apple.geod
Making an exhaustive list of all processes that call a specific API or process would be technically challenging even for one single release point of MacOS. You would either need access to the source code of all of MacOS and every single app - both first party and third party - or you would need to debug/reverse engineer all processes as they run and expose those calls.

The application Little Snitch does that for the network stack - so you might have better luck just blocking network access to Apple servers rather than trying to block the calls to the service locally.

Even if you were to process all the geo location aspects on developer.apple.com - it's widely used - far greater than just the Core Location API - https://developer.apple.com/documentation/corelocation.


Weather
Calendar
Address Book
Maps
Siri
iCloud (finding the best data center to route uploads)
Store (which geographic region should your content be)
Time Zone and Night Shift
Safari location