What has changed
The platform has changed from Raspberry PI to Windows Server. I have a Windows server providing services in my LAN network. It spends most of its time doing nothing much. Thus the challenge to run the virtual radar as a native Windows service.
The source code needed to be ported from Linux based to Windows C toolchain. By this time I was working with Visual Studio 2017. There were plenty of challenges, for one I hadn't touched C for a very long time. Then native C in windows is not threading, but the virtual radar code needs it to be, and I had no want to refactor it all. This is when cross platform (yes, I am sometimes a slow learner) opened up to me. And this was just the start.
Cartography and Mapping needed replacement as Google maps is no longer usable for small non-commercial free applications and now requires compulsory access to your bank account. As I have worked with many other projects that interactively work with OpenStreetMaps, the choice was easily made. Do note that even though OSM is 'free', users of this system are required to contribute back by adding or keeping exisiting data updated.
All geographical calculations, like the distance (as the crow flies) between two co-ordinates had to be researched and programmed (Haversine formula), as previously the Google Maps libraries were used for these types of services, needed to be understood,coded and 'owned' as local accessable and managable code base. Tip to self: Beware! Maybe advise others and also look into CDN's, I expect that to go the same way soon as well or at least at a cost.