There was a great talk at the Chaos Computer Conference a few years ago how to diy this, sadly cant find it because web search seems dead nowaydays. If anyone knows, please chip in. It was a german researcher following german politicians who hilariously(scandalously?) related travel patterns
https://arstechnica.com/cars/2024/12/whistleblower-finds-une...
https://www.youtube.com/watch?v=iHsz6jzjbRc