They don’t work that way. They subtract the speed of the police vehicle from the speed captured. I know because they caught me in Ohio once, and he had my exact speed. I laughed & said I had no clue you could clock me coming at me. He laughed & explained how it works now.
“Rolling Radar” I’ve e heard it called.
So when was the police car speedo calibrated and what are the certification records of the technician....?