What I’ve learned on COPS is what “get on the ground” means to cops. Before watching the show, from a standing position I would have replied, with a confused look on my face, “ahh ... I’m already on the ground” to that command.
When the police are yelling, “GET ON THE GROUND,” it’s actually only a suggestion. You can stand, sit, dance, run, whatever you like. And the cops won’t mind.