What's the difference between DATS and DOA?

The difference to me is, I've spent my whole life in the U.S. and have never heard "DATS." The term "DOA" is quite common and, I suspect, known by virtually everyone here.

They’re the same

I believe that DATS means they died prior to being in the ambulance or being seen by first responders. Dead at the scene of the incident. DOA is someone who was alive but passed on the way to the hospital. First responders had vital signs but were not able to sustain them so the patient was dead on arrival to the hospital.