They really don't explain the difference well. AIS is a local broadcast. It's like having a number plate that's visible from 10 miles away. VMS is 'phone hom

They really don't explain the difference well. AIS is a local broadcast. It's like having a number plate that's visible from 10 miles away. VMS is 'phone home' system. It's like having a gps tracker with cellular connectivity on your car, reporting into a federal agency (not hyperbole, that's the design goal.)