The Radar Fallacy

So, I mentioned The Octonauts in a previous post and I still think it is brilliant however there is another scientific flaw I have noticed. The Octopod’s Radar system seems to have the tv / film fallacy (it’s not a real fallacy, I made it up).
When a radar turns it discovers the position, as a distance and direction, from the radar. There are many types but they all work roughly the same. For a radar system to update the position of an object it must turn through the space where that object is. The radar sweep line on the Octonauts display turns at about 30 rpm meaning that the position of the decorator crab would jump every 2 seconds as it gets scanned. However, the position of the crab as marked by the blip on the screen moves smoothly even while the radar sweep is well away from the crab. This could, of course, be because of an auxiliary system that is not mentioned in the show.
I am sure there are films and tv shows where the radar has a finite refresh time but the movement of planes are smooth. Time to start looking at radar shots more closely!