Both options are possible
I think to show the current position on the map, this is by far the easiest one:
AAdd the current lattitute & longitude to the car entity as attributes. When the current position changes just update the attributes and refresh the page.
If you are also interessted in the history of the location of the car, a location entity can be handy. By associating this to the car entity( 1 car has * locations) you can build up a history. Every time there is a new location, a new location object is created with a lattitude & longitude. Only thing is you need to find a way to plot this on the map , either by also having a current lattitude & longitdue on the car entity or by marking a location entity as current for example.