Thanks for the info. I only know what I read in that article at F1techI hope you realise how long it takes for a bulk carrier to stop or change course. Ships are tracked far more aggressively then you might think. Its very important for incident investigation to know exact times when changes occur because it takes so long for it to have a visible effect. AIS for example can be sub 2 seconds.
Polling intervals aren't a factor for accuracy sure the exact deployments used for VTS might not fit F1 but that has nothing to do with what makes DGPS so accurate. when your cars are what 1.8 meters by 4-5 meters (?) 1meter accuracy doesn't seems that good.