Commodity Hubs are usually small areas, where the delivery of a trading standard has to take place. An example is the WTI crude oil contract (to be delivered in Cushing/Oklahoma).
But the concept can be generalized to wide spatial areas, if the ratio of transport costs to varioius areas from the source of the commodity is stable. It requires then, that the trading standard contract defines
these ratios and that the price of the commoditiy depends where it is finally delivered...