We are witnessing continued improvements in wireless communications and geo-positioning. In addition, the performance/price ratio for consumer electronics continues to improve. These developments pave the way to a kind of location-based service that relies on the tracking of the continuously changing positions of the entire population of service users. This type of service is characterized by large volumes of updates, giving prominence to techniques for location representation and update. In this paper, we present several representations, along with associated update techniques, that predict the future positions of moving objects. For all representations, the predicted position of a moving object is updated whenever the deviation between it and the actual position of the object exceeds a given threshold. For the case where the road network, in which the object is moving, is known, we propose a so-called segment-based policy that represents and predicts an object's movement according to the road's shape. Map matching is used for determining the road on which an object is moving. Empirical performance studies and comparisons of the proposed techniques based on a real road network and GPS logs from cars are reported.