摘要：GPS clearly dominates the current market in positioning and navigation (POS/NAV). Besides being globally available, it provides the whole range of navigation accuracies at very low cost. GPS is also highly portable, has low power consumption, and is well suited for integration with other sensors, communication links, and databases.
At this point in the development of navigation technology, the need for alternative positioning systems only arises because GPS does not work in all environments. Current GPS receiver chips are reaching a unit price of about $5, and the predictions are that this figure will drop to about $1 when, most likely, it will level off.
