A receiver receiving global positioning data from one or more satellites above the Earth's surface detects a change in at least one parameter associated with the receiver and determines if the change is to be treated as erroneous. As a result of determining if the change in the at least one parameter is to be treated as erroneous, a further action may be performed. Determining if the change is to be treated as erroneous may include, for example, detecting changes in more than one parameter and determining if the changes are coincident. Detecting the change may also enable the receiver to predict the presence and magnitude of multipath components of signals, predict changes in an environment local to the receiver, predict large errors in position estimates determined by the receiver and modify an acquisition and tracking strategy used by the receiver.