Navigation systems, such as satellite navigation systems, are commonly used by a variety of different users to determine a general location of the user, to determine a route to a destination location, and/or to navigate to that destination location. One example of a navigation system uses a global navigation satellite system (GNSS), such as the Global Positioning System (GPS), and receives satellite signals broadcast from multiple satellites. Navigation systems often include navigation system receivers carried by a user or a vehicle as the user or Vehicle moves. The navigation system receivers receive navigation signals, process the navigation signals to obtain navigation data (e.g., estimated positions of the receiver), and provide navigation data and/or navigation instruction based on the navigation data. Navigation instruction may be provided by displaying the navigation route with an approximate receiver (i.e., user or vehicle) location on a map using a map application.
Achieving desired accuracy with navigation systems has been an ongoing challenge. The navigation data may include errors caused by various effects such as the effect of the atmosphere on the satellite signals, clock accuracy, and multipath errors caused by reflected satellite signals. Thus, the estimated positions of the navigation receiver, as determined from processing satellite signals and data, may vary from the actual absolute positions of the receiver as the receiver moves. The resulting track determined for the receiver from this noisy position stream can vary erratically and may appear to jitter when displayed on a map grid (e.g., streets and highways) even though the user or vehicle carrying the receiver may be traveling in a straight line. To improve performance and user experience, map applications used to display the approximate receiver location often correct or snap the approximate receiver location to the map grid based on the proximity of the estimated current position to the map grid.
Although snapping the approximate receiver location to a map grid may improve user experience, problems may occur when the discrepancy between the estimated position and the actual absolute position of the receiver is substantial (i.e., as a result of lower accuracy). When a user or vehicle approaches a waypoint, for example, and deviates from the established navigation route (e.g., takes a wrong turn), the lower accuracy may cause the system to have a substantial latency between the actual deviation from the route and the identification or detection of the deviation by the receiver. In particular, the map application may assume that the deviation of the estimated position from the navigation route is a result of an inaccurate position measurement and thus snap the receiver location to the grid along the navigation route as if the receiver is following the navigation route. The deviation may eventually be identified but the substantial delay in identifying the deviation caused by the lower accuracy often prevents the user or vehicle from making a correction in a timely manner, resulting in the calculation of a new navigation route or hindering the user experience.
Navigation system receivers may use various signal and data processing techniques to improve the accuracy of the estimated position of the receiver relative to an actual absolute position of the receiver. Signal and data processing techniques that improve accuracy, however, may also increase power consumption in the navigation system receiver. To operate with lower power consumption, which may be desirable in certain applications, may require a lower accuracy and may result in the problems identified above.