Abstract: The present invention is related to location positioning systems, and more particularly, to a method and apparatus for making accuracy improvements to a GPS receiver's navigation calculations. According to a first aspect, the invention includes maintaining a table of height attributes for major cities and urban areas around the world (contour table) in the GNSS chipset. The information in the table preferably includes latitude, longitude of the city along with height attributes of those cities, such as the average, min, max height and region boundary etc. Additional information such as average gradient could also be saved in the table. According to further aspects, when GPS signals are degraded in environments such as urban canyons, the height information can be obtained from the table and used to improve the navigation solution.

Abstract: The present invention is related to location positioning systems, and more particularly, to a method and apparatus for making accuracy improvements to a GPS receiver's navigation calculations. According to a first aspect, the invention includes maintaining a table of height attributes for major cities and urban areas around the world (contour table) in the GNSS chipset. The information in the table preferably includes latitude, longitude of the city along with height attributes of those cities, such as the average, min, max height and region boundary etc. Additional information such as average gradient could also be saved in the table. According to further aspects, when GPS signals are degraded in environments such as urban canyons, the height information can be obtained from the table and used to improve the navigation solution.

Abstract: A method for improving fault detection and exclusion of a GPS receiver is provided. The method determines pseudorange measurement residuals of tracked signals, divides the signals into two groups based on whether each signal has a higher or lower probability of being a failure, and estimates a residual bias using only the lower probability group of signals. The method further removes the residual bias from all calculated residuals, and compares each range residual to one of three different thresholds. A tighter threshold is applied to positive residuals of the group of signals with higher failure probability than to the group of signals with lower failure probability. A further tighter threshold is applied to negative residuals of the group of signals having higher failure probability. The method then determines PVT values of the GPS receiver utilizing range measurements of signals whose measurement residual magnitudes are less than their corresponding threshold values.

Abstract: A method for improving fault detection and exclusion of a GPS receiver is provided. The method determines pseudorange measurement residuals of tracked signals, divides the signals into two groups based on whether each signal has a higher or lower probability of being a failure, and estimates a residual bias using only the lower probability group of signals. The method further removes the residual bias from all calculated residuals, and compares each range residual to one of three different thresholds. A tighter threshold is applied to positive residuals of the group of signals with higher failure probability than to the group of signals with lower failure probability. A further tighter threshold is applied to negative residuals of the group of signals having higher failure probability. The method then determines PVT values of the GPS receiver utilizing range measurements of signals whose measurement residual magnitudes are less than their corresponding threshold values.