GPS signal availability in an urban area-receiver performance analysis

GPS signal availability and DGPS positioning accuracy for two-dimensional navigation in two types of urban area, namely a downtown type with buildings up to 50 stories, and a residential area with two-story housing and tree-lined streets, is investigated using three multi-channel C/A code receiver types, including a fast-reacquisition narrow correlator spacing receiver. Signal availability, defined as the percentage of time during which HDOP⩽5, is shown to be strongly dependent on the receiver signal tracking performance. Signal availability variations between receivers exceed 25% in some cases. The DGPS positions obtained with various receivers are intercompared and analysed as a function of satellite geometry and of the multipath environment. The narrow correlator spacing receiver is shown to produce superior positioning results, in terms of repeatability, as compared to the standard wide correlator spacing receivers used. Performance statistics based on repeated test runs are presented for the various scenarios described above