| 摘要 |
A system for determining the location of a moving signal-receiving station, when the primary location determination (LD) signals become unavailable because the antenna is adjacent to or within a signal-interfering structure, such as an urban canyon, a natural canyon, a forest or the like. Before the primary LD signals become unavailable, secondary LD signals are received at spaced apart locations and used to estimate the secondary LD signal source locations (preferably fixed). After the primary LD signals become unavailable, secondary LD signals, now with known source locations, are received and used, either alone or in combination with the remaining primary LD signals, if any, to determine the present location of the moving station. The primary LD signal sources can be GPS or GLONASS or LEO or other satellite-based sources. The secondary LD signal sources can be pseudolites or Loran signal towers or other ground-based sources.
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