Abstract: 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.

Abstract: According to one embodiment, a slope of a land mass is precisely monitored. Remote sensors are placed in selected positions on the slope. The remote sensors are configured to provide real time position information. A virtual model of the slope is created using positioning information generated by the remote sensors and is stored in a computer memory. The position of each remote sensor is also recorded in the computer memory so that the virtual model accurately reflects the real world situation. A threshold value is set to establish a permissible deviation of each remote sensor location. Real time positioning information produced by the remote sensors is monitored at a base station and is used to update the virtual model. If the position of a remote sensor deviates beyond its associated threshold value, an alarm message is flashed. The information so obtained can also be displayed to a user as a graphical and textual representation of the current state of the slope.