A system to select one or more types of satellites from a plurality of types of satellites in a multi-constellation of satellites, the system comprising: a plurality of receivers 121-123 including at least: a first receiver configured to input signals from a first type of satellite; and a second receiver configured to input signals from a second type of satellite; a processor configured to: execute a multi-constellation-selection software module to: associate a current position with a mapping feature, wherein mapping features include at least one of: a plurality of grid points that span the earth; a plurality of complex polygons that span the earth; and a plurality of combinations of complex polygons that span the earth and grid points that span the earth; and to select at least one type of satellite from the plurality of types of satellites based on the associated mapping feature (GP, CP); the processor further configured to execute a compute-position/velocity/time software module in order to compute the current position, a current velocity, and a current time based on at least one selected input signal input at a receiver associated with the at least one selected type of satellite, wherein signals from satellites of none selected type are not passed to the compute-position/velocity/time software module; and feed-back the computed current position, the current velocity, and the current time to the multi-constellation-selection software module based on the execution of the compute-PVT software module to implement rules for selecting the at least one type of satellite. a plurality of receivers 121-123 including at least: a first receiver configured to input signals from a first type of satellite; and a second receiver configured to input signals from a second type of satellite; a first receiver configured to input signals from a first type of satellite; and a second receiver configured to input signals from a second type of satellite; a processor configured to: execute a multi-constellation-selection software module to: associate a current position with a mapping feature, wherein mapping features include at least one of: a plurality of grid points that span the earth; a plurality of complex polygons that span the earth; and a plurality of combinations of complex polygons that span the earth and grid points that span the earth; and to select at least one type of satellite from the plurality of types of satellites based on the associated mapping feature (GP, CP); the processor further configured to execute a compute-position/velocity/time software module in order to compute the current position, a current velocity, and a current time based on at least one selected input signal input at a receiver associated with the at least one selected type of satellite, wherein signals from satellites of none selected type are not passed to the compute-position/velocity/time software module; and feed-back the computed current position, the current velocity, and the current time to the multi-constellation-selection software module based on the execution of the compute-PVT software module to implement rules for selecting the at least one type of satellite. associate a current position with a mapping feature, wherein mapping features include at least one of: a plurality of grid points that span the earth; a plurality of complex polygons that span the earth; and a plurality of combinations of complex polygons that span the earth and grid points that span the earth; and to select at least one type of satellite from the plurality of types of satellites based on the associated mapping feature (GP, CP); the processor further configured to execute a compute-position/velocity/time software module in order to compute the current position, a current velocity, and a current time based on at least one selected input signal input at a receiver associated with the at least one selected type of satellite, wherein signals from satellites of none selected type are not passed to the compute-position/velocity/time software module; and feed-back the computed current position, the current velocity, and the current time to the multi-constellation-selection software module based on the execution of the compute-PVT software module to implement rules for selecting the at least one type of satellite.