The observability and estimability of collaborative opportunisticnavigation (COpNav) environments are studied.A COpNav environment can be thought of as a radio frequencysignal landscape within which one or more radiofrequency receiver locate themselves in space and time byextracting and possibly sharing information from ambientsignals of opportunity (SOPs). Available SOPs mayhave a fully-known, partially-known, or unknown characterization.In the present work, the receivers are assumedto draw only pseudorange-type measurements from theSOPs. Separate observations are fused to produce an estimateof each receiver’s position, velocity, and time (PVT).Since not all SOP states in the COpNav environment maybe known a priori, the receivers must estimate the unknownSOP states of interest simultaneously with theirown PVT. This paper establishes the minimal conditionsunder which a COpNav environment consisting of multiplereceivers and multiple SOPs is completely observable.In scenarios where the COpNav environment is not completelyobservable, the observable states, if any, are specified.Moreover, for the completely observable scenarios,the degree of observability, commonly referred to as estimability,of the various states is studied, with particularattention paid to the states with exceptionally good andpoor observability.
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