This paper discusses the design, development, and initial testing of a distributed monitoring system intended to detect and localize sources of harmful interference impacting Global Navigation Satellite System (GNSS) users over city sized areas using only a small number of monitoring stations to limit cost. The motivation and background of the work is rooted in the results of the Advanced Radio Frequency Interference Detection Analysis and Alerting System (ARFIDAAS), a network of GNSS Radio Frequency Interference (RFI) monitors which built the largest known database of multi-frequency GNSS RFI events. Insights gained from this database on parameters such as modulations, impacted bands, power-level distributions and other relevant factors are used to inform the design of the source localization system discussed in the paper.

The design of the receiver hardware to allow implementation of a distributed Time Difference of Arrival (TDOA) detection and localization system incorporating components of Commercial Off-The-Shelf (COTS) radios while supporting dynamic coverage of all L-band signals is detailed along with the software architecture used to control and operate the individual nodes of the work in progress development systems and testbed. Further information is included to describe the design and operation of the software which controls the composite network, including decisions made for the support of mobile detectors and multiple data consumers to allow pursuit of multiple simultaneous sources. Since the system is designed for detection of sources which are likely below the local noise floor at the participating nodes, the paper explores the derived operating envelope of the architecture, show examples of measurements produced during controlled field testing at Jammertest 2023, and discusses considerations for the screening of nuisance events likely to be unintentionally generated by incidental devices over a city sized area.