Traditional “low-to-high waveform change” timing markers, in navigation or GPS signals, can be easily naturally or maliciously altered and require unshareable, high-resolution, high-capacity channels, often not government available. Whereas, message text format methods include proven error correction, redundancy, encryption, jam-resistance, concealability, spoof-resistance, multiuser, delayable messaging, channel efficiency, and downstream authentication. Herein, “virtual timing markers” exploit message format strengths and more. Because many navigating platforms also communicate voice, messages, or data, platforms and multiuser messages can simultaneously and unintrusively share the same transmission signal, which reduces onboard hardware, needed channel capacity, radio frequencies, costs, and infrastructure. FAA mandated, airliner collision avoidance broadcasts of their GPS location can unintrusively commingle navigation messages with aforementioned strengths as precise derivative GPS timing markers on existing, prolific broadcasts having 1000× greater power levels. “Relayed transmission pathways” can eliminate cumbersome traditional nanosecond synchronization of navigation transmitters or exploit inclusion of happenstance neighborhood transmitters. Additional features.