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telemetry

GPS Analysis from First Airborne ET Flight

Overview

I wanted to share some very interesting GPS data collected during the first flight of an Extended Telemetry UserDefind message set carrying GPS stats.

The results challenge some of my established beliefs about GPS performance relating to lock time. Some more epxeriments will shed more light on this.

The results have provided new insight and evidence into an ongoing mystery about why my tracker almost always has a 1-hour blackout period on initial launch before transmissions are received.

Major Takeaway Summary

Summary

  • The GPS appears to have a huge problem with getting locks while rising
    • Compared to, say, staying at ground level, or floating at altitude
    • Not seemingly correlated with ground speed
  • There is approximately a 1 hour period of time from launch in my area (NYC area) to first transmission, seemingly due to GPS inability to get a lock
  • The number of Chinese GPS satellites visible in flight rises significantly during flight

Telemetry's Future

Overview

Common telemetry questions:

  • Where is telemetry documented? (For implementation or curiosity)
  • Can telemetry be extended? And to what?
    • Who decides these things?

This change aims to answer those questions and provide a path forward.

Short answer -- it's documented here, we can extend it, and we all get to decide how.