Realistic GPS Sensor Degradation

[andrewjong]

Is your feature request related to a problem? Please describe.

• desire to integrate MACVIO/MAC-SLAM with realistic usage
• currently we're not doing super realistic state estimation, it's coming from mavros sim with simulated sensors. see px4_mavlink_backend.py. The default multirotor uses default simulated sensors including barometer, imu, magnotometer, gps. The GPS sensor for example doesn't degrade based on environment occlusions
• therefore currently the simulator won't accurately reflect performance in GPS-degraded environments

Describe the solution you'd like

• support shadow interference, multicast interference, jamming
• apparently there is some research on how to simulate this: https://arc.aiaa.org/doi/full/10.2514/6.2023-2648
• The papers seem to line up nicely with that overall design, the first two papers seem to be a good fit for simulating a realistic GPS degradation scenario:
  • Cuenca et al. is the strongest reference for modeling degradation as an environmental effect driven by obstruction, shadowing, and satellite geometry / DOP rather than a binary outage.
  • Pant et al. feels like the most implementation-friendly starting point on the simulator side since it shows a practical real-time plugin approach using ray tracing in an urban environment.
• immediate deliverable have in mind is an environment-aware degraded GPS path for Isaac Sim / Pegasus, plus a clean way to test open-sky, degraded, denied, and recovery transitions against MACVIO

Additional context

• need for DTC, DSTA, Shimizu projects. Anything outdoors with GPS degradation