Anti-jamming — keyed frequency hopping. The link splits its bandwidth into N discrete channels and both radios retune every hop interval T = 1/rate, following a sequence known only to them:
c(n) = PRNG(key, n) mod N — keyed, unpredictable
c(n) = n mod N — sequential, predictable
A jammer that cannot recover the key can only cover a fixed fraction ρ of the band at once ("partial-band jamming"). Since the drone's next channel is uniformly unpredictable, a hop is lost with probability ≈ ρ — the Jammer band coverage slider is exactly this ρ, and delivery settles near 1 − ρ. If the sequence is instead a plain counter, an adaptive "follower" jammer learns the pattern after a few hops and retunes onto the drone's next channel almost every time, driving delivery toward zero regardless of how narrow its band is. The security comes from the secrecy of the key, not from hopping itself. The waterfall panel makes this legible over time: each column is one hop, each row a channel — a keyed sequence scatters cyan hits across all 32 rows while the fixed red jam band stays put; a sequential run turns almost the whole track red as the follower locks on.
GPS spoofing detection — sensor cross-check. The drone keeps a second, independent position estimate from its IMU by dead reckoning:
x_ins(t) = x_ins(t-dt) + v(t)·dt (accelerometer + gyro integration)
d(t) = |x_gps(t) − x_ins(t)|
Under normal operation both estimates track the same truth and stay within sensor noise. A spoofer that broadcasts a stronger, fabricated GPS signal can drag the reported GPS fix away — but it cannot touch the IMU, which keeps dead-reckoning from the drone's true track. Once the divergence d(t) exceeds a threshold and stays there for a sustained interval (to reject a brief noise spike), the autopilot flags a spoofing alarm and falls back to INS-only navigation until GPS is trustworthy again. This is the same cross-check principle used in real GNSS-denial-resilient autopilots. Drag inside the map to pan and inspect the true track (cyan), the INS estimate (green) and the spoofed GPS fix (magenta) as they separate.