GPS Module

🟢 Start — zero knowledge, plain words. 🟡 Hands-on — building or buying, specifics and tradeoffs. 🔴 Specialist — the physics and math behind it.

🟢 Start. GPS adds speed, distance and a home arrow to your OSD — and above all it enables Rescue Mode: after signal loss the drone flies itself back toward the launch point. For long range it's not an option, it's an insurance policy.

🟡 Hands-on. Buy M10-generation modules, mount with a clear sky view, away from power wiring and the VTX (interference can kill the fix). Before arming, wait for a sensible satellite count and low HDOP (a geometry-quality metric — lower is better). In Betaflight, GPS Rescue works without a compass (it corrects course while moving); INAV/ArduPilot prefer a magnetometer for full navigation. And the iron rule: test rescue deliberately (switch off the radio at altitude, over an open field) before you trust it in a crisis.

🔴 Specialist. A GNSS receiver measures the arrival times of satellite signals; each time difference defines a sphere, and the intersection of ≥4 spheres yields position (and time). HDOP is precisely the conditioning of that geometry. The autopilot never uses raw GPS: it fuses it with the barometer and IMU in a filter (complementary/EKF), because GPS is slow and jumpy while baro drifts with weather — together they beat either alone. Rescue logic is a state machine: climb → return → descend → land/hover, with thresholds set by parameters — read all of them before you rely on them.

⚠️ Common mistakes: GPS zip-tied to the power harness; rescue "configured" but never tested.

🖼️ Photos: your own GPS module mount with clear sky view; a screenshot of satellite count and HDOP in the OSD/configurator.