# autopilot — Glossary

**Status**: confirmed-by-user (2026-05-17), updated for the rewrite paradigm.

Project-specific terms only. Generic CS / industry terms (RTSP, gRPC, FastAPI, MAVLink, JSON, etc.) are intentionally omitted.

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**AUTO mode** — fixed-wing autopilot flight mode in which the airframe follows its uploaded mission. `mission_executor`'s fixed-wing variant uploads the mission and waits for the operator to switch the airframe into AUTO via RC; only then does it transition to `FLY_MISSION`. source: `architecture.md §7.7`.

**Behaviour tree (BT)** — hierarchical decision-making model (Selector / Sequence / Condition / Action / Decorator) ticked from the root every cycle. The canonical decomposition of `scan_controller`'s logic. The implementation may use a typed deterministic state machine that satisfies the same priorities, preemption, and tick scenarios. source: `system-flows.md §F4`.

**Benchmark gate** — proof-of-concept milestone. Tier 1 ≤100 ms/frame, Tier 2 ≤200 ms/ROI, VLM ≤5 s/ROI, A40 transition ≤2 s, decision-to-movement ≤500 ms, ≤5 POIs/min. Must pass before product code begins. source: `architecture.md §7.6 Benchmark gate`.

**`../detections`** — separate sibling repo. FastAPI / Cython service running TensorRT YOLO26 + YOLOE-26 FP16 engines. Tier 1 primitive detection lives here, NOT in autopilot. Consumed by `detection_client` over bi-directional gRPC. source: `architecture.md §1`, `../_docs/03_detections.md`.

**detection_client** — autopilot component: bi-directional gRPC client to `../detections`; streams frames out, receives bounding boxes back; same bboxes are reused for Tier 2 ROI selection and for operator overlay. source: `components/detection_client/description.md`.

**Confidence-scaled timeout** — operator-decision window scales linearly with target confidence: 40 % → 30 s, 100 % → 120 s. Below 40 % a target is not surfaced. Timeout = forget; decline = `IgnoredItem` entry. source: `architecture.md §5 Architectural Principles`.

**Ego-motion compensation** — separating target motion from platform motion in `movement_detector`, using synchronised video + gimbal angle + zoom state + UAV telemetry. Naive frame-differencing is explicitly rejected. Per-zoom-band thresholds: tighter at zoom-in. source: `architecture.md §5 Architectural Principles`, `components/movement_detector/description.md`.

**Flight-gate** — suite-wide convention: a marker file (`/run/azaion/in-flight`) written by autopilot at startup and removed at shutdown, read by `model-sync.service` to defer model swaps during flight. source: `../_docs/00_top_level_architecture.md`, `deployment/containerization.md §3`.

**frame_ingest** — autopilot component: pulls RTSP from ViewPro A40, decodes, timestamps, hands frames to `detection_client`, `movement_detector`, and `telemetry_stream`. source: `components/frame_ingest/description.md`.

**Geofence (INCLUSION / EXCLUSION)** — polygonal area constraint in the mission. **Both** are enforced symmetrically in the rewrite (`mission_executor`); a violation triggers RTL. source: `architecture.md §5 Architectural Principles`, `§7.7 MAVLink and Piloting`, `components/mission_executor/description.md`.

**gimbal_controller** — autopilot component: ViewPro A40 control protocol (yaw / pitch / zoom) + zoom-out sweep + zoom-in path-follow + target-follow centre-window. source: `components/gimbal_controller/description.md`.

**Ground Station API** — external, out-of-this-repo service that receives a continuous camera + telemetry stream from each UAV and hosts the operator browser UI (bbox overlay, target confirm/decline). Not built; not in autopilot scope. source: `architecture.md §1`, `../_docs/04_system_design_clarifications.md`.

**Hand-rolled MAVLink layer** — `mavlink_layer` implements the ~10–15 MAVLink commands this codebase actually uses with no third-party SDK. Eliminates the largest dependency-risk item. source: `architecture.md §7.7`, `components/mavlink_layer/description.md`.

**H3 spatial index** — hexagonal hierarchical geospatial indexing used by `mapobjects_store` for fast new / moved / existing / removed diffs. source: `architecture.md §7.9`, `components/mapobjects_store/description.md`.

**IgnoredItem** — operator-declined target. Persisted in `mapobjects_store` as `(MGRS, class_group)`; new detections matching an entry are suppressed before reaching the operator. source: `architecture.md §7.12`, `components/mapobjects_store/description.md`, `data_model.md §IgnoredItem`.

**Jetson Orin Nano** — edge-device compute platform (NVIDIA, aarch64, CUDA-capable). 8 GB shared LPDDR5; ~2 GB used by Tier 1, ~6 GB available for the rest of autopilot + VLM. source: `architecture.md §7.3`.

**Zoom-out / zoom-in scan** — two-tier search behaviour. **Zoom-out level** = wide / light-medium zoom sweep along the UAV route, runs `movement_detector` + Tier 1. **Zoom-in level** = zoom into a queued POI for Tier 2 ROI analysis + optional VLM confirmation; `movement_detector` continues to run with per-zoom-band thresholds. State-machine variants: `ZoomedOut`, `ZoomedIn { roi, hold_started_at }`. source: `architecture.md §7.1`, `components/scan_controller/description.md`.

**MapObject** — entry in `mapobjects_store`; keyed by `H3_cell + class`; carries GPS, size, class, and a list of recent observations. source: `architecture.md §7.9`, `data_model.md §MapObject`.

**mapobjects_store** — autopilot component: on-device H3-indexed map of detected objects + ignored-items list. No REST API. source: `components/mapobjects_store/description.md`.

**mavlink_layer** — autopilot component: hand-rolled MAVLink v2 transport + the small command set this codebase needs. source: `components/mavlink_layer/description.md`.

**MGRS** — Military Grid Reference System; primary coordinate encoding for autopilot ⇄ operator sync messages and for `mapobjects_store` keys. source: `architecture.md §7.10`, `data_model.md §MGRS sync message`.

**Middle waypoint** — autopilot-inserted waypoint between the current position and the next mission waypoint, computed from an operator-confirmed POI. Triggers a mission re-upload (`MISSION_CLEAR_ALL` + standard upload sequence). source: `architecture.md §7.7`, `components/mission_executor/description.md`.

**mission_client** — autopilot component: pulls the mission from the `missions` API on start; POSTs middle-waypoint inserts; honours the mission cascade signal. source: `components/mission_client/description.md`.

**mission_executor** — autopilot component: variant-specific (multirotor / fixed-wing) state machine that drives the airframe through connect → health-check → arm/takeoff (multirotor) or wait-for-AUTO (fixed-wing) → upload → fly → land. Owns geofence enforcement. source: `architecture.md §7.7`, `components/mission_executor/description.md`.

**mission-schema** — shared schema artefact between `autopilot` and `missions` repos. Extraction location TBD (`_infra/` at suite root, or a small third repo) — `architecture.md §8 Q5`. source: `architecture.md §5`.

**`missions`** — separate sibling repo (.NET service). Hosts the missions REST API. Stays separate from `autopilot`; the two share `mission-schema`. source: `../_docs/02_missions.md`.

**Movement candidate** — small moving point/cluster emitted by `movement_detector` in either zoom-out or zoom-in. Tagged with `source_zoom_band`. Promoted to a zoom-in POI by `scan_controller` (or used to bump in-progress ROI confidence at zoom-in). source: `architecture.md §7.4`, `data_model.md §MovementCandidate`.

**movement_detector** — autopilot component: OpenCV optical-flow / global-motion estimation with mandatory ego-motion compensation. Active at **both** zoom-out and zoom-in (suppressed only during target-follow); per-zoom-band thresholds. Classical-CV adequacy at zoom-in is benchmark-gated; learned-CV fallback per Q14. source: `components/movement_detector/description.md`.

**operator_bridge** — autopilot component: surfaces POIs (via `telemetry_stream` → Ground Station) for operator confirm / decline; forwards target-follow start / release; on decline appends an `IgnoredItem`. source: `components/operator_bridge/description.md`.

**Optionality model (VLM)** — VLM is the only optional Tier. Two complementary mechanisms: a runtime `vlm_enabled` flag, and a build-time feature module. The system MUST function correctly with VLM absent. source: `architecture.md §7.6 Local VLM confirmation > Optionality model`, `components/vlm_client/description.md §9`.

**POI (Point of Interest)** — a queued candidate for zoom-in inspection (footpath start, branch pile, tree row, movement candidate, etc.). source: `architecture.md §7.1`, `data_model.md §POI`.

**POI queue** — operator-review queue inside `scan_controller`; ordered by `confidence × proximity × age_factor`; hard cap of **≤5 POIs/min** to bound operator workload. source: `architecture.md §5`, `components/scan_controller/description.md`.

**RTL (Return-to-Launch)** — MAVLink-driven return to the configured rally point; triggered by INCLUSION / EXCLUSION violation, by max-retry exhaustion in `mission_executor`, or by failsafe in the autopilot itself. source: `architecture.md §7.7`, `components/mission_executor/description.md`.

**Scan controller** — autopilot component: central deterministic typed state machine — `ZoomedOut`, `ZoomedIn`, `TargetFollow`. Owns POI queue, timeouts, gimbal commands, ≤5 POIs/min cap. source: `architecture.md §7.6 Scan controller and POI queue`, `components/scan_controller/description.md` (full BT spec in `system-flows.md §F4`).

**semantic_analyzer** — autopilot component (Tier 2): primitive graph + lightweight ROI CNN, reasoning over paths, branch piles, dark entrances, etc. source: `components/semantic_analyzer/description.md`.

**SITL conformance gate** — CI stage in which autopilot runs against ArduPilot SITL with a mocked `../detections` and a fixture mission, asserting the MAVLink command surface and geofence enforcement. source: `deployment/ci_cd_pipeline.md §5`.

**Sweep** — zoom-out camera motion: gimbal swings left-right across the UAV's flight path while the UAV flies the mission. Exact pattern (pendulum / raster / lawn-mower), FOV per zoom tier, dwell time, and mission-segment alignment are unresolved (`architecture.md §8 Q1`). source: `architecture.md §7.1`, `components/gimbal_controller/description.md`.

**Target-follow mode** — gimbal keeps an operator-confirmed target centred (within the centre 25 % of frame) while the UAV continues to move. Ends on operator release or tracking loss. State-machine variant: `TargetFollow { target_id, started_at }`. source: `architecture.md §7.1`, `components/scan_controller/description.md`.

**telemetry_stream** — autopilot component: continuous (always-on) push of camera frames + flight telemetry + bbox overlay over modem to the Ground Station API. Operator always sees live feed, not just on detection. Carries operator commands on the return path. source: `components/telemetry_stream/description.md`.

**Tier 1 detection** — primitive YOLO over the full frame; delegated to `../detections`. source: `architecture.md §7.6 Tier 1 primitive detector`.

**Tier 2 semantic** — primitive-graph + lightweight ROI CNN reasoning over zoom-in crops; lives in autopilot. source: `architecture.md §7.6 Tier 2 semantic analyzer`.

**Tier 3 / VLM (Vision Language Model)** — NanoLLM running VILA1.5-3B in a separate local process, invoked only for bounded zoom-in ROI confirmation. Local IPC over Unix domain socket with peer-credential check. No cloud egress. Optional. source: `architecture.md §7.6 Local VLM confirmation`, `components/vlm_client/description.md`, `system-flows.md §F3`.

**vlm_client** — autopilot component: optional local-IPC client to a NanoLLM/VILA1.5-3B process; validates ROI payload, calls VLM, validates response against the `VlmAssessment` schema. source: `components/vlm_client/description.md`.

**VlmAssessment** — structured-schema output from the VLM. The free-form VLM text is not a downstream API contract. source: `architecture.md §5 Architectural Principles`, `data_model.md §VlmAssessment`.

**ViewPro A40** — deployment gimbal hardware. NFR budget: zoom transition ≤2 s, decision-to-movement ≤500 ms. source: `architecture.md §7.3`, `components/gimbal_controller/description.md`.

**Waypoint** — mission node coordinate (lat, lon, alt). Pulled from the `missions` API by `mission_client`; the operator-confirm flow may insert a **middle waypoint** to detour toward a confirmed target. source: `architecture.md §7.7`, `data_model.md §MissionWaypoint`.

**BIT (Built-In Self Test)** — pre-flight gate run by `mission_executor`. Covers GPS lock, camera RTSP, gimbal homing, `../detections`, VLM warmup (if enabled), mission load, MapObjects pre-flight pull, persistent-store free space, wall-clock binding, MAVLink + airframe health. Items return `OK | DEGRADED | FAIL`. DEGRADED requires signed operator acknowledgement. FAIL blocks transition past `HEALTH_OK`. source: `architecture.md §5 / §7.3`, `system-flows.md §F9`.

**Lost-link failsafe ladder** — typed ladder evaluated each tick by `mission_executor` against the operator/Ground-Station modem heartbeat: `LinkOk` (≤5 s) → `LinkDegraded` (≤30 s, queue events, health yellow) → `LinkLost` (>30 s, no follow) → `LinkLostInFollow` (>30 s in target-follow, +30 s grace). Default action on lost link is RTL. MAVLink-link loss to ArduPilot itself is a separate, more severe event. source: `architecture.md §5 / §7.7`, `system-flows.md §F10`.

**MapObjects sync** — pre-flight pull + post-flight push of MapObjects + IgnoredItems against the central `missions` API extension `/missions/{id}/mapobjects`. In-flight is batched only (no streaming over modem). On-device store is a working copy; central store is the source of truth across missions. source: `architecture.md §5 / §7.13`, `system-flows.md §F8`, `components/mapobjects_store/description.md`, `components/mission_client/description.md`.

**Per-zoom-band thresholds** — `movement_detector` configuration is split between zoom-out and zoom-in because the pixel-to-metre ratio differs by ~10×. Cluster persistence threshold, residual-velocity floor, telemetry-skew tolerance, and enqueue-latency budget are all per-band. source: `architecture.md §7.6 Movement detector`, `components/movement_detector/description.md §5`.

**Operator-command authentication** — every operator command (confirm / decline / target-follow / safety-override / BIT-degraded-acknowledge) carries a session-bound signature with replay protection, validated by `operator_bridge` before dispatch. The principle is committed; the exact scheme is open per Q9. source: `architecture.md §5 / §8 Q9`, `components/operator_bridge/description.md`.

**Sync state (`mapobjects_store`)** — `synced | cached_fallback | degraded`. `synced` after a fresh successful pull or a successful post-flight push. `cached_fallback` when pre-flight pull failed and the operator acknowledged continuing on cache. `degraded` after a persistent push failure or a stale cache. `scan_controller` suppresses MapObject diff classifications while `degraded` to avoid corrupting the central observation log. source: `components/mapobjects_store/description.md §5`.

**Wall-clock source** — autopilot binds wall-clock to GPS time once GPS is locked (preferred) or to NTP at boot if reachable. Drift > 200 ms surfaces health → yellow. Monotonic clock (independent of wall-clock) is authoritative for telemetry-skew compensation and tick budgets. source: `architecture.md §7.3 Reliability and safety`.
