mirror of
https://github.com/azaion/gps-denied-onboard.git
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Oleksandr Bezdieniezhnykh
9eba1689b3
- Revised acceptance criteria in the acceptance_criteria.md file to clarify metrics and expectations, including updates to GPS accuracy and image processing quality. - Enhanced restrictions documentation to reflect operational parameters and constraints for UAV flights, including camera specifications and satellite imagery usage. - Added new research documents for acceptance criteria assessment and question decomposition to support ongoing project evaluation and decision-making.
59 lines
7.6 KiB
Markdown
59 lines
7.6 KiB
Markdown
# Restrictions
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> **Last revised**: 2026-04-26 (post Mode B Solution Assessment + user-driven addendum on camera spec & zoom level).
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## UAV & Flight
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- Photos are taken by airplane (fixed-wing) type UAVs only.
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- Photos are taken by the navigation camera pointing downwards and fixed (not gimbal-stabilized).
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- Operational area is the eastern and southern parts of Ukraine (east/left of the Dnipro River).
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- Mission profile: 8-hour flights at ~60 km/h cruise. Two route shapes coexist:
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- **Sector**: up to **10 × 15 km = 150 km²** of dense coverage.
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- **Transit corridor**: ~**50 km × 1 km = 50 km²** strip in/out of the sector.
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- **Total operational area: up to ~400 km²** of pre-cached satellite imagery per mission. Cache is **persistent across flights** (not redownloaded each mission). Storage budget **~10 GB** for the satellite tile cache; see AC-NEW-3 for flight-data-recorder budget.
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- Altitude: pre-defined, **≤1 km AGL**. Terrain is assumed flat (operational area is rolling steppe / agricultural land); height differences are negligible.
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- Weather: predominantly sunny daytime operations.
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- Sharp turns occur but are the exception, not the rule. Two consecutive photos may share <5% overlap during a turn (see AC-3.2).
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- **No photo-count cap.** The previously stated "up to 3000 photos per flight" was a legacy operator number from a Mavic-class workflow; it is dropped because (a) it is inconsistent with 8 h × 3 fps, and (b) the system does **not store raw photos at all** (see AC-8.5). Storage is bounded by the tile-cache + FDR caps (~10 GB persistent + 64 GB / flight, AC-NEW-3).
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## Cameras
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- The UAV carries **two cameras**:
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1. **Navigation camera** — fixed, downward-pointing, not autostabilized. Consumed by the GPS-Denied system for position estimation.
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2. **AI camera** — main mission camera with operator-controllable gimbal angle and zoom. Consumed by onboard AI detection systems.
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- **Navigation camera**: **ADTi 20MP 20L V1, APS-C sensor, ~5472 × 3648 px (≈20 MP)**. APS-C sensor (~23.6 × 15.7 mm). Lens TBD — selected during solution-draft phase to land GSD in the **10–20 cm/px band at 1 km AGL** (drives a frame ground footprint of ~470 m × 314 m to ~980 m × 655 m depending on focal length). Other intrinsics (focal length, exact sensor dimensions, distortion coefficients) are pinned at module-selection time and used by Component-1b orthorectification (pre-flight checkerboard calibration, F-F2).
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- **AI camera pose information available to the GPS-Denied system**: gimbal angle and zoom only. The UAV's instantaneous bank/pitch is **not** published from the autopilot to the AI-camera reasoning path. Object-localization accuracy is therefore scoped to level flight (AC-7.1).
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- Cameras connect to the companion computer over USB, MIPI-CSI, or GigE (specific interface TBD at solution-draft phase, dependent on chosen module).
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## Satellite Imagery
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- **Source: Azaion Suite Satellite Service** (a separate component of the wider Suite). The onboard system is a **consumer** of this service, not a direct customer of commercial providers. Upstream sourcing (Maxar / Airbus / partner agencies / commissioned tasking) is the Satellite Service's concern, not this build's.
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- **Onboard interface to the Service is offline-only**: the companion computer holds a local cache populated **before flight** by syncing from the Service for the operational area (AC-8.3). No satellite imagery is fetched in-flight from the Service.
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- **Mid-flight tile generation (AC-8.4)**: during the mission the companion computer generates fresh tiles from the navigation camera, orthorectified into the basemap projection, deduplicated against the existing cache, and stored locally. On landing, those new tiles are uploaded back to the Suite Satellite Service for ingestion, so the next mission's cache is refreshed by the previous flight.
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- **No raw photo storage** (AC-8.5): the tile is the unit of persistence. Raw nav-camera and AI-camera frames are not retained (except a low-rate failure-thumbnail log for forensics).
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- **Resolution at the cache interface**: 0.5 m/pixel minimum, 0.3 m/pixel ideal (AC-8.1). The architecture is provider-agnostic at the cache boundary; whatever the Suite Satellite Service supplies must meet that bar.
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- **Storage tile zoom level**: **slippy-XYZ z=20 (~30 cm/px, 512×512)** — pinned because the matcher (Component 3) needs ≤~4× scale ratio between the UAV frame (~12 cm/px GSD at 1 km AGL with the 20 MP APS-C camera) and the reference; z=20 gives a 2.5× ratio (workable), z=18 gives a 10× ratio (matcher accuracy breaks down). Storage budget at z=20 across the 400 km² operational area = ~2.8 GB cache + ~30 MB DEM + ~16 MB VPR chunk index ≈ ~3 GB total — well inside the 10 GB cache budget. **VPR retrieval unit is decoupled from the storage tile** (see AC-8.6 below): VPR chunks are derived from the z=20 tile cache at ground-footprint scale (~600–800 m chunks with 40–50 % overlap), independent of the storage zoom level.
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- **Freshness gates** (AC-8.2 / AC-NEW-6) are enforced at runtime: tiles older than 6 months (active-conflict sectors) or 12 months (stable rear sectors) are rejected or down-confidence-weighted. Tiles generated mid-flight are timestamped with the current flight date and treated as fresh.
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- **Free public imagery (Sentinel-2 etc.)** is not on the runtime path. If the Suite Satellite Service ever returns Sentinel-class tiles, the cache rejects them as below the 0.5 m/px floor.
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## Onboard Hardware
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- Processing platform: **Jetson Orin Nano Super** — 67 TOPS sparse INT8, **8 GB shared LPDDR5** (CPU and GPU share the same memory pool), **25 W TDP**.
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- Companion computer runs JetPack (Ubuntu-based) with CUDA / TensorRT available.
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- Sustained GPU load may cause thermal throttling; the processing pipeline must stay within the thermal envelope. The cooling solution shall sustain the 25 W power mode for the 8-hour duty cycle at the upper environmental-envelope temperature (AC-NEW-5).
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- Onboard non-volatile storage: budget at least the satellite-cache (~10 GB) **plus** the flight-data-recorder cap (64 GB / flight, AC-NEW-3). Reuse-across-flights tile cache stays resident; per-flight FDR rolls over after cap.
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## Sensors & Integration
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- High-rate **IMU** data is available from the flight controller via MAVLink.
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- The system communicates with the flight controller via MAVLink. Telemetry plumbing uses **MAVSDK**; the `GPS_INPUT` injection path is implemented via **pymavlink**, since MAVSDK does not expose a native `GPS_INPUT` API.
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- **Autopilot target: ArduPilot only** (with `GPS1_TYPE=14` for MAVLink GPS injection). PX4 is out of scope for the build; if it ever returns to scope it will use `VISION_POSITION_ESTIMATE`, not `GPS_INPUT`. (See `_docs/00_research/00_ac_assessment.md` Q-1.)
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- The system outputs WGS84 GPS coordinates to the flight controller as a replacement for the real GPS module (MAVLink GPS_INPUT, AC-4.3).
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- **Ground station: QGroundControl** is the supported GCS. Mission Planner is not in scope. Telemetry link is bandwidth-limited and is not the primary output channel; per-frame data stays on the local FDR (AC-NEW-3), GCS sees a 1–2 Hz downsampled summary (AC-6.1).
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## Failsafe & Safety
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- If the GPS-Denied system fails to produce any position estimate for **>3 s**, the autopilot falls back to IMU-only dead reckoning (AC-5.2). N=3 s rides through one sharp turn at cruise speed without tripping the failsafe.
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- The system must satisfy the false-position safety budget in AC-NEW-4 (P(error >500 m) <0.1%, P(error >1 km) <0.01% per flight).
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- Cold-start time-to-first-fix budget is **<30 s** from companion-computer boot (AC-NEW-1); spoofing-promotion latency is **<3 s** from FC's GPS-loss signal (AC-NEW-2).
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