gps-denied-onboard/_docs/00_research/00_ac_assessment.md

Acceptance Criteria Assessment

Accessed: 2026-05-01. Rerun after user-approved clarifications: 2026-05-01.

Research Scope

• Output class: Technical-component selection support.
• Novelty sensitivity: High for VPR, embedded AI, and autopilot integration; source preference is current papers and official docs.
• Boundary: Fixed-wing UAV, nadir navigation camera, ArduPilot Plane, Jetson Orin Nano Super, offline Azaion Suite Satellite Service cache, eastern/southern Ukraine terrain.

Acceptance Criteria

Criterion	Current Values	Researched Values / Evidence	Cost / Timeline Impact	Status
AC-1.1 / AC-1.2 frame-center accuracy	<=50 m for >=80%, <=20 m for >=50% in normal segments	Plausible only with periodic satellite anchoring plus VO/IMU propagation. Aerial VPR papers show the mechanism is viable but sensitive to weather, scale, repetition, and tile overlap.	High validation cost.	Keep, high-risk
AC-1.3 drift	VO-only <100 m, IMU-fused <50 m between anchors, anchor age reported	Updated AC now requires last_satellite_anchor_age_ms, binned validation, and degraded covariance after a solution-defined max anchor age.	Medium.	Updated
AC-1.4 confidence	95% covariance ellipse + source label	GPS_INPUT supports accuracy fields; source labels must be carried in telemetry/FDR because GPS_INPUT has no semantic label field.	Medium.	Keep
AC-2.1 registration	VO >95%; satellite anchoring measured separately	Split is correct: VO success is not the same as cross-domain satellite anchor success.	Medium-high.	Updated
AC-2.2 reprojection	<1 px VO, <2.5 px satellite anchor	Reasonable image-space gates, with coordinate error still dependent on calibration, orthorectification, and satellite georegistration.	Medium.	Keep
AC-3.x resilience	Outliers, sharp turns, disconnected segments, blackout	Technically feasible only through mode switching: VO failure triggers VPR/relocalization, blackout triggers IMU-only propagation with honest covariance growth.	High test cost.	Keep
AC-4.1 latency	<400 ms p95, <=10% frame drops, heavy VPR conditional	Aerial VPR survey reports some re-ranking paths too slow for steady-state use; solution must keep global VPR off the per-frame hot path.	High optimization cost.	Updated
AC-4.2 memory	<8 GB shared	Feasible if descriptors are compressed/pruned and indices are memory-mapped or loaded selectively.	Medium-high.	Keep
AC-4.3 MAVLink	v1 GPS_INPUT only via pymavlink	ArduPilot docs require GPS1_TYPE=14; MAVLink defines required lat/lon, velocity, fix, and accuracy fields. MAVSDK should remain telemetry-oriented.	Medium.	Keep
AC-5.2 failsafe	>3 s no estimate triggers fallback, Plane SITL verified	Copter docs are reference only. Plane-specific production parameters must be verified in SITL.	Medium.	Updated
AC-7 object localization	Level-flight AI-camera object GPS	Realistic under level-flight clause; maneuvering estimates must publish conservative bound.	Medium.	Keep
AC-8.x satellite cache	0.3-0.5 m/px, freshness, offline descriptors, VPR chunks	Resolution is feasible through commercial/service imagery. Storage must count descriptors unless separately budgeted.	Medium-high.	Updated
AC-NEW-1 / 2 startup and spoofing	<30 s first fix, <3 s promotion	Feasible only with prebuilt engines, warmed indices, and verified Plane GPS-health triggers.	Medium-high.	Keep with SITL gate
AC-NEW-3 FDR	<=64 GB per flight, no raw frames	Feasible with segment files and rollover.	Medium.	Keep
AC-NEW-4 / 7 safety budgets	False-position and cache-poisoning probabilities	Appropriate safety gates, but require Monte Carlo and representative flight/replay data.	High.	Keep
AC-NEW-5 environment	-20 C to +50 C, 25 W for 8 h	NVIDIA confirms 25 W mode; thermal design must prevent throttling.	Medium-high.	Keep

Restrictions Assessment

Restriction	Current Values	Researched Values / Evidence	Cost / Timeline Impact	Status
Camera source of truth	restrictions.md pins ADTi 20MP ~5472 x 3648	User confirmed restrictions.md is authoritative. Lens/FOV remains a design parameter.	Medium during module selection.	Updated
Fixed nadir camera	No gimbal stabilization	Good for orthorectification; turn/tilt requires attitude compensation and failure detection.	Medium.	Keep
Terrain/weather	Flat steppe/agricultural, seasonal classes included	Repetitive fields and seasonal changes are VPR hazards; validation must include those classes.	High validation cost.	Updated
Satellite Service boundary	Offline consumer of Suite Satellite Service	Strong separation; cache manifest and ingest-voting contract are required.	Medium.	Keep
10 GB cache	Includes imagery, manifests, overviews, descriptors unless split	Plausible at 0.5 m/px with compression; 0.3 m/px plus descriptors may exceed unless pruned.	Medium.	Updated
Jetson Orin Nano Super	67 TOPS INT8, 8 GB, 25 W	Official specs support the restriction; thermal throttling remains a risk.	Medium-high.	Keep
Test data gap	Sample imagery lacks IMU/ground truth	Public datasets help prototype, but final acceptance needs synchronized representative data.	High.	Updated

Key Findings

1. Use a hybrid estimator: VO/IMU for frame propagation, satellite/VPR anchors for absolute correction, ESKF covariance as the safety gate.
2. Do not run heavy VPR/re-ranking every frame; invoke it on cold start, VO failure, covariance growth, sharp turns, and disconnected segments.
3. Avoid GPL libraries in production dependencies unless the project accepts GPL obligations. GPL VIO/SLAM tools should be benchmarks or references, not selected production components.
4. The cache must be designed as imagery + metadata + descriptor index, not just raster tiles.
5. ArduPilot Plane SITL and representative camera+IMU data are blocking validation dependencies, but not blockers for solution drafting.

Sources

See _docs/00_research/01_source_registry.md for the detailed source list.