gps-denied-onboard/_docs/00_research/03_comparison_framework.md

Comparison Framework

Selected Framework Type

Mode B weak-point assessment with exact-fit validation.

Selected Dimensions

1. Functional fit against the Project Constraint Matrix.
2. Licensing and productization risk.
3. Jetson runtime and memory fit.
4. Cache/storage fit.
5. Validation evidence quality.
6. Security/safety impact.
7. Selection status.

Initial Population

Component Area	Candidate / Decision	Functional Fit	Runtime / Storage Fit	Evidence	Status
Runtime scheduling	Bounded latest-frame scheduler with explicit drop/backpressure policy	Fits AC-4.1 frame-drop allowance and AC-4.4 no-batching requirement	Prevents stale FIFO backlog when a frame takes near the 400 ms p95 budget	Fact #27	Selected
Relative motion	Custom planar VO/IMU	Fits fixed nadir monocular camera, flat terrain, FC attitude/altitude, and covariance output	Must run on downsampled/ROI imagery and skip under load	Facts #4, #9, #20	Selected
Relative motion	NVIDIA cuVSLAM	Official docs emphasize stereo-visual-inertial SLAM; not exact-fit for one fixed monocular nav camera	Good Jetson stack, but wrong input assumptions for v1	Facts #7, #20	Rejected for v1
Coarse VPR	AnyLoc/DINOv2-VLAD over chunks	Good retrieval shape for cross-domain top-K, conditional invocation only	49,152-d descriptors require PCA/quantization/index-size proof	Facts #5, #6, #19	Selected with compression gate
Local refinement	Official Magic Leap SuperPoint weights	Good technical candidate for local features	Product license blocks commercial use without separate grant	Fact #17	Rejected for product v1
Local refinement	ALIKED + LightGlue	Names a concrete license-cleared learned-feature candidate	Needs Jetson benchmark, ONNX/TensorRT proof, and cross-domain accuracy proof	Facts #18, #24	Selected candidate
Local refinement	OpenCV SIFT/AKAZE + classical matching	Commercial-safe baseline for geometric verification and regression tests	May be weaker on cross-domain sparse fields	Facts #10, #26	Selected baseline
Local refinement	DeDoDe	MIT-licensed learned-feature fallback with ONNX/TensorRT ports	Model size/runtime and DINOv2-related variants need validation	Fact #25	Experimental only
State estimation	ESKF in local NED/ENU	Owns covariance, source labels, outlier rejection, and false-position budget	CPU feasible if bounded; needs Monte Carlo calibration	Facts #1, #2, #9, #10	Selected
Flight-controller output	pymavlink GPS_INPUT only for v1	Matches ArduPilot replacement-GPS framing	Low runtime load; fields must be honest raw-GPS-sensor values	Facts #1, #2, #3	Selected
Flight-controller output	Dual GPS_INPUT + ODOMETRY	Richer covariance/yaw semantics, but overlaps source fusion	Version-specific EKF risk remains	Fact #3	Deferred to v1.1
Cache	0.3-0.5 m/px COG/GeoTIFF exchange + SQLite package	Correct service/onboard split	10 GB budget requires measured compression + descriptor/index proof	Facts #13, #16, #21	Selected with storage gate
Validation	Public datasets only	Useful for VPR/cross-view early proof	Does not cover project FC IMU timing and ArduPilot injection	Facts #22, #23	Insufficient alone
API	FastAPI local service	Fits OpenAPI/local control/object localization	Keep out of hot path; default docs at /docs, /redoc, OpenAPI path configurable	Fact #14, Context7 FastAPI docs	Selected

Rejected / Deferred Candidates

Candidate	Reason
Official SuperPoint pretrained weights as direct product dependency	Noncommercial research license blocks product use without separate commercial permission.
Uncompressed AnyLoc VLAD descriptors in the runtime cache	49,152-dimensional descriptors can consume hundreds of MB to GB once multi-scale chunks and variants are included.
Per-frame DINOv2 VPR	Wastes latency/thermal budget and conflicts with AC-8.6 conditional VPR.
GPS_INPUT + ODOMETRY dual emission in v1	Still too risky without version-pinned ArduPilot SITL proving no source double-fusion.
Public datasets as final validation substitute	They do not replace FC IMU, camera timing, thermal, and MAVLink injection evidence from the actual deployment stack.