gps-denied-onboard/_docs/02_document/glossary.md

Glossary

Status: confirmed-by-user
Date: 2026-05-01

Aerial VPR

Visual place recognition over aerial/nadir imagery; used to retrieve candidate satellite/cache chunks for a UAV frame. (source: solution.md)

ADTi 20MP 20L V1

Selected navigation-camera family. Public product pages list Sony APS-C CMOS, 5456 x 3632 max image size, 23.20 x 15.40 mm sensor, 4.25 um pixel pitch, Sony E mount, and 2 fps continuous capture; final manufacturer specification remains a verification risk. (source: restrictions.md, user-confirmed open-question review)

Anchor

Accepted absolute visual match to a georeferenced cache tile, used to correct VO/IMU drift. (source: acceptance_criteria.md, solution.md)

ArduPilot Plane SITL

Simulation environment used to verify GPS_INPUT, spoofing, failsafe, and MAVLink behavior with the production Plane parameter set. (source: acceptance_criteria.md, tests/environment.md)

BASALT VIO

Selected production relative visual-inertial odometry candidate. It consumes calibrated navigation-camera frames and IMU data but does not own the product's safety, anchor, cache, or MAVLink semantics. (source: solution.md)

Cache Poisoning

Failure mode where a misaligned onboard-generated tile is written back and later corrupts future satellite-cache anchors. (source: acceptance_criteria.md)

COG Tile

Cloud Optimized GeoTIFF raster object used as the write-new unit for georeferenced service tiles and generated onboard tiles. (source: solution.md)

FDR

Flight Data Recorder. Bounded per-flight recorder for estimates, IMU traces, emitted MAVLink, health telemetry, tile writes, and audit evidence; raw nav/AI frames are not retained. (source: acceptance_criteria.md, solution.md)

Generated Tile

In-flight orthorectified tile created from navigation-camera imagery and stored locally for post-flight Satellite Service sync. (source: acceptance_criteria.md)

GPS_INPUT

MAVLink message used as the ArduPilot GPS substitute in v1. It carries WGS84 coordinates, fix type, accuracy fields, and ignore flags. (source: acceptance_criteria.md, solution.md)

Kimera Backup

BSD-friendly VIO backup candidate if BASALT fails project replay/runtime gates. (source: solution.md)

Mahalanobis Gate

Statistical consistency gate used to reject anchor updates that are inconsistent with the current estimator state and covariance. (source: solution.md)

Nadir Camera

Fixed downward-pointing navigation camera used for localization. It is not gimbal-stabilized. (source: restrictions.md)

OpenVINS Reference

GPLv3 VIO/covariance baseline used for replay comparison and uncertainty calibration; not the default production dependency. (source: solution.md)

Public Replay Dataset

External dataset used to cover validation gaps in the current sample data, especially synchronized nadir camera, IMU, GNSS/ground truth, and reference imagery. MUN-FRL and ALTO are first-choice candidates. (source: tests/test-data.md)

QGroundControl

Supported ground station that receives downsampled status and failsafe messages at 1-2 Hz. (source: restrictions.md, acceptance_criteria.md)

Representative Replay Rig

Final acceptance dataset or hardware setup from the target flight profile with synchronized nav camera, FC IMU/attitude/airspeed/altitude, emitted MAVLink, and ground truth. (source: acceptance_criteria.md, tests/test-data.md)

Safety/Anchor Wrapper

Project-owned layer around BASALT that calibrates confidence, fuses satellite anchors, owns source labels, handles degraded modes, gates generated tiles, and emits MAVLink outputs. (source: solution.md)

Satellite Service

External Azaion Suite component that prepares the offline satellite cache before flight and ingests generated tiles after landing. The onboard system does not call it in-flight. (source: restrictions.md)

Source Label

Categorical label attached to every estimate: {satellite_anchored, vo_extrapolated, dead_reckoned}. (source: acceptance_criteria.md)

Tile Freshness

Runtime age gate for cache tiles: active-conflict sectors require newer imagery than stable rear sectors. (source: acceptance_criteria.md)

Visual Blackout

State where the navigation camera provides no usable localization signal because of clouds, occlusion, whiteout, or similar visual loss. (source: acceptance_criteria.md)

VPR Chunk

Ground-footprint-sized retrieval unit, approximately 600-800 m with overlap, decoupled from the storage tile convention. (source: acceptance_criteria.md)