# Glossary

## Domain Terms

| Term | Definition | Source |
|------|-----------|--------|
| Tile | A single satellite imagery square (typically 256×256 px) at a specific zoom level and coordinate | modules/services_tile_service.md |
| Region | A square geographic area defined by center point and size in meters; the unit of work for batch tile downloads | modules/services_region_service.md |
| Route | An ordered sequence of geographic waypoints with interpolated intermediate points | modules/services_route_service.md |
| Route Point | A single lat/lon coordinate on a route; either "original" (user-provided waypoint) or "intermediate" (system-generated) | modules/dataaccess_models.md |
| Geofence | A rectangular geographic boundary (NW + SE corners) used to filter which route points receive map tile coverage | components/05_route_management/description.md |
| Zoom Level | Google Maps tile resolution level (1–20); higher = more detail, smaller ground coverage per tile | modules/common_configs.md |
| Stitch | Compositing multiple tiles into a single larger image with optional markers/borders | modules/services_region_service.md |
| Layer 1 | Satellite imagery from external providers (provider-agnostic; first implementation: Google Maps) | user clarification |
| Layer 2 | UAV-captured nadir camera imagery (orthogonal tiles uploaded post-flight) | user clarification |
| Nadir Camera | Downward-facing camera on a UAV capturing ground imagery during flight | user clarification |
| GPS-Denied Service | The consuming system: a UAV navigation service operating without GPS, using satellite/UAV imagery for positioning | user clarification |
| Slippy Map Coordinates | Tile X/Y indices in the Web Mercator projection grid (standard for web map tile servers) | data_model.md |
| Version | Integer year (e.g., 2025) used to invalidate tile cache when Google Maps imagery is updated | data_model.md |

## Technical Terms

| Term | Definition | Source |
|------|-----------|--------|
| Region Request Queue | In-process bounded `Channel<Guid>` that decouples HTTP request submission from background processing | modules/services_region_request_queue.md |
| Session Token | Provider-specific authentication token (e.g., Google Maps) embedded in tile download URLs; each provider may use different auth mechanisms | modules/services_google_maps_downloader.md |
| ISatelliteDownloader | Interface abstracting satellite imagery providers; first implementation: Google Maps (GoogleMapsDownloaderV2) | modules/common_interfaces.md |
| DbUp | .NET library for forward-only SQL schema migrations via numbered embedded scripts | modules/dataaccess_database_migrator.md |
| Tile Deduplication | Mechanism using DB unique index + ConcurrentDictionary to prevent re-downloading identical tiles | modules/services_google_maps_downloader.md |

## Abbreviations

| Abbrev | Meaning |
|--------|---------|
| MGRS | Military Grid Reference System (endpoint planned, currently stub) |
| UAV | Unmanned Aerial Vehicle |
| NFR | Non-Functional Requirement |
| DI | Dependency Injection |
| DTO | Data Transfer Object |
| CSV | Comma-Separated Values (tile manifest output format) |