# L3 Metric Refinement Component

## Detailed Description
**L3 Metric Refinement** provides the "Pinpoint" accuracy. It takes a pair of images: the current UAV frame and a candidate Satellite Tile (provided by L2 or determined by the State Estimator's prediction).

It uses **LiteSAM** to find dense correspondences between the aerial and satellite views. It computes a Homography and solves for the absolute world coordinate of the UAV center, achieving pixel-level accuracy.

## API Methods

### `refine_pose`
- **Input:** `uav_frame: FrameObject`, `satellite_tile: SatelliteTile`, `prior_yaw: float` (optional)
- **Output:** `L3Result`
- **Description:**
    1. Preprocesses images for LiteSAM.
    2. Infers dense matches.
    3. Filters outliers (RANSAC).
    4. Computes Homography $H$.
    5. Decomposes $H$ into rotation and translation (using camera intrinsics and tile GSD).
    6. Returns `{ abs_lat: float, abs_lon: float, yaw: float, confidence: float, match_inliers: int }`.
- **Test Cases:**
    - Perfect match pair -> Accurate Lat/Lon.
    - Mismatched pair (wrong tile) -> Low inlier count, Low confidence.

## Integration Tests
- **Accuracy Verification:** Use a ground-truth pair (UAV image + known correct Satellite tile). Verify calculated Lat/Lon error is < 20 meters.

## Non-functional Tests
- **Robustness:** Test with satellite images from different seasons (if available) or synthetically altered (color shift) to verify LiteSAM's semantic robustness.