# Ground Zero Neighbor Edge Verification

The Ground Zero tile and its eight immediate neighbor placeholders were checked
against the tile registry before any multi-tile stitching work.

## Inputs

- Registry: `Data/Tiles/ground_zero_tiles.json`
- Verification script: `Scripts/verify_ground_zero_neighbor_edges.py`
- Output:
  `Data/Terrain/Analysis/gz_us_ca_pacifica_utm10n_e544_n4160/gz_us_ca_pacifica_utm10n_e544_n4160_neighbor_edge_verification.json`

## Result

The registry coordinate pass succeeded.

- Ground Zero tile:
  `gz_us_ca_pacifica_utm10n_e544_n4160`
- Ground Zero bounds:
  `544000,4160000 -> 545000,4161000` in EPSG:26910 / UTM zone 10N.
- Verified tile count: `9`
- Found neighbor count: `8`
- All tiles use `1000 m x 1000 m` bounds.
- All tile IDs match their minimum UTM kilometer coordinates.
- North, south, east, and west neighbors share exact full 1 km edges with the
  Ground Zero tile.
- Northeast, southeast, southwest, and northwest neighbors touch Ground Zero at
  corners only.

## Stitching Decision

The registry is ready for coordinate-based neighbor stitching around Ground
Zero. This pass verifies tile bounds and adjacency only; it does not verify
elevation seam continuity because neighbor DEM extraction has not been run yet.

The next terrain stitching pass should extract or generate the relevant
neighbor DEMs, compare edge sample elevations, and then choose the seam blending
rule.
