Verify Ground Zero neighbor edges

AGRARIAN_DEVELOPMENT_ROADMAP.md

@@ -423,7 +423,7 @@ Target deliverable: A small group can join a server, spawn into one biome, gathe
 - [x] Add generated tile metadata record for the MVP tile.
 - [x] Verify terrain scale is 1 km x 1 km in Unreal.
 - [x] Verify terrain tile origin and centered Unreal bounds for the Ground Zero test map.
-- [ ] Verify neighboring tile edge coordinates against the registry before multi-tile stitching.
+- [x] Verify neighboring tile edge coordinates against the registry before multi-tile stitching.
 - [ ] Add foliage pass.
 - [~] Add resource nodes.
 - [ ] Add biome-appropriate natural resources based on Ground Zero.
@@ -1402,4 +1402,4 @@ Next version .01 priorities:
 
 Immediate next item:
 
-- [ ] Verify neighboring tile edge coordinates against the registry before multi-tile stitching.
+- [ ] Add foliage pass.

Data/Terrain/Analysis/gz_us_ca_pacifica_utm10n_e544_n4160/gz_us_ca_pacifica_utm10n_e544_n4160_neighbor_edge_verification.json

@@ -0,0 +1,289 @@
+{
+  "schema_version": 1,
+  "tile_id": "gz_us_ca_pacifica_utm10n_e544_n4160",
+  "registry_path": "Data/Tiles/ground_zero_tiles.json",
+  "grid_scheme": "prototype_utm_1km",
+  "verified_tile_count": 9,
+  "expected_neighbor_count": 8,
+  "found_neighbor_count": 8,
+  "all_passed": true,
+  "missing_neighbors": [],
+  "tile_shape_checks": [
+    {
+      "tile_id": "gz_us_ca_pacifica_utm10n_e544_n4160",
+      "passed": true,
+      "errors": []
+    },
+    {
+      "tile_id": "gz_us_ca_pacifica_utm10n_e543_n4159",
+      "passed": true,
+      "errors": []
+    },
+    {
+      "tile_id": "gz_us_ca_pacifica_utm10n_e544_n4159",
+      "passed": true,
+      "errors": []
+    },
+    {
+      "tile_id": "gz_us_ca_pacifica_utm10n_e545_n4159",
+      "passed": true,
+      "errors": []
+    },
+    {
+      "tile_id": "gz_us_ca_pacifica_utm10n_e543_n4160",
+      "passed": true,
+      "errors": []
+    },
+    {
+      "tile_id": "gz_us_ca_pacifica_utm10n_e545_n4160",
+      "passed": true,
+      "errors": []
+    },
+    {
+      "tile_id": "gz_us_ca_pacifica_utm10n_e543_n4161",
+      "passed": true,
+      "errors": []
+    },
+    {
+      "tile_id": "gz_us_ca_pacifica_utm10n_e544_n4161",
+      "passed": true,
+      "errors": []
+    },
+    {
+      "tile_id": "gz_us_ca_pacifica_utm10n_e545_n4161",
+      "passed": true,
+      "errors": []
+    }
+  ],
+  "neighbor_edge_checks": [
+    {
+      "direction": "n",
+      "neighbor_tile_id": "gz_us_ca_pacifica_utm10n_e544_n4161",
+      "expected_bounds_utm_m": {
+        "easting_min_m": 544000,
+        "northing_min_m": 4161000,
+        "easting_max_m": 545000,
+        "northing_max_m": 4162000
+      },
+      "actual_bounds_utm_m": {
+        "easting_min_m": 544000,
+        "northing_min_m": 4161000,
+        "easting_max_m": 545000,
+        "northing_max_m": 4162000
+      },
+      "shared_edge": {
+        "center_edge": "north",
+        "neighbor_edge": "south",
+        "shared_northing_m": 4161000,
+        "easting_span_m": [
+          544000,
+          545000
+        ]
+      },
+      "passed": true,
+      "errors": []
+    },
+    {
+      "direction": "ne",
+      "neighbor_tile_id": "gz_us_ca_pacifica_utm10n_e545_n4161",
+      "expected_bounds_utm_m": {
+        "easting_min_m": 545000,
+        "northing_min_m": 4161000,
+        "easting_max_m": 546000,
+        "northing_max_m": 4162000
+      },
+      "actual_bounds_utm_m": {
+        "easting_min_m": 545000,
+        "northing_min_m": 4161000,
+        "easting_max_m": 546000,
+        "northing_max_m": 4162000
+      },
+      "shared_edge": {
+        "center_corner_touch": "ne",
+        "corner_touch_only": true,
+        "expected_bounds": {
+          "easting_min_m": 545000,
+          "northing_min_m": 4161000,
+          "easting_max_m": 546000,
+          "northing_max_m": 4162000
+        }
+      },
+      "passed": true,
+      "errors": []
+    },
+    {
+      "direction": "e",
+      "neighbor_tile_id": "gz_us_ca_pacifica_utm10n_e545_n4160",
+      "expected_bounds_utm_m": {
+        "easting_min_m": 545000,
+        "northing_min_m": 4160000,
+        "easting_max_m": 546000,
+        "northing_max_m": 4161000
+      },
+      "actual_bounds_utm_m": {
+        "easting_min_m": 545000,
+        "northing_min_m": 4160000,
+        "easting_max_m": 546000,
+        "northing_max_m": 4161000
+      },
+      "shared_edge": {
+        "center_edge": "east",
+        "neighbor_edge": "west",
+        "shared_easting_m": 545000,
+        "northing_span_m": [
+          4160000,
+          4161000
+        ]
+      },
+      "passed": true,
+      "errors": []
+    },
+    {
+      "direction": "se",
+      "neighbor_tile_id": "gz_us_ca_pacifica_utm10n_e545_n4159",
+      "expected_bounds_utm_m": {
+        "easting_min_m": 545000,
+        "northing_min_m": 4159000,
+        "easting_max_m": 546000,
+        "northing_max_m": 4160000
+      },
+      "actual_bounds_utm_m": {
+        "easting_min_m": 545000,
+        "northing_min_m": 4159000,
+        "easting_max_m": 546000,
+        "northing_max_m": 4160000
+      },
+      "shared_edge": {
+        "center_corner_touch": "se",
+        "corner_touch_only": true,
+        "expected_bounds": {
+          "easting_min_m": 545000,
+          "northing_min_m": 4159000,
+          "easting_max_m": 546000,
+          "northing_max_m": 4160000
+        }
+      },
+      "passed": true,
+      "errors": []
+    },
+    {
+      "direction": "s",
+      "neighbor_tile_id": "gz_us_ca_pacifica_utm10n_e544_n4159",
+      "expected_bounds_utm_m": {
+        "easting_min_m": 544000,
+        "northing_min_m": 4159000,
+        "easting_max_m": 545000,
+        "northing_max_m": 4160000
+      },
+      "actual_bounds_utm_m": {
+        "easting_min_m": 544000,
+        "northing_min_m": 4159000,
+        "easting_max_m": 545000,
+        "northing_max_m": 4160000
+      },
+      "shared_edge": {
+        "center_edge": "south",
+        "neighbor_edge": "north",
+        "shared_northing_m": 4160000,
+        "easting_span_m": [
+          544000,
+          545000
+        ]
+      },
+      "passed": true,
+      "errors": []
+    },
+    {
+      "direction": "sw",
+      "neighbor_tile_id": "gz_us_ca_pacifica_utm10n_e543_n4159",
+      "expected_bounds_utm_m": {
+        "easting_min_m": 543000,
+        "northing_min_m": 4159000,
+        "easting_max_m": 544000,
+        "northing_max_m": 4160000
+      },
+      "actual_bounds_utm_m": {
+        "easting_min_m": 543000,
+        "northing_min_m": 4159000,
+        "easting_max_m": 544000,
+        "northing_max_m": 4160000
+      },
+      "shared_edge": {
+        "center_corner_touch": "sw",
+        "corner_touch_only": true,
+        "expected_bounds": {
+          "easting_min_m": 543000,
+          "northing_min_m": 4159000,
+          "easting_max_m": 544000,
+          "northing_max_m": 4160000
+        }
+      },
+      "passed": true,
+      "errors": []
+    },
+    {
+      "direction": "w",
+      "neighbor_tile_id": "gz_us_ca_pacifica_utm10n_e543_n4160",
+      "expected_bounds_utm_m": {
+        "easting_min_m": 543000,
+        "northing_min_m": 4160000,
+        "easting_max_m": 544000,
+        "northing_max_m": 4161000
+      },
+      "actual_bounds_utm_m": {
+        "easting_min_m": 543000,
+        "northing_min_m": 4160000,
+        "easting_max_m": 544000,
+        "northing_max_m": 4161000
+      },
+      "shared_edge": {
+        "center_edge": "west",
+        "neighbor_edge": "east",
+        "shared_easting_m": 544000,
+        "northing_span_m": [
+          4160000,
+          4161000
+        ]
+      },
+      "passed": true,
+      "errors": []
+    },
+    {
+      "direction": "nw",
+      "neighbor_tile_id": "gz_us_ca_pacifica_utm10n_e543_n4161",
+      "expected_bounds_utm_m": {
+        "easting_min_m": 543000,
+        "northing_min_m": 4161000,
+        "easting_max_m": 544000,
+        "northing_max_m": 4162000
+      },
+      "actual_bounds_utm_m": {
+        "easting_min_m": 543000,
+        "northing_min_m": 4161000,
+        "easting_max_m": 544000,
+        "northing_max_m": 4162000
+      },
+      "shared_edge": {
+        "center_corner_touch": "nw",
+        "corner_touch_only": true,
+        "expected_bounds": {
+          "easting_min_m": 543000,
+          "northing_min_m": 4161000,
+          "easting_max_m": 544000,
+          "northing_max_m": 4162000
+        }
+      },
+      "passed": true,
+      "errors": []
+    }
+  ],
+  "stitching_decision": {
+    "ready_for_coordinate_based_neighbor_stitching": true,
+    "notes": [
+      "All Ground Zero neighbor placeholders align on exact 1000m UTM boundaries.",
+      "Cardinal neighbors share full 1km edges with no gap or overlap.",
+      "Diagonal neighbors touch at corners only.",
+      "This verifies registry coordinates, not yet elevation seam continuity."
+    ]
+  }
+}

Docs/Terrain/GroundZeroNeighborEdges.md

@@ -0,0 +1,38 @@
+# 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.

Scripts/verify_ground_zero_neighbor_edges.py

@@ -0,0 +1,223 @@
+#!/usr/bin/env python3
+"""Verify Ground Zero neighbor tile edges before multi-tile stitching."""
+
+from __future__ import annotations
+
+import json
+from pathlib import Path
+
+
+REPO_ROOT = Path(__file__).resolve().parents[1]
+REGISTRY_PATH = REPO_ROOT / "Data/Tiles/ground_zero_tiles.json"
+OUTPUT_PATH = (
+    REPO_ROOT
+    / "Data/Terrain/Analysis/gz_us_ca_pacifica_utm10n_e544_n4160/"
+    / "gz_us_ca_pacifica_utm10n_e544_n4160_neighbor_edge_verification.json"
+)
+
+GROUND_ZERO_TILE_ID = "gz_us_ca_pacifica_utm10n_e544_n4160"
+TILE_SIZE_M = 1000
+
+DIRECTION_OFFSETS = {
+    "n": (0, 1),
+    "ne": (1, 1),
+    "e": (1, 0),
+    "se": (1, -1),
+    "s": (0, -1),
+    "sw": (-1, -1),
+    "w": (-1, 0),
+    "nw": (-1, 1),
+}
+
+
+def load_registry() -> dict:
+    return json.loads(REGISTRY_PATH.read_text())
+
+
+def grid(tile: dict) -> dict:
+    return tile["grid"]
+
+
+def expected_tile_id(tile_family: str, easting_min_m: int, northing_min_m: int) -> str:
+    return f"{tile_family}_e{easting_min_m // 1000}_n{northing_min_m // 1000}"
+
+
+def verify_tile_shape(tile: dict) -> list[str]:
+    errors: list[str] = []
+    g = grid(tile)
+    width = g["easting_max_m"] - g["easting_min_m"]
+    height = g["northing_max_m"] - g["northing_min_m"]
+
+    if width != TILE_SIZE_M:
+        errors.append(f"width is {width}m, expected {TILE_SIZE_M}m")
+    if height != TILE_SIZE_M:
+        errors.append(f"height is {height}m, expected {TILE_SIZE_M}m")
+    if g["tile_size_m"] != TILE_SIZE_M:
+        errors.append(f"tile_size_m is {g['tile_size_m']}, expected {TILE_SIZE_M}")
+    if g["utm_zone"] != "10N":
+        errors.append(f"utm_zone is {g['utm_zone']}, expected 10N")
+    if g["projection"] != "WGS84 / UTM zone 10N":
+        errors.append(f"projection is {g['projection']}, expected WGS84 / UTM zone 10N")
+
+    tile_family = "_".join(tile["tile_id"].split("_")[:-2])
+    expected_id = expected_tile_id(tile_family, g["easting_min_m"], g["northing_min_m"])
+    if tile["tile_id"] != expected_id:
+        errors.append(f"tile_id is {tile['tile_id']}, expected {expected_id}")
+
+    return errors
+
+
+def expected_bounds(center_grid: dict, dx: int, dy: int) -> dict:
+    easting_min = center_grid["easting_min_m"] + dx * TILE_SIZE_M
+    northing_min = center_grid["northing_min_m"] + dy * TILE_SIZE_M
+    return {
+        "easting_min_m": easting_min,
+        "northing_min_m": northing_min,
+        "easting_max_m": easting_min + TILE_SIZE_M,
+        "northing_max_m": northing_min + TILE_SIZE_M,
+    }
+
+
+def verify_neighbor_edge(direction: str, center: dict, neighbor: dict) -> dict:
+    center_grid = grid(center)
+    neighbor_grid = grid(neighbor)
+    dx, dy = DIRECTION_OFFSETS[direction]
+    expected = expected_bounds(center_grid, dx, dy)
+
+    errors: list[str] = []
+    for key, expected_value in expected.items():
+        actual_value = neighbor_grid[key]
+        if actual_value != expected_value:
+            errors.append(f"{key} is {actual_value}, expected {expected_value}")
+
+    if direction == "n":
+        shared_edge = {
+            "center_edge": "north",
+            "neighbor_edge": "south",
+            "shared_northing_m": center_grid["northing_max_m"],
+            "easting_span_m": [center_grid["easting_min_m"], center_grid["easting_max_m"]],
+        }
+        if neighbor_grid["northing_min_m"] != center_grid["northing_max_m"]:
+            errors.append("north neighbor south edge does not meet Ground Zero north edge")
+    elif direction == "s":
+        shared_edge = {
+            "center_edge": "south",
+            "neighbor_edge": "north",
+            "shared_northing_m": center_grid["northing_min_m"],
+            "easting_span_m": [center_grid["easting_min_m"], center_grid["easting_max_m"]],
+        }
+        if neighbor_grid["northing_max_m"] != center_grid["northing_min_m"]:
+            errors.append("south neighbor north edge does not meet Ground Zero south edge")
+    elif direction == "e":
+        shared_edge = {
+            "center_edge": "east",
+            "neighbor_edge": "west",
+            "shared_easting_m": center_grid["easting_max_m"],
+            "northing_span_m": [center_grid["northing_min_m"], center_grid["northing_max_m"]],
+        }
+        if neighbor_grid["easting_min_m"] != center_grid["easting_max_m"]:
+            errors.append("east neighbor west edge does not meet Ground Zero east edge")
+    elif direction == "w":
+        shared_edge = {
+            "center_edge": "west",
+            "neighbor_edge": "east",
+            "shared_easting_m": center_grid["easting_min_m"],
+            "northing_span_m": [center_grid["northing_min_m"], center_grid["northing_max_m"]],
+        }
+        if neighbor_grid["easting_max_m"] != center_grid["easting_min_m"]:
+            errors.append("west neighbor east edge does not meet Ground Zero west edge")
+    else:
+        shared_edge = {
+            "center_corner_touch": direction,
+            "corner_touch_only": True,
+            "expected_bounds": expected,
+        }
+
+    return {
+        "direction": direction,
+        "neighbor_tile_id": neighbor["tile_id"],
+        "expected_bounds_utm_m": expected,
+        "actual_bounds_utm_m": {
+            "easting_min_m": neighbor_grid["easting_min_m"],
+            "northing_min_m": neighbor_grid["northing_min_m"],
+            "easting_max_m": neighbor_grid["easting_max_m"],
+            "northing_max_m": neighbor_grid["northing_max_m"],
+        },
+        "shared_edge": shared_edge,
+        "passed": not errors,
+        "errors": errors,
+    }
+
+
+def main() -> None:
+    registry = load_registry()
+    tiles_by_id = {tile["tile_id"]: tile for tile in registry["tiles"]}
+    center = tiles_by_id[GROUND_ZERO_TILE_ID]
+
+    tile_shape_checks = []
+    for tile in registry["tiles"]:
+        errors = verify_tile_shape(tile)
+        tile_shape_checks.append(
+            {
+                "tile_id": tile["tile_id"],
+                "passed": not errors,
+                "errors": errors,
+            }
+        )
+
+    neighbor_checks = []
+    missing_neighbors = []
+    for direction in ["n", "ne", "e", "se", "s", "sw", "w", "nw"]:
+        neighbor_id = center["neighbors"].get(direction)
+        if not neighbor_id or neighbor_id not in tiles_by_id:
+            missing_neighbors.append({"direction": direction, "neighbor_tile_id": neighbor_id})
+            continue
+        neighbor_checks.append(verify_neighbor_edge(direction, center, tiles_by_id[neighbor_id]))
+
+    passed = (
+        not missing_neighbors
+        and all(check["passed"] for check in neighbor_checks)
+        and all(check["passed"] for check in tile_shape_checks)
+    )
+
+    result = {
+        "schema_version": 1,
+        "tile_id": GROUND_ZERO_TILE_ID,
+        "registry_path": str(REGISTRY_PATH.relative_to(REPO_ROOT)),
+        "grid_scheme": registry["grid_scheme"],
+        "verified_tile_count": len(registry["tiles"]),
+        "expected_neighbor_count": 8,
+        "found_neighbor_count": len(neighbor_checks),
+        "all_passed": passed,
+        "missing_neighbors": missing_neighbors,
+        "tile_shape_checks": tile_shape_checks,
+        "neighbor_edge_checks": neighbor_checks,
+        "stitching_decision": {
+            "ready_for_coordinate_based_neighbor_stitching": passed,
+            "notes": [
+                "All Ground Zero neighbor placeholders align on exact 1000m UTM boundaries.",
+                "Cardinal neighbors share full 1km edges with no gap or overlap.",
+                "Diagonal neighbors touch at corners only.",
+                "This verifies registry coordinates, not yet elevation seam continuity.",
+            ],
+        },
+    }
+
+    OUTPUT_PATH.parent.mkdir(parents=True, exist_ok=True)
+    OUTPUT_PATH.write_text(json.dumps(result, indent=2) + "\n")
+    print(f"Wrote {OUTPUT_PATH.relative_to(REPO_ROOT)}")
+    print(
+        json.dumps(
+            {
+                "all_passed": result["all_passed"],
+                "verified_tile_count": result["verified_tile_count"],
+                "found_neighbor_count": result["found_neighbor_count"],
+                "missing_neighbors": result["missing_neighbors"],
+            },
+            indent=2,
+        )
+    )
+
+
+if __name__ == "__main__":
+    main()