dc-l1-tokyo-ring-orientation

Status: done
Score: 100
Duration: 0:56
Cost: 0.31¢
Model: google/gemma-4-26b-a4b-it

Map (reference ← swipe → agent)

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tokyo_buildings_legacy.geojson is a footprint export from an old in-house tool. When we load it into web-based GeoJSON viewers, building interiors are shaded incorrectly: holes appear filled and exteriors render as empty space. Our tile-server import script also rejects every feature with geometry warnings. Fix the geometries so that standard GeoJSON web viewers render them correctly. Attributes must be untouched. Output to tokyo_buildings_fixed.geojson. Every feature must remain a Polygon with interior rings and holes preserved exactly as they are; do not flatten them. feature_id is the join key.
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System info 
{
  "adapter": "openrouter",
  "model": "google/gemma-4-26b-a4b-it",
  "base_url": "https://openrouter.ai/api/v1"
}
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Bash ls -F 
ls -F

tokyo_buildings_legacy.geojson
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Write /work/inspect_data.py
content · 14 lines · py 
import geopandas as gpd

# Load the data to see what we are dealing with
try:
    gdf = gpd.read_file('tokyo_buildings_legacy.geojson')
    print("Columns:", gdf.columns.tolist())
    print("First few rows:")
    print(gdf.head())
    print("\nGeometry types:")
    print(gdf.geom_type.value_counts())
    print("\nTotal features:", len(gdf))
except Exception as e:
    print(f"Error loading file: {e}")

Wrote /work/inspect_data.py (404 chars).
0:07
Bash python /work/inspect_data.py 
python /work/inspect_data.py

Columns: ['feature_id', 'overture_id', 'name_primary', 'building_class', 'height', 'geometry']
First few rows:
   feature_id  ...                                           geometry
0           1  ...  POLYGON ((139.70291 35.65924, 139.7028 35.6592...
1           2  ...  POLYGON ((139.70109 35.6602, 139.70109 35.6600...
2           3  ...  POLYGON ((139.70112 35.66167, 139.70099 35.661...
3           4  ...  POLYGON ((139.70327 35.66018, 139.7033 35.6601...
4           5  ...  POLYGON ((139.70158 35.6592, 139.70161 35.6592...

[5 rows x 6 columns]

Geometry types:
Polygon    100
Name: count, dtype: int64

Total features: 100
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Write /work/fix_geometries.py
content · 84 lines · py 
import geopandas as gpd
from shapely.geometry import Polygon, MultiPolygon

def check_ring_orientation(polygon):
    """
    In GeoJSON (RFC 7946), exterior rings should be counter-clockwise
    and interior rings should be clockwise. 
    Note: Some tools/older standards had this reversed.
    The user says 'interiors are shaded incorrectly: holes appear filled and 
    exteriors render as empty space'. 
    This strongly suggests the orientation is reversed (exterior is CW, interior is CCW).
    """
    if not isinstance(polygon, Polygon):
        return []
    
    # Check exterior
    # A polygon is CCW if its signed area is positive.
    # Shapely uses a right-handed system where CCW is positive area?
    # Let's use the .is_ccw property or check signed area.
    
    # Actually, let's use the 'orient' function from shapely which is designed for this.
    return []

def fix_geometries(gdf):
    # We use shapely.geometry.polygon.orient(polygon, sign=1.0)
    # sign=1.0 means exterior is CCW, interior is CW.
    # sign=-1.0 means exterior is CW, interior is CCW.
    # Standard GeoJSON (RFC 7946) says exterior should be CCW.
    
    from shapely.geometry import Polygon, MultiPolygon
    from shapely.ops import orient

    def fix_single_geom(geom):
        if geom.is_empty:
            return geom
        if isinstance(geom, Polygon):
            # orient(polygon, sign=1.0) makes exterior CCW and interior CW.
            return orient(geom, sign=1.0)
        elif isinstance(geom, MultiPolygon):
            return MultiPolygon([orient(p, sign=1.0) for p in geom.geoms])
        else:
            return geom

    gdf['geometry'] = gdf['geometry'].apply(fix_single_geom)
    return gdf

# Try to reproduce the "incorrect" state by checking orientations of current rings
def analyze_orientations(gdf):
    print("\nAnalyzing ring orientations (assuming current state is wrong):")
    for idx, row in gdf.iterrows():
        geom = row['geometry']
        if isinstance(geom, Polygon):
            # Exterior
            ext = list(geom.exterior.coords)
            # Compute signed area of exterior
            area_ext = 0
            for i in range(len(ext)-1):
                area_ext += (ext[i][0] * ext[i+1][1] - ext[i+1][0] * ext[i][1])
            print(f"ID {row['feature_id']} - Ext Area Sign: {1 if area_ext > 0 else -1}")
            
            # Interiors
            for i, ring in enumerate(geom.interiors):
                coords = list(ring.coords)
                area_int = 0
                for j in range(len(coords)-1):
                    area_int += (coords[j][0] * coords[j+1][1] - coords[j+1][0] * coords[j][1])
                print(f"  ID {row['feature_id']} - Int Ring {i} Area Sign: {1 if area_int > 0 else -1}")

# Load
gdf = gpd.read_file('tokyo_buildings_legacy.geojson')
analyze_orientations(gdf)

# Fix
print("\nApplying fix (orienting to RFC 7946)...")
gdf_fixed = fix_geometries(gdf)

# Save
gdf_fixed.to_file('tokyo_buildings_fixed.geojson', driver='GeoJSON')
print("Saved to tokyo_buildings_fixed.geojson")

# Verify the fix
print("\nVerifying fixed orientations:")
analyze_orientations(gdf_fixed)

Wrote /work/fix_geometries.py (3165 chars).
0:30
Bash python /work/fix_geometries.py 
python /work/fix_geometries.py

Analyzing ring orientations (assuming current state is wrong):
ID 1 - Ext Area Sign: -1
ID 2 - Ext Area Sign: -1
ID 3 - Ext Area Sign: -1
ID 4 - Ext Area Sign: -1
ID 5 - Ext Area Sign: -1
ID 6 - Ext Area Sign: -1
  ID 6 - Int Ring 0 Area Sign: 1
ID 7 - Ext Area Sign: -1
ID 8 - Ext Area Sign: -1
ID 9 - Ext Area Sign: -1
ID 10 - Ext Area Sign: -1
ID 11 - Ext Area Sign: -1
ID 12 - Ext Area Sign: -1
ID 13 - Ext Area Sign: -1
ID 14 - Ext Area Sign: -1
ID 15 - Ext Area Sign: -1
ID 16 - Ext Area Sign: -1
ID 17 - Ext Area Sign: -1
ID 18 - Ext Area Sign: -1
  ID 18 - Int Ring 0 Area Sign: 1
ID 19 - Ext Area Sign: -1
ID 20 - Ext Area Sign: -1
ID 21 - Ext Area Sign: -1
ID 22 - Ext Area Sign: -1
ID 23 - Ext Area Sign: -1
ID 24 - Ext Area Sign: -1
ID 25 - Ext Area Sign: -1
ID 26 - Ext Area Sign: -1
ID 27 - Ext Area Sign: -1
ID 28 - Ext Area Sign: -1
ID 29 - Ext Area Sign: -1
ID 30 - Ext Area Sign: -1
ID 31 - Ext Area Sign: -1
ID 32 - Ext Area Sign: -1
  ID 32 - Int Ring 0 Area Sign: 1
ID 33 - Ext Area Sign: -1
ID 34 - Ext Area Sign: -1
ID 35 - Ext Area Sign: -1
ID 36 - Ext Area Sign: -1
ID 37 - Ext Area Sign: -1
ID 38 - Ext Area Sign: -1
ID 39 - Ext Area Sign: -1
ID 40 - Ext Area Sign: -1
ID 41 - Ext Area Sign: -1
ID 42 - Ext Area Sign: -1
ID 43 - Ext Area Sign: -1
ID 44 - Ext Area Sign: -1
ID 45 - Ext Area Sign: -1
ID 46 - Ext Area Sign: -1
ID 47 - Ext Area Sign: -1
ID 48 - Ext Area Sign: -1
ID 49 - Ext Area Sign: -1
ID 50 - Ext Area Sign: -1
  ID 50 - Int Ring 0 Area Sign: 1
ID 51 - Ext Area Sign: -1
ID 52 - Ext Area Sign: -1
ID 53 - Ext Area Sign: -1
ID 54 - Ext Area Sign: -1
ID 55 - Ext Area Sign: -1
ID 56 - Ext Area Sign: -1
ID 57 - Ext Area Sign: -1
ID 58 - Ext Area Sign: -1
ID 59 - Ext Area Sign: -1
ID 60 - Ext Area Sign: -1
ID 61 - Ext Area Sign: -1
ID 62 - Ext Area Sign: -1
ID 63 - Ext Area Sign: -1
ID 64 - Ext Area Sign: -1
ID 65 - Ext Area Sign: -1
ID 66 - Ext Area Sign: -1
ID 67 - Ext Area Sign: -1
ID 68 - Ext Area Sign: -1
ID 69 - Ext Area Sign: -1
ID 70 - Ext Area Sign: -1
ID 71 - Ext Area Sign: -1
ID 72 - Ext Area Sign: -1
ID 73 - Ext Area Sign: -1
ID 74 - Ext Area Sign: -1
  ID 74 - Int Ring 0 Area Sign: 1
ID 75 - Ext Area Sign: -1
ID 76 - Ext Area Sign: -1
ID 77 - Ext Area Sign: -1
ID 78 - Ext Area Sign: -1
ID 79 - Ext Area Sign: -1
ID 80 - Ext Area Sign: -1
ID 81 - Ext Area Sign: -1
ID 82 - Ext Area Sign: -1
ID 83 - Ext Area Sign: -1
ID 84 - Ext Area Sign: -1
ID 85 - Ext Area Sign: -1
ID 86 - Ext Area Sign: -1
ID 87 - Ext Area Sign: -1
ID 88 - Ext Area Sign: -1
ID 89 - Ext Area Sign: -1
ID 90 - Ext Area Sign: -1
ID 91 - Ext Area Sign: -1
ID 92 - Ext Area Sign: -1
ID 93 - Ext Area Sign: -1
ID 94 - Ext Area Sign: -1
ID 95 - Ext Area Sign: -1
ID 96 - Ext Area Sign: -1
ID 97 - Ext Area Sign: -1
ID 98 - Ext Area Sign: -1
ID 99 - Ext Area Sign: -1
ID 100 - Ext Area Sign: -1

Applying fix (orienting to RFC 7946)...
Saved to tokyo_buildings_fixed.geojson

Verifying fixed orientations:

Analyzing ring orientations (assuming current state is wrong):
ID 1 - Ext Area Sign: 1
ID 2 - Ext Area Sign: 1
ID 3 - Ext Area Sign: 1
ID 4 - Ext Area Sign: 1
ID 5 - Ext Area Sign: 1
ID 6 - Ext Area Sign: 1
  ID 6 - Int Ring 0 Area Sign: -1
ID 7 - Ext Area Sign: 1
ID 8 - Ext Area Sign: 1
ID 9 - Ext Area Sign: 1
ID 10 - Ext Area Sign: 1
ID 11 - Ext Area Sign: 1
ID 12 - Ext Area Sign: 1
ID 13 - Ext Area Sign: 1
ID 14 - Ext Area Sign: 1
ID 15 - Ext Area Sign: 1
ID 16 - Ext Area Sign: 1
ID 17 - Ext Area Sign: 1
ID 18 - Ext Area Sign: 1
  ID 18 - Int Ring 0 Area Sign: -1
ID 19 - Ext Area Sign: 1
ID 20 - Ext Area Sign: 1
ID 21 - Ext Area Sign: 1
ID 22 - Ext Area Sign: 1
ID 23 - Ext Area Sign: 1
ID 24 - Ext Area Sign: 1
ID 25 - Ext Area Sign: 1
ID 26 - Ext Area Sign: 1
ID 27 - Ext Area Sign: 1
ID 28 - Ext Area Sign: 1
ID 29 - Ext Area Sign: 1
ID 30 - Ext Area Sign: 1
ID 31 - Ext Area Sign: 1
ID 32 - Ext Area Sign: 1
  ID 32 - Int Ring 0 Area Sign: -1
ID 33 - Ext Area Sign: 1
ID 34 - Ext Area Sign: 1
ID 35 - Ext Area Sign: 1
ID 36 - Ext Area Sign: 1
ID 37 - Ext Area Sign: 1
ID 38 - Ext Area Sign: 1
ID 39 - Ext Area Sign: 1
ID 40 - Ext Area Sign: 1
ID 41 - Ext Area Sign: 1
ID 42 - Ext Area Sign: 1
ID 43 - Ext Area Sign: 1
ID 44 - Ext Area Sign: 1
ID 45 - Ext Area Sign: 1
ID 46 - Ext Area Sign: 1
ID 47 - Ext Area Sign: 1
ID 48 - Ext Area Sign: 1
ID 49 - Ext Area Sign: 1
ID 50 - Ext Area Sign: 1
  ID 50 - Int Ring 0 Area Sign: -1
ID 51 - Ext Area Sign: 1
ID 52 - Ext Area Sign: 1
ID 53 - Ext Area Sign: 1
ID 54 - Ext Area Sign: 1
ID 55 - Ext Area Sign: 1
ID 56 - Ext Area Sign: 1
ID 57 - Ext Area Sign: 1
ID 58 - Ext Area Sign: 1
ID 59 - Ext Area Sign: 1
ID 60 - Ext Area Sign: 1
ID 61 - Ext Area Sign: 1
ID 62 - Ext Area Sign: 1
ID 63 - Ext Area Sign: 1
ID 64 - Ext Area Sign: 1
ID 65 - Ext Area Sign: 1
ID 66 - Ext Area Sign: 1
ID 67 - Ext Area Sign: 1
ID 68 - Ext Area Sign: 1
ID 69 - Ext Area Sign: 1
ID 70 - Ext Area Sign: 1
ID 71 - Ext Area Sign: 1
ID 72 - Ext Area Sign: 1
ID 73 - Ext Area Sign: 1
ID 74 - Ext Area Sign: 1
  ID 74 - Int Ring 0 Area Sign: -1
ID 75 - Ext Area Sign: 1
ID 76 - Ext Area Sign: 1
ID 77 - Ext Area Sign: 1
ID 78 - Ext Area Sign: 1
ID 79 - Ext Area Sign: 1
ID 80 - Ext Area Sign: 1
ID 81 - Ext Area Sign: 1
ID 82 - Ext Area Sign: 1
ID 83 - Ext Area Sign: 1
ID 84 - Ext Area Sign: 1
ID 85 - Ext Area Sign: 1
ID 86 - Ext Area Sign: 1
ID 87 - Ext Area Sign: 1
ID 88 - Ext Area Sign: 1
ID 89 - Ext Area Sign: 1
ID 90 - Ext Area Sign: 1
ID 91 - Ext Area Sign: 1
ID 92 - Ext Area Sign: 1
ID 93 - Ext Area Sign: 1
ID 94 - Ext Area Sign: 1
ID 95 - Ext Area Sign: 1
ID 96 - Ext Area Sign: 1
ID 97 - Ext Area Sign: 1
ID 98 - Ext Area Sign: 1
ID 99 - Ext Area Sign: 1
ID 100 - Ext Area Sign: 1
0:34
Bash # I'll also do a quick check to see if there are any invalid geometries like sel... 
# I'll also do a quick check to see if there are any invalid geometries like self-intersections
# that might be causing the tile-server to reject them.
python -c "import geopandas as gpd; gdf = gpd.read_file('tokyo_buildings_legacy.geojson'); print(gdf.is_valid.value_counts())"

True    100
Name: count, dtype: int64
0:42
Write /work/final_fix.py
content · 30 lines · py 
import geopandas as gpd
from shapely.geometry import Polygon, MultiPolygon
from shapely.ops import orient

def fix_geometries(gdf):
    def fix_single_geom(geom):
        if geom.is_empty:
            return geom
        if isinstance(geom, Polygon):
            # RFC 7946: Exterior is CCW (sign=1.0), Interior is CW
            return orient(geom, sign=1.0)
        elif isinstance(geom, MultiPolygon):
            return MultiPolygon([orient(p, sign=1.0) for p in geom.geoms])
        else:
            return geom

    gdf['geometry'] = gdf['geometry'].apply(fix_single_geom)
    return gdf

if __name__ == "__main__":
    # Load the data
    gdf = gpd.read_file('tokyo_buildings_legacy.geojson')
    
    # Apply the fix
    gdf_fixed = fix_geometries(gdf)
    
    # Save the result
    gdf_fixed.to_file('tokyo_buildings_fixed.geojson', driver='GeoJSON')
    print("Successfully fixed geometries and saved to tokyo_buildings_fixed.geojson")

Wrote /work/final_fix.py (948 chars).
0:43
Bash python /work/final_fix.py 
python /work/final_fix.py

Successfully fixed geometries and saved to tokyo_buildings_fixed.geojson
0:46
Bash # Check if any geometries became invalid after the fix (should not happen with o... 
# Check if any geometries became invalid after the fix (should not happen with orient)
python -c "import geopandas as gpd; gdf = gpd.read_file('tokyo_buildings_fixed.geojson'); print(gdf.is_valid.value_counts())"

True    100
Name: count, dtype: int64
0:55