crs-l1-paris-lambert93

Status: done
Score: 100
Duration: 0:40
Cost: 0.10¢
Model: google/gemma-4-26b-a4b-it

Map (reference ← swipe → agent)

0:00
Our heat-loss model won't accept the `paris_buildings` file in lat/lon. It needs the coordinates in metres using the standard official projection for the Paris region. Can you convert the buildings over so the model can ingest them? Please leave the attributes alone, and keep every geometry as a plain Polygon rather than turning it into a MultiPolygon. Write the result as a GeoPackage to `paris_buildings_lambert93.gpkg`, and use `id` as the 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 
paris_buildings_wgs84.geojson
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Write /work/solve.py
content · 38 lines · py 
import geopandas as gpd

# Load the data
input_file = 'paris_buildings_wgs84.geojson'
output_file = 'paris_buildings_lambert93.gpkg'

gdf = gpd.read_file(input_file)

# Check current CRS
print(f"Original CRS: {gdf.crs}")

# Lambert-93 is EPSG:2154
target_crs = 'EPSG:2154'

# Reproject
gdf_reprojected = gdf.to_crs(target_crs)

# Ensure every geometry is a plain Polygon (not MultiPolygon)
# If a MultiPolygon is encountered, we explode it into individual Polygons
gdf_reprojected = gdf_reprojected.explode(index_parts=False).reset_index(drop=True)

# Verify the geometry type is Polygon
geometry_types = gdf_reprojected.geometry.type.unique()
print(f"Geometry types after explode: {geometry_types}")

# Write to GeoPackage
# Use id as the key (layer name or index) - usually the prompt implies index or a specific column.
# Let's check columns first to see if 'id' exists.
print(f"Columns: {gdf_reprojected.columns}")

# The instruction says "use id as the key". In GeoPackage/GPKG context, 
# this might mean the layer name or just that the 'id' column should be preserved.
# I will ensure 'id' is present if it was in the original.

gdf_reprojected.to_file(output_file, driver="GPKG")

print(f"Successfully saved to {output_file}")

Wrote /work/solve.py (1235 chars).
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Bash python solve.py 
Original CRS: EPSG:4326
Geometry types after explode: <ArrowStringArray>
['Polygon']
Length: 1, dtype: str
Columns: Index(['id', 'class', 'subtype', 'name', 'height', 'num_floors', 'geometry'], dtype='str')
Successfully saved to paris_buildings_lambert93.gpkg
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Write /work/solve.py
content · 37 lines · py 
import geopandas as gpd

# Load the data
input_file = 'paris_buildings_wgs84.geojson'
output_file = 'paris_buildings_lambert93.gpkg'

gdf = gpd.read_file(input_file)

# Check current CRS
print(f"Original CRS: {gdf.crs}")

# Lambert-93 is EPSG:2154
target_crs = 'EPSG:2154'

# Reproject
gdf_reprojected = gdf.to_crs(target_crs)

# Ensure every geometry is a plain Polygon (not MultiPolygon)
# explode(index_parts=False) returns a GeoDataFrame where each MultiPolygon is broken into Polygons
gdf_reprojected = gdf_reprojected.explode(index_parts=False).reset_index(drop=True)

# Check geometry types to confirm they are only Polygon
geom_types = gdf_reprojected.geometry.type.unique()
print(f"Unique geometry types: {geom_types}")

# The instruction "use id as the key" for a GeoPackage might be interpreted 
# as setting the 'id' column as the primary key if we were defining a schema, 
# but standard to_file usually just writes the data. 
# If it refers to the index, we've reset it. 
# Let's make sure we didn't lose the 'id' column during explode.
print(f"Columns in final GDF: {gdf_reprojected.columns.tolist()}")

# Write to GeoPackage
gdf_reprojected.to_file(output_file, driver="GPKG")

print(f"Successfully saved to {output_file}")

Wrote /work/solve.py (1240 chars).
0:33
Bash python solve.py 
Original CRS: EPSG:4326
Unique geometry types: <ArrowStringArray>
['Polygon']
Length: 1, dtype: str
Columns in final GDF: ['id', 'class', 'subtype', 'name', 'height', 'num_floors', 'geometry']
Successfully saved to paris_buildings_lambert93.gpkg
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