crs-l1-nyc-webmercator-cycleways
Map (reference ← swipe → agent)
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The nyc_cycleways file is what our tile-renderer spat out. Our web map client can't handle the coordinates as-is — it needs standard geographic coordinates that any browser mapping library can consume natively. Convert the geometries so they're in plain latitude/longitude, leave the attributes alone. GeoParquet to nyc_cycleways_wgs84.geoparquet.
Keep every geometry as a plain LineString — do not upcast to MultiLineString. Each feature must preserve all original columns, with id as the feature identity 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
nyc_cycleways_webmercator.geoparquet
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Write
solve.py
content · 45 lines · py
# /// script
# requires-python = ">=3.12"
# dependencies = ["geopandas", "pyarrow", "shapely"]
# ///
import geopandas as gpd
def convert_to_wgs84(input_path, output_path):
# Read the input GeoParquet file
gdf = gpd.read_parquet(input_path)
# Reproject to WGS84 (EPSG:4326)
gdf = gdf.to_crs(epsg=4326)
# Ensure all geometries are LineString (not MultiLineString)
# We can use explode to turn MultiLineString into multiple LineStrings
# But the instruction says "Keep every geometry as a plain LineString — do not upcast to MultiLineString."
# Usually, "upcast" refers to converting LineString to MultiLineString.
# If we have MultiLineStrings, we should break them down into individual LineStrings.
# Explode MultiLineStrings into LineStrings
gdf = gdf.explode(index_parts=False)
# In case there are any other non-LineString geometries (though unlikely for cycleways),
# we should ensure they are LineStrings if possible, but typically explode handles MultiLineString -> LineString.
# However, the instruction is specifically about not upcasting.
# It implies if a geometry is a MultiLineString, it should be multiple features or individual LineStrings.
# Using explode(index_parts=False) will create multiple rows for a single MultiLineString feature,
# which is the standard way to handle this while maintaining attributes.
# The instruction says "Each feature must preserve all original columns, with id as the feature identity key."
# If we explode, we might duplicate the 'id'. If 'id' is meant to be the unique identifier for the *row* in the output,
# we might need to reconsider. But usually, in GIS, 'id' refers to the original feature ID.
# Let's check the content first to see what we are dealing with.
# Save to GeoParquet
gdf.to_parquet(output_path)
print(f"Converted {input_path} to {output_path}")
if __name__ == "__main__":
input_file = "nyc_cycleways_webmercator.geoparquet"
output_file = "nyc_cycleways_wgs84.geoparquet"
convert_to_wgs84(input_file, output_file)
Wrote /home/nhp/project/benchmark/harness/.sessions/4a7f11898d394fbfbf1ba141c5468cbf/solve.py (2129 chars).
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Bash
uv run solve.py
Converted nyc_cycleways_webmercator.geoparquet to nyc_cycleways_wgs84.geoparquet
Downloading pyarrow (46.6MiB) Downloaded pyarrow Installed 11 packages in 254ms
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Write
verify.py
content · 36 lines · py
# /// script
# requires-python = ">=3.12"
# dependencies = ["geopandas", "pyarrow", "shapely"]
# ///
import geopandas as gpd
def verify_output(input_path, output_path):
gdf_in = gpd.read_parquet(input_path)
gdf_out = gpd.read_parquet(output_path)
print(f"Input CRS: {gdf_in.crs}")
print(f"Output CRS: {gdf_out.crs}")
print(f"Input geometry types: {gdf_in.geometry.type.unique()}")
print(f"Output geometry types: {gdf_out.geometry.type.unique()}")
# Check if any MultiLineString exists in the output
multi_linestring_count = (gdf_out.geometry.type == 'MultiLineString').sum()
print(f"Number of MultiLineStrings in output: {multi_linestring_count}")
# Check columns
print(f"Input columns: {gdf_in.columns.tolist()}")
print(f"Output columns: {gdf_out.columns.tolist()}")
# Check if id is present
if 'id' in gdf_out.columns:
print("Column 'id' is present.")
else:
print("Column 'id' is MISSING!")
if __name__ == "__main__":
input_file = "nyc_cycleways_webmercator.geoparquet"
output_file = "nyc_cycleways_wgs84.geoparquet"
verify_output(input_file, output_file)
Wrote /home/nhp/project/benchmark/harness/.sessions/4a7f11898d394fbfbf1ba141c5468cbf/verify.py (1174 chars).
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Bash
uv run verify.py
Input CRS: {"$schema": "https://proj.org/schemas/v0.7/projjson.schema.json", "type": "ProjectedCRS", "name": "WGS 84 / Pseudo-Mercator", "base_crs": {"name": "WGS 84", "datum_ensemble": {"name": "World Geodetic System 1984 ensemble", "members": [{"name": "World Geodetic System 1984 (Transit)"}, {"name": "World Geodetic System 1984 (G730)"}, {"name": "World Geodetic System 1984 (G873)"}, {"name": "World Geodetic System 1984 (G1150)"}, {"name": "World Geodetic System 1984 (G1674)"}, {"name": "World Geodetic System 1984 (G1762)"}, {"name": "World Geodetic System 1984 (G2139)"}, {"name": "World Geodetic System 1984 (G2296)"}], "ellipsoid": {"name": "WGS 84", "semi_major_axis": 6378137, "inverse_flattening": 298.257223563}, "accuracy": "2.0", "id": {"authority": "EPSG", "code": 6326}}, "coordinate_system": {"subtype": "ellipsoidal", "axis": [{"name": "Geodetic latitude", "abbreviation": "Lat", "direction": "north", "unit": "degree"}, {"name": "Geodetic longitude", "abbreviation": "Lon", "direction": "east", "unit": "degree"}]}, "id": {"authority": "EPSG", "code": 4326}}, "conversion": {"name": "Popular Visualisation Pseudo-Mercator", "method": {"name": "Popular Visualisation Pseudo Mercator", "id": {"authority": "EPSG", "code": 1024}}, "parameters": [{"name": "Latitude of natural origin", "value": 0, "unit": "degree", "id": {"authority": "EPSG", "code": 8801}}, {"name": "Longitude of natural origin", "value": 0, "unit": "degree", "id": {"authority": "EPSG", "code": 8802}}, {"name": "False easting", "value": 0, "unit": "metre", "id": {"authority": "EPSG", "code": 8806}}, {"name": "False northing", "value": 0, "unit": "metre", "id": {"authority": "EPSG", "code": 8807}}]}, "coordinate_system": {"subtype": "Cartesian", "axis": [{"name": "Easting", "abbreviation": "X", "direction": "east", "unit": "metre"}, {"name": "Northing", "abbreviation": "Y", "direction": "north", "unit": "metre"}]}, "scope": "Web mapping and visualisation.", "area": "World between 85.06\u00b0S and 85.06\u00b0N.", "bbox": {"south_latitude": -85.06, "west_longitude": -180, "north_latitude": 85.06, "east_longitude": 180}, "id": {"authority": "EPSG", "code": 3857}}
Output CRS: {"$schema": "https://proj.org/schemas/v0.7/projjson.schema.json", "type": "GeographicCRS", "name": "WGS 84", "datum_ensemble": {"name": "World Geodetic System 1984 ensemble", "members": [{"name": "World Geodetic System 1984 (Transit)"}, {"name": "World Geodetic System 1984 (G730)"}, {"name": "World Geodetic System 1984 (G873)"}, {"name": "World Geodetic System 1984 (G1150)"}, {"name": "World Geodetic System 1984 (G1674)"}, {"name": "World Geodetic System 1984 (G1762)"}, {"name": "World Geodetic System 1984 (G2139)"}, {"name": "World Geodetic System 1984 (G2296)"}], "ellipsoid": {"name": "WGS 84", "semi_major_axis": 6378137, "inverse_flattening": 298.257223563}, "accuracy": "2.0", "id": {"authority": "EPSG", "code": 6326}}, "coordinate_system": {"subtype": "ellipsoidal", "axis": [{"name": "Geodetic latitude", "abbreviation": "Lat", "direction": "north", "unit": "degree"}, {"name": "Geodetic longitude", "abbreviation": "Lon", "direction": "east", "unit": "degree"}]}, "scope": "Horizontal component of 3D system.", "area": "World.", "bbox": {"south_latitude": -90, "west_longitude": -180, "north_latitude": 90, "east_longitude": 180}, "id": {"authority": "EPSG", "code": 4326}}
Input geometry types: <ArrowStringArray>
['LineString']
Length: 1, dtype: str
Output geometry types: <ArrowStringArray>
['LineString']
Length: 1, dtype: str
Number of MultiLineStrings in output: 0
Input columns: ['id', 'class', 'subclass', 'name', 'geometry']
Output columns: ['id', 'class', 'subclass', 'name', 'geometry']
Column 'id' is present.
Installed 11 packages in 130ms
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