geo-l1-capetown-building-centroids
Map (reference ← swipe → agent)
0:00
The addressing tool only renders points, so I need a centroid layer off `capetown_buildings` — one centroid per footprint. Keep the building IDs so we can join back to the polygon master later: ensure the output carries a `building_id` column with the building identifier from the input. Every row must have a non-empty `building_id`.
Write the result to `building_centroids.geojson` as a GeoJSON FeatureCollection with Point geometry only and the `building_id` column described above.
0:00
System info
{
"adapter": "openrouter",
"model": "deepseek/deepseek-v4-flash",
"base_url": "https://openrouter.ai/api/v1"
}
0:14
Let me start by reading the input file to understand its structure.
0:14
Bash
ls /work/
capetown_buildings.cpg capetown_buildings.dbf capetown_buildings.prj capetown_buildings.shp capetown_buildings.shx
0:19
Let's inspect the input shapefile to understand its attributes, especially the building ID column.
0:19
Bash
cd /work && python -c "
cd /work && python -c "
import geopandas as gpd
gdf = gpd.read_file('capetown_buildings.shp')
print('Columns:', gdf.columns.tolist())
print('CRS:', gdf.crs)
print('Shape:', gdf.shape)
print('--- First 3 rows ---')
print(gdf.head(3).to_string())
print('--- dtypes ---')
print(gdf.dtypes)
"
Columns: ['building_i', 'geometry'] CRS: EPSG:32734 Shape: (122, 2) --- First 3 rows --- building_i geometry 0 BLD00001 POLYGON ((261901.274 6243490.255, 261869.707 6243515.945, 261858.441 6243525.384, 261865.989 6243534.664, 261877.279 6243525.036, 261930.771 6243480.329, 261958.032 6243513.755, 261964.366 6243521.262, 261918.064 6243558.946, 261939.138 6243584.891, 261937.202 6243586.474, 261926.074 6243595.563, 261930.563 6243601.025, 261934.846 6243606.249, 261937.252 6243609.184, 261935.817 6243610.324, 261926.486 6243617.837, 261974.611 6243676.759, 261976.321 6243675.359, 261981.266 6243681.499, 261989.68 6243675.084, 261996.043 6243670.05, 262009.009 6243659.964, 262015.954 6243668.229, 262041.203 6243648.008, 262055.508 6243636.547, 262058.851 6243633.867, 262072.658 6243622.371, 262073.555 6243623.503, 262079.973 6243618.104, 262085.991 6243613.138, 262082.95 6243609.344, 262094.327 6243599.884, 262102.822 6243609.798, 262107.272 6243615.381, 262150.387 6243580.424, 262162.325 6243570.734, 262154.272 6243560.91, 262149.217 6243554.734, 262153.311 6243556.424, 262161.47 6243549.836, 262164.672 6243547.253, 262166.853 6243545.487, 262206.802 6243513.558, 262226.443 6243497.391, 262260.669 6243470.058, 262283.419 6243451.283, 262297.657 6243439.542, 262423.496 6243336.668, 262462.938 6243304.193, 262463.171 6243282.667, 262459.192 6243203.266, 262457.3 6243204.927, 262410.862 6243237.105, 262409.554 6243235.03, 262396.426 6243248.286, 262385.455 6243257.079, 262365.66 6243273.465, 262244.772 6243371.179, 262224.288 6243346.037, 262231.636 6243340.439, 262172.879 6243269.021, 262164.682 6243259.414, 262168.908 6243256.546, 262166.172 6243251.638, 262157.398 6243254.726, 262156.971 6243252.917, 262106.663 6243272.61, 262108.786 6243275.371, 262085.724 6243283.716, 262069.144 6243296.963, 262038.642 6243322.657, 262036.344 6243319.858, 262029.572 6243325.36, 262030.721 6243326.754, 262031.924 6243328.227, 262017.93 6243339.84, 261942.911 6243400.655, 261932.038 6243409.561, 261925.532 6243414.792, 261903.264 6243433.101, 261874.393 6243457.171, 261901.274 6243490.255)) 1 BLD00002 POLYGON ((261917.732 6243289.478, 261986.733 6243231.709, 261983.749 6243228.216, 261914.747 6243285.996, 261917.732 6243289.478)) 2 BLD00003 POLYGON ((261757.159 6243198.786, 261777.731 6243180.934, 261782.32 6243177.242, 261784.078 6243175.788, 261770.349 6243159.139, 261746.887 6243178.228, 261745.542 6243179.847, 261744.927 6243181.841, 261745.245 6243184.291, 261746.348 6243186.072, 261757.159 6243198.786)) --- dtypes --- building_i str geometry geometry dtype: object
0:32
The input has a column named `building_i` (not `building_id`). The task says to keep the building IDs and ensure the output carries a `building_id` column. So I need to rename `building_i` to `building_id` in the output. Let me write the script.
0:32
Write
/work/solve.py
content · 24 lines · py
import geopandas as gpd
INPUT = "/work/capetown_buildings.shp"
OUTPUT = "/work/building_centroids.geojson"
# Read the building footprints
gdf = gpd.read_file(INPUT)
# Rename building_i -> building_id
gdf = gdf.rename(columns={"building_i": "building_id"})
# Compute centroid for each footprint, keeping building_id
# Use representative point (centroid) — centroid is geometrically correct
centroids = gdf.copy()
centroids["geometry"] = centroids.geometry.centroid
# Verify no null building_id
null_bid = centroids["building_id"].isna()
if null_bid.any():
raise ValueError(f"Found {null_bid.sum()} rows with null building_id — cannot proceed.")
# Write to GeoJSON FeatureCollection
centroids.to_file(OUTPUT, driver="GeoJSON")
print(f"Written {len(centroids)} centroids to {OUTPUT}")Wrote /work/solve.py (791 chars).
0:48
Let me run the script and then verify the output.
0:48
Bash
cd /work && python solve.py
Written 122 centroids to /work/building_centroids.geojson
0:59
Let me verify the output file exists and sanity-check it.
0:59
Bash
cd /work && python -c "
cd /work && python -c "
import geopandas as gpd
gdf = gpd.read_file('building_centroids.geojson')
print('Shape:', gdf.shape)
print('Columns:', gdf.columns.tolist())
print('CRS:', gdf.crs)
print('--- First 5 rows ---')
print(gdf.head(5).to_string())
print('--- Geometry types ---')
print(gdf.geometry.geom_type.value_counts())
print('--- Null building_id? ---')
print(gdf['building_id'].isna().sum())
print('--- Empty building_id? ---')
print((gdf['building_id'] == '').sum())
"
Shape: (122, 2) Columns: ['building_id', 'geometry'] CRS: EPSG:32734 --- First 5 rows --- building_id geometry 0 BLD00001 POINT (262131.639 6243436.712) 1 BLD00002 POINT (261950.751 6243258.841) 2 BLD00003 POINT (261763.586 6243178.854) 3 BLD00004 POINT (261684.818 6243473.068) 4 BLD00005 POINT (261890.235 6243301.424) --- Geometry types --- Point 122 Name: count, dtype: int64 --- Null building_id? --- 0 --- Empty building_id? --- 0
1:04
Everything checks out: - 122 centroids (one per footprint) - Column is `building_id` (renamed from `building_i`) - All geometry is Point - No null or empty building_id values - Written as GeoJSON FeatureCollection - CRS is preserved (EPSG:32734) Let me also verify the file exists and is valid GeoJSON.
1:04
Bash
ls -lh /work/building_centroids.geojson
-rw-r--r-- 1 agent agent 21K Jun 16 18:55 /work/building_centroids.geojson
1:12
Everything checks out: - Output file `building_centroids.geojson` exists - Contains 122 Point features (one per footprint) - Has `building_id` column (renamed from `building_i` of the input) - No null or empty `building_id` values - CRS is EPSG:32734 (preserved from input, metric coordinates ~10⁵ range — correct for UTM zone 34S) The task is complete.
1:12