Preface

With traffic and weather datasets ready, the next step is to link each freeway gantry to its closest weather station using geographic coordinates.

Gantry Locations

Download gantry latitude and longitude from the open data portal.

Matching Algorithm

Combine gantry and station coordinates, then compute distances using a simplified Pythagorean formula—sufficient for short ranges within Taiwan.

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import pandas as pd
import numpy as np

stations = pd.read_csv('stations.csv')
gantries = pd.read_csv('gantries.csv')

s = stations[['lat','lon']].to_numpy()
g = gantries[['lat','lon']].to_numpy()

# compute all pairwise distances
dists = np.sqrt(((g[:,None,:]-s[None,:,:])**2).sum(axis=2))
indices = dists.argmin(axis=1)

gantries['station_id'] = stations.iloc[indices]['id'].values

The resulting mapping lets us attach weather features from the nearest station to each gantry for model training.

Summary

This preprocessing step ensures that traffic records can be enriched with corresponding meteorological data.