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What Land Does This Satellite Pixel Show?

From the four spectral bands of a small patch of Landsat image, is it red soil, cotton crop, grey soil, damp soil, vegetation stubble or very damp soil? It's the classic test for turning satellite pixels into a land map.

Use caseClimatePredictionModel evaluation

The table

Three-by-three pixel neighbourhoods from a Landsat image, with 36 multispectral values and the land-cover class of the centre pixel. It's in Welt's research catalogue as Satellite Image Attributes, 6,435 rows by 37 columns, licensed CC BY 4.0. The catalogue measures its signal at 0.86. At 6,435 rows and 36 features the table is larger than the model limits allow, so the walkthrough evaluates and fits on a seeded sample of 4,000 rows. TabICLv2 and Kumo Tabular Medium compete.

Walkthrough

  1. Load it from the catalogue

    Find the table, read its recorded target and print the column names.

    import pandas as pd
    from welt import Client
    
    with Client() as client:
        item = client.research_datasets(q="satellite image attributes", limit=1)["items"][0]
        info = client.research_dataset(item["id"])
        data = client.load_research_dataset(item["id"])
    
    target = info["targets"][0]
    target = target["name"] if isinstance(target, dict) else target
    print([column["name"] for column in info["schema"]], target)
  2. Pick the rows

    Set aside 20 rows to predict at the end. The models learn from a seeded sample of 4,000 of the rest, the most this table's width allows.

    known = data.dropna(subset=[target])
    new_rows = known.sample(20, random_state=1)
    table = known.drop(new_rows.index).sample(4000, random_state=7)
  3. Compare the models and predict

    The models compete on the same folds against a simple guess, then the top-ranked one is fitted on the whole table. ROC AUC runs from 0.5, a coin toss, to 1, a perfect ranking, and a lower Brier score means the probabilities can be trusted more. The last table puts each prediction next to the real answer.

    with Client() as client:
        evaluation = client.evaluate(table, target, task="classification", seed=7,
                                     models=["tabicl-v2", "kumo-medium"])
        model = evaluation.fit()
    
    print(evaluation.summary()[["name", "rank", "roc_auc_mean", "brier_mean"]])
    features = new_rows.drop(columns=target)
    print(pd.DataFrame({"actual": new_rows[target].values, "predicted": model.predict(features),
                        "probability": model.predict_proba(features).max(axis=1)}))

What you get

A class per pixelWith a probability for each type of land.
A strong signalThe catalogue measures a high signal.
A classic benchmarkCompare with decades of published results.

Try it

Use Open with to run the research datasets notebook in Colab, Kaggle or Jupyter and search for "satellite image attributes", or run the code above after pip install "welt-client[parquet]".