Update dataset card (polygon-only schema)

README.md

@@ -1,26 +1,138 @@
 ---
-license: apache-2.0
-configs:
-- config_name: default
-  data_files:
-  - split: train
-    path: data/train-*
+license: "odbl"
+pretty_name: "OSM Polygon Wikidata Only"
+language: "en"
+task_categories:
+  - "other"
+tags:
+  - "openstreetmap"
+  - "geospatial"
+  - "wikidata"
+  - "polygons"
+  - "boundaries"
+  - "OSM"
+  - "PBF"
+  - "ODbL"
+size_categories:
+  - "n<1K"
 dataset_info:
   features:
-  - name: region
-    dtype: string
-  - name: osm_type
-    dtype: string
-  - name: osm_id
-    dtype: int64
-  - name: wikidata
-    dtype: string
-  - name: tags
-    dtype: string
+    - name: "region"
+      description: "Geofabrik region slug parsed from the source PBF filename (e.g. `monaco`)."
+    - name: "osm_type"
+      description: "OSM element type: `way` or `relation`."
+    - name: "osm_id"
+      description: "OpenStreetMap numeric identifier of the element."
+    - name: "wikidata"
+      description: "Wikidata Q-id, lifted into its own column for easy filtering and joins. Mirrors the OSM `wikidata` tag."
+    - name: "tags"
+      description: "Deterministic JSON object of all OSM tags except `wikidata`."
+    - name: "centroid"
+      description: "Polygon centroid as a GeoJSON Point string (RFC 7946: `[lon, lat]`)."
+    - name: "lat"
+      description: "Centroid latitude in decimal degrees (WGS84)."
+    - name: "lon"
+      description: "Centroid longitude in decimal degrees (WGS84)."
+    - name: "area_m2"
+      description: "Polygon area in square meters (WGS84-equirectangular approximation, accurate to <0.1% for polygons <100 km wide)."
+    - name: "area_km2"
+      description: "Polygon area in square kilometers (`area_m2 / 1_000_000`)."
+    - name: "name"
+      description: "Convenience column: `tags.name` if present, empty string otherwise."
+    - name: "source_pbf"
+      description: "Source PBF filename (e.g. `monaco-latest.osm.pbf`)."
+    - name: "extraction_version"
+      description: "Package version that produced the row."
+    - name: "extracted_at"
+      description: "ISO-8601 UTC timestamp at the moment the row was extracted."
   splits:
-  - name: train
-    num_bytes: 34540
-    num_examples: 58
-  download_size: 23776
-  dataset_size: 34540
+    - name: "train"
+      num_examples: 58
 ---
+
+# OSM Polygon Wikidata Only
+
+OpenStreetMap polygonal features (closed ways and multipolygon relations) carrying a non-empty `wikidata=*` tag, plus centroid and area metadata for each polygon.
+
+## Summary
+
+This dataset is built from Geofabrik `.osm.pbf` extracts. It contains every OSM polygon (closed way or multipolygon relation) that carries a non-empty `wikidata` tag. For each polygon the row records the centroid (as `lat`, `lon`, and a GeoJSON Point string), the polygon area in square meters and square kilometers, the full OSM tag set (minus `wikidata`), and provenance fields (`region`, `source_pbf`, `extraction_version`, `extracted_at`).
+
+## Data source
+
+- **Upstream**: [OpenStreetMap](https://www.openstreetmap.org/), distributed as country/region `.osm.pbf` extracts by [Geofabrik](https://download.geofabrik.de/).
+- **Filter**: keep only closed ways that carry a `wikidata=*` tag AND relations with `type=multipolygon` that carry a `wikidata=*` tag. All other elements (including nodes and tagged non-polygonal ways) are dropped.
+
+## Schema
+
+| Column | Type | Description |
+|---|---|---|
+| `region` | string | Geofabrik region slug parsed from the source PBF filename (e.g. `monaco`). |
+| `osm_type` | string | OSM element type: `way` or `relation`. |
+| `osm_id` | int64 | OpenStreetMap numeric identifier of the element. |
+| `wikidata` | string | Wikidata Q-id, lifted into its own column for easy filtering and joins. Mirrors the OSM `wikidata` tag. |
+| `tags` | string (JSON) | Deterministic JSON object of all OSM tags except `wikidata`. |
+| `centroid` | string (GeoJSON Point) | Polygon centroid as a GeoJSON Point string (RFC 7946: `[lon, lat]`). |
+| `lat` | float64 | Centroid latitude in decimal degrees (WGS84). |
+| `lon` | float64 | Centroid longitude in decimal degrees (WGS84). |
+| `area_m2` | float64 | Polygon area in square meters (WGS84-equirectangular approximation, accurate to <0.1% for polygons <100 km wide). |
+| `area_km2` | float64 | Polygon area in square kilometers (`area_m2 / 1_000_000`). |
+| `name` | string | Convenience column: `tags.name` if present, empty string otherwise. |
+| `source_pbf` | string | Source PBF filename (e.g. `monaco-latest.osm.pbf`). |
+| `extraction_version` | string | Package version that produced the row. |
+| `extracted_at` | string (ISO-8601 UTC) | ISO-8601 UTC timestamp at the moment the row was extracted. |
+
+## Loading
+
+```python
+from datasets import load_dataset
+
+ds = load_dataset("NoeFlandre/osm-polygon-wikidata-only", split="train")
+print(ds[0])
+```
+
+## Intended uses
+
+- Linking OSM polygons to Wikidata entries for cataloguing, research, or visualization.
+- Building gazetteers that combine OSM geometry with Wikidata labels.
+- Light ETL of polygon metadata (centroid + area) without re-parsing PBFs.
+
+## Limitations and biases
+
+- **Coverage** depends on which Geofabrik extracts were processed and at what snapshot date. Some regions may be stale; see `source_pbf` and `extracted_at` per row.
+- **Wikidata IDs are OSM tag values**, not independently validated. They may point to nonexistent, merged, or redirected Wikidata items.
+- **Geometry is reduced** to centroid + area. Full polygon coordinates are not stored to keep the dataset small.
+- **Equirectangular area approximation** is accurate to ~0.1% for polygons <100 km wide at non-polar latitudes. Very large polygons (countries) may have noticeable error.
+
+## Data freshness
+
+The dataset is regenerated from Geofabrik PBFs on demand. The current snapshot was generated at **2026-07-09 13:06:12 UTC** and contains **58** rows.
+
+## Licensing and attribution
+
+OpenStreetMap data is © OpenStreetMap contributors and licensed under the [Open Database License (ODbL) v1.0](https://opendatacommons.org/licenses/odbl/1-0/). **Any use of this dataset must preserve OSM attribution**: see [openstreetmap.org/copyright](https://www.openstreetmap.org/copyright) for the exact wording required when displaying or redistributing OSM-derived data.
+
+Wikidata IDs are obtained from the OSM `wikidata=*` tag values. Wikidata itself is © Wikimedia contributors under CC0; see [wikidata.org](https://www.wikidata.org/) for details.
+
+## Citation
+
+If you use this dataset in academic work, please cite OpenStreetMap and Geofabrik, for example:
+
+```bibtex
+@misc{openstreetmap,
+  title = {OpenStreetMap},
+  author = {{OpenStreetMap contributors}},
+  year = {2026},
+  howpublished = {\url{https://www.openstreetmap.org}},
+}
+```
+
+## Maintenance
+
+Re-run the pipeline against fresh Geofabrik PBFs and re-push the dataset. The CLI command is:
+
+```bash
+uv run osm-wikidata build --push
+```
+
+Issues and improvements are tracked on the associated GitHub repository.