# municipality-boundary-geoshape-2020

Graph-local municipality boundary shape shards for the municipality proportional swing page.

## Purpose

- provide prefecture-scoped GeoJSON polygons for public graph rendering
- provide region-scoped municipality polygons for public graph rendering
- join boundary features to graph payload rows by `jis_code`
- keep geometry as a view-layer shape, not as canonical election facts

## Source

- upstream: Geoshape historical administrative area dataset beta
- mirror used by builder: `conv4ja/geoshapes-jp-static`
- original polygon source: MLIT National Land Numerical Information administrative area data

## Row Grain

- one GeoJSON feature = one source boundary feature mapped to one graph selector `jis_code`
- designated-city parent selectors are represented by child ward polygons with the same parent `jis_code`

## Selector

- primary selector: `prefecture_code`
- region selector: `region_id`
- join key for graph payload: `properties.jis_code`

## Boundary

This dataset is a graph/view-layer shape. It does not alter canonical facts, vote totals, party definitions, or municipality transition facts.

Source rings whose coordinates fall outside the Japan display bounds are dropped during graph-local shape generation. This prevents upstream placeholder coordinates such as `[0, 0]` from breaking Leaflet viewport bounds.

## Known Gaps

- Geoshape static source is based on 2020 administrative polygons. Current Hamamatsu ward codes `22138`, `22139`, and `22140` do not exist in that source and are recorded in `latest/catalog.json:missing_source_codes`.