国土地理院の住所検索APIと逆ジオコーダーの使い方：表記ゆれと複数候補を実測

[
  {
    "geometry": { "coordinates": [139.744385, 35.677414], "type": "Point" },
    "type": "Feature",
    "properties": { "addressCode": "", "title": "東京都千代田区永田町一丁目７番" }
  }
]

{"results":{"muniCd":"13101","lv01Nm":"永田町一丁目"}}

GSI.MUNI_ARRAY["13101"] = '13,東京都,13101,千代田区';
GSI.MUNI_ARRAY["8220"] = '8,茨城県,8220,つくば市';
GSI.MUNI_ARRAY["11107"] = '11,埼玉県,11107,さいたま市　浦和区';

// gsi-check.mjs — 依存なし。住所検索の候補を判定し、逆ジオコーダーの市区町村コードで照合する
// 使い方（オンライン）:  node gsi-check.mjs "東京都千代田区永田町1-7-1"
// 使い方（保存済み応答で判定だけ）: node gsi-check.mjs --offline
import { readFile } from 'node:fs/promises';

const UA = 'gsi-check-example/0.1 (+https://codeagent.jp/)';
const SEARCH = 'https://msearch.gsi.go.jp/address-search/AddressSearch?q=';
const REVERSE = 'https://mreversegeocoder.gsi.go.jp/reverse-geocoder/LonLatToAddress';
const MUNI = 'https://maps.gsi.go.jp/js/muni.js';

const toHalf = (s) => s.replace(/[０-９]/g, (c) => String.fromCharCode(c.charCodeAt(0) - 0xfee0));

// muni.js の行 GSI.MUNI_ARRAY["13101"] = '13,東京都,13101,千代田区'; を Map にする
function parseMuni(js) {
  const map = new Map();
  for (const m of js.matchAll(/MUNI_ARRAY\["(\d+)"\]\s*=\s*'([^']+)'/g)) {
    const [, pref, , city] = m[2].split(',');
    map.set(m[1], { pref, city: city.replace(/[\s　]/g, '') });
  }
  return map;
}

// 返ってきた title がどの粒度の代表点かを推定する（ヒューリスティック）
function levelOf(title, muniNames) {
  const t = toHalf(title);
  if (/^(北海道|東京都|京都府|大阪府|.{2,3}県)$/.test(t)) return 'prefecture';
  if (muniNames.has(t)) return 'municipality';
  if (/\d+号$/.test(t)) return 'go';
  if (/\d+番地?$/.test(t)) return 'banchi';
  return 'town';
}

function classify(input, features, muni) {
  const muniNames = new Set([...muni.values()].map((v) => v.pref + v.city));
  // 今回の応答では施設名の候補だけ addressCode が空でなかった（公式な定義は未確認）
  const addr = features.filter((f) => f.properties.addressCode === '');
  const others = features.filter((f) => f.properties.addressCode !== '');
  const candidates = addr.map((f) => ({
    title: f.properties.title,
    lon: f.geometry.coordinates[0],
    lat: f.geometry.coordinates[1],
    level: levelOf(f.properties.title, muniNames),
  }));
  let status = 'matched';
  if (candidates.length === 0) status = 'not_found';
  else if (candidates.length > 1) status = 'ambiguous';
  else if (!['go', 'banchi'].includes(candidates[0].level)) status = 'coarse';
  return { input, status, candidates, otherTitles: others.map((f) => f.properties.title) };
}

function reverseCheck(candidate, reverse, muni) {
  const r = reverse.results;
  if (!r) return { consistent: false, reason: 'no_address' }; // 海上・国外など
  const m = muni.get(String(Number(r.muniCd))); // "08220" は muni.js では "8220"
  if (!m) return { consistent: false, reason: 'unknown_muniCd', muniCd: r.muniCd };
  return {
    consistent: toHalf(candidate.title).startsWith(m.pref + m.city),
    muniCd: r.muniCd, pref: m.pref, city: m.city, lv01Nm: r.lv01Nm,
  };
}

async function getJson(url) {
  const res = await fetch(url, { headers: { 'User-Agent': UA } });
  if (!res.ok) throw new Error(`HTTP ${res.status}: ${url}`);
  return res.json();
}

if (process.argv[2] === '--offline') {
  const raw = (n) => readFile(new URL(`./raw/${n}`, import.meta.url), 'utf8');
  const muni = parseMuni(await raw('muni.js'));
  const cases = [
    ['s01', '東京都千代田区永田町1-7-1', 'r01'],
    ['s05', '永田町1-7-1'],
    ['s07', '埼玉県浦和市高砂3-15-1', 'r05'],
    ['s10', '府中市'],
    ['s11', ''],
  ];
  for (const [file, input, rev] of cases) {
    const result = classify(input, JSON.parse(await raw(`${file}.txt`)), muni);
    if (rev && result.candidates.length === 1) {
      result.reverse = reverseCheck(result.candidates[0], JSON.parse(await raw(`${rev}.txt`)), muni);
    }
    console.log(JSON.stringify(result));
  }
} else {
  const input = process.argv[2];
  const muni = parseMuni(await (await fetch(MUNI, { headers: { 'User-Agent': UA } })).text());
  const result = classify(input, await getJson(SEARCH + encodeURIComponent(input)), muni);
  if (result.status === 'matched') {
    const c = result.candidates[0];
    result.reverse = reverseCheck(c, await getJson(`${REVERSE}?lat=${c.lat}&lon=${c.lon}`), muni);
  }
  result.retrievedAt = new Date().toISOString();
  console.log(JSON.stringify(result, null, 2));
}

$ node gsi-check.mjs --offline
{"input":"東京都千代田区永田町1-7-1","status":"matched",
 "candidates":[{"title":"東京都千代田区永田町一丁目７番","lon":139.744385,"lat":35.677414,"level":"banchi"}],
 "reverse":{"consistent":true,"muniCd":"13101","pref":"東京都","city":"千代田区","lv01Nm":"永田町一丁目"}}
{"input":"永田町1-7-1","status":"ambiguous",
 "candidates":[{"title":"埼玉県秩父市永田町１番７号","level":"go"},{"title":"東京都千代田区永田町一丁目７番","level":"banchi"},{"title":"静岡県富士市永田町一丁目７番地","level":"banchi"}]}
{"input":"埼玉県浦和市高砂3-15-1","status":"coarse",
 "candidates":[{"title":"埼玉県","lon":139.649017,"lat":35.857033,"level":"prefecture"}],
 "reverse":{"consistent":false,"muniCd":"11107","pref":"埼玉県","city":"さいたま市浦和区","lv01Nm":"高砂三丁目"}}
{"input":"府中市","status":"ambiguous",
 "candidates":[{"title":"東京都府中市","level":"municipality"},{"title":"広島県府中市","level":"municipality"}],
 "otherTitles":["府中市役所","府中市役所","府中市民病院","府中市美術館","府中市郷土の森博物館"]}
{"input":"","status":"not_found","candidates":[],"otherTitles":[]}

- 住所の確定は geocode_address の status が matched かつ reverse.consistent が true のときだけ
- ambiguous は候補を番号付きで示して止まる。候補から推測で選ばない
- coarse / not_found は「旧地名・誤記の可能性」として差し戻す。座標が近くても採用しない
- 元の住所文字列は書き換えず、正規化後の表記と座標は別の列に入れる