Switch /api/reverse/<lat>/<lon> elevation source from Valhalla to planet-DEM

Per OFFROUTE-ARCHITECTURE.md §9 ("planet-dem.pmtiles as single elevation
source"). The bundle endpoint previously called Valhalla /height, which only
has 48 Idaho HGT tiles; it now reads the planet-scale Terrarium PMTiles that
already back the frontend hillshade and contours.

- dem.py: add DEMReader.sample_point(lat, lon) — one z12 tile (LRU-cached),
  Web-Mercator pixel index, None outside the +/-85.05 pole cap or when untiled.
- netsyms_api.py: module-level DEMReader singleton (lazy mmap, None if init
  fails); _reverse_elevation now calls _DEM.sample_point; drop the Valhalla
  HTTP call and _VALHALLA_HEIGHT_URL.
- tests: DEM-mock and DEM-unavailable cases; EXPECTED_KEYS derives from
  _BUNDLE_KEYS. All 9 tests pass.

Verified live: Boise 824m, London 8m, Tokyo 35m, Yosemite 2804m, pole -> None.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lib/netsyms_api.py

@@ -17,6 +17,7 @@ from . import netsyms
 from . import address_book
 from . import nav_tools
 from .geocode import PHOTON_URL
+from .offroute.dem import DEMReader
 from .utils import setup_logging
 
 logger = setup_logging('recon.netsyms_api')
@@ -137,12 +138,11 @@ def api_reverse():
 #
 #  Sibling to the query-string /api/reverse above; that route is unchanged.
 #  Every component is sourced from localhost only (Photon, timezones.sqlite,
-#  in-process landclass/PostGIS, Valhalla). Each lookup is independent: a
-#  component failure logs a warning and yields null — never a 5xx.
+#  in-process landclass/PostGIS, planet-DEM PMTiles). Each lookup is
+#  independent: a component failure logs a warning and yields null — never 5xx.
 # ─────────────────────────────────────────────────────────────────────────
 
 _TZ_DB_PATH = "/mnt/nav/sources/timezones.sqlite"
-_VALHALLA_HEIGHT_URL = "http://localhost:8002/height"
 
 # Full bundle cache: key=(round(lat,4), round(lon,4)) -> dict. ~10k entries, 24h TTL.
 _REVERSE_BUNDLE_CACHE = TTLCache(maxsize=10_000, ttl=86_400)
@@ -151,6 +151,14 @@ _REVERSE_BUNDLE_LOCK = threading.Lock()
 _BUNDLE_KEYS = ('name', 'city', 'county', 'state', 'country',
                 'postal_code', 'timezone', 'landclass', 'elevation_m')
 
+# planet-DEM elevation source (single PMTiles, replaces Valhalla /height).
+# Instantiated once at import; the underlying mmap is lazy. None if unavailable.
+try:
+    _DEM = DEMReader()
+except Exception as e:  # pragma: no cover - depends on PMTiles availability
+    logger.warning("DEMReader unavailable, elevation will be null: %s", e)
+    _DEM = None
+
 
 def _spatialite_blob_to_wkb(blob):
     """Recover standard WKB from a SpatiaLite geometry BLOB.
@@ -224,16 +232,12 @@ def _reverse_landclass(lat, lon):
 
 
 def _reverse_elevation(lat, lon):
-    """Elevation in metres from local Valhalla /height. None on failure."""
-    import requests as http_requests
-    resp = http_requests.post(
-        _VALHALLA_HEIGHT_URL,
-        json={"shape": [{"lat": lat, "lon": lon}]},
-        timeout=10,
-    )
-    resp.raise_for_status()
-    heights = resp.json().get("height", [])
-    return heights[0] if heights else None
+    """Elevation in metres from the planet-DEM PMTiles — the single elevation
+    source per OFFROUTE-ARCHITECTURE.md §9. None on failure, on untiled points
+    (e.g. true ocean), or if DEMReader could not be initialized at startup."""
+    if _DEM is None:
+        return None
+    return _DEM.sample_point(lat, lon)
 
 
 @geocode_bp.route('/api/reverse/<lat>/<lon>')

lib/offroute/dem.py

@@ -159,6 +159,27 @@ class DEMReader:
         
         return elevation, metadata
 
+    def sample_point(self, lat: float, lon: float) -> Optional[float]:
+        """Return elevation in meters at a single point, or None if untiled.
+
+        Reads one z12 Terrarium tile (LRU-cached) and indexes the matching
+        pixel. Sub-ms warm, ~15 ms cold per tile via NFS. Returns None when the
+        tile is absent (e.g. true ocean nodata) or lat is outside the
+        Web-Mercator pole cap (~+/-85.05 deg).
+        """
+        if not -85.05112878 <= lat <= 85.05112878:
+            return None
+        n = 2 ** ZOOM_LEVEL
+        fx = (lon + 180.0) / 360.0 * n
+        fy = (1.0 - math.asinh(math.tan(math.radians(lat))) / math.pi) / 2.0 * n
+        tx, ty = int(fx), int(fy)
+        tile = self._decode_tile(ZOOM_LEVEL, tx, ty)
+        if tile is None:
+            return None
+        row = min(TILE_SIZE - 1, int((fy - ty) * TILE_SIZE))
+        col = min(TILE_SIZE - 1, int((fx - tx) * TILE_SIZE))
+        return float(tile[row, col])
+
     def pixel_to_latlon(self, row: int, col: int, metadata: dict) -> Tuple[float, float]:
         """Convert pixel coordinates to lat/lon."""
         lat = metadata["origin_lat"] + row * metadata["pixel_size_lat"]

lib/reverse_bundle_test.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python3
 """Tests for the /api/reverse/<lat>/<lon> enrichment bundle (lib.netsyms_api).
 
-Photon/Valhalla/landclass are mocked so the suite runs without live services;
+Photon/DEM/landclass are mocked so the suite runs without live services;
 one timezone test exercises the real SpatiaLite DB when it is present. Plain
 asserts + a __main__ runner, matching the rest of lib/*_test.py.
 """
@@ -15,8 +15,7 @@ sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
 from flask import Flask
 from lib import netsyms_api
 
-EXPECTED_KEYS = {'name', 'city', 'county', 'state', 'country',
-                 'postal_code', 'timezone', 'landclass', 'elevation_m'}
+EXPECTED_KEYS = set(netsyms_api._BUNDLE_KEYS)
 
 
 def _client():
@@ -124,6 +123,40 @@ def test_real_timezone_db():
     print("  PASS: real timezones.sqlite point-in-polygon")
 
 
+def test_elevation_from_dem_reader_mock():
+    # elevation_m comes from DEMReader.sample_point (not Valhalla); other
+    # components stubbed to null so the bundle is hermetic.
+    _clear_cache()
+    fake_dem = mock.Mock()
+    fake_dem.sample_point.return_value = 824
+    with mock.patch.object(netsyms_api, '_DEM', fake_dem), \
+         mock.patch.object(netsyms_api, '_reverse_photon', return_value={}), \
+         mock.patch.object(netsyms_api, '_reverse_timezone', return_value=None), \
+         mock.patch.object(netsyms_api, '_reverse_landclass', return_value=None):
+        resp = _client().get('/api/reverse/43.6150/-116.2023')
+    assert resp.status_code == 200, resp.status_code
+    data = resp.get_json()
+    assert set(data.keys()) == EXPECTED_KEYS
+    assert data['elevation_m'] == 824, data['elevation_m']
+    fake_dem.sample_point.assert_called_once()
+    print("  PASS: elevation_m sourced from DEMReader.sample_point")
+
+
+def test_elevation_dem_unavailable():
+    # DEMReader failed to init at startup (_DEM is None) -> elevation_m null, 200.
+    _clear_cache()
+    with mock.patch.object(netsyms_api, '_DEM', None), \
+         mock.patch.object(netsyms_api, '_reverse_photon', return_value={}), \
+         mock.patch.object(netsyms_api, '_reverse_timezone', return_value=None), \
+         mock.patch.object(netsyms_api, '_reverse_landclass', return_value=None):
+        resp = _client().get('/api/reverse/43.6150/-116.2023')
+    assert resp.status_code == 200, resp.status_code
+    data = resp.get_json()
+    assert set(data.keys()) == EXPECTED_KEYS
+    assert data['elevation_m'] is None
+    print("  PASS: DEMReader unavailable -> elevation_m null, still 200")
+
+
 if __name__ == '__main__':
     print("Running reverse-bundle tests...")
     test_happy_path()
@@ -133,4 +166,6 @@ if __name__ == '__main__':
     test_invalid_input_400()
     test_cache_hit_serves_without_recompute()
     test_real_timezone_db()
+    test_elevation_from_dem_reader_mock()
+    test_elevation_dem_unavailable()
     print("All tests passed.")