app/live_layers.py

@@ -54,6 +54,13 @@ TITILER_COG_TILES = f"{TITILER_PUBLIC_BASE}/cog/tiles/WebMercatorQuad/{{z}}/{{x}
 SENTINEL1_TTL = 20 * 60  # 15–30 min quota-friendly window
 SENTINEL1_ATTRIBUTION = "Copernicus Sentinel-1 / Microsoft Planetary Computer"
 
+# GPSJAM (John Wiseman / ADS-B Exchange): daily H3 hexes of aircraft nav
+# accuracy. Hexes are published as a gzip CSV at a stable per-date URL, soon
+# after midnight UTC. Red/yellow != proven jamming.
+GPSJAM_BASE = "https://gpsjam.org"
+GPSJAM_RES = 4
+GPSJAM_TTL = 3600.0  # 1h — whole-world layer, fetched once per day effectively
+
 IEM_NEXRAD = "https://mesonet.agron.iastate.edu/cache/tile.py/1.0.0/nexrad-n0q/{z}/{x}/{y}.png"
 GIBS_THERMAL = (
     "https://gibs.earthdata.nasa.gov/wmts/epsg3857/best/"
@@ -135,6 +142,12 @@ def overlay_catalog() -> dict:
         "vessels": {"id": "vessels", "kind": "points", "endpoint": "/api/vessels"},
         "trains": {"id": "trains", "kind": "points", "endpoint": "/api/trains"},
         "storms": {"id": "storms", "kind": "points", "endpoint": "/api/storms"},
+        "gpsjam": {
+            "id": "gpsjam",
+            "kind": "geojson",
+            "endpoint": "/api/map/gpsjam",
+            "attribution": "GPSJAM / John Wiseman / ADS-B Exchange",
+        },
     }
 
 
@@ -1283,3 +1296,79 @@ async def fetch_sentinel1(bbox: str) -> dict | None:
         }
 
     return await _ttl_get(key, float(SENTINEL1_TTL), _load)
+# ── GPSJAM ──────────────────────────────────────────────────────────────────
+
+
+def gpsjam_level(percent_bad: float) -> str:
+    """Map a denoised bad-aircraft percentage to GPSJAM's three tiers."""
+    if percent_bad > 10.0:
+        return "high"
+    if percent_bad > 2.0:
+        return "medium"
+    return "low"
+
+
+def gpsjam_csv_to_geojson(text: str) -> dict:
+    """Convert a GPSJAM daily CSV to a world FeatureCollection of hex polygons.
+
+    Rows are ``hex,count_good_aircraft,count_bad_aircraft``. The interference
+    percentage uses GPSJAM's published denoise formula
+    ``100 * (bad - 1) / (good + bad)``; hexes with zero bad aircraft are the
+    "normal" background and are dropped (the base map already shows nothing).
+    """
+    import csv
+    import io
+
+    import h3
+
+    features = []
+    for row in csv.DictReader(io.StringIO(text)):
+        hex_id = (row.get("hex") or "").strip()
+        if not hex_id:
+            continue
+        try:
+            good = int(row.get("count_good_aircraft") or 0)
+            bad = int(row.get("count_bad_aircraft") or 0)
+        except (TypeError, ValueError):
+            continue
+        if bad < 1:
+            continue
+        denom = good + bad
+        percent = 100.0 * (bad - 1) / denom if denom > 0 else 0.0
+        try:
+            # h3 returns (lat, lng); GeoJSON needs (lng, lat) closed rings.
+            ring = [[lng, lat] for lat, lng in h3.cell_to_boundary(hex_id)]
+        except Exception:  # malformed/unknown cell id — skip
+            continue
+        ring.append(ring[0])
+        features.append({
+            "type": "Feature",
+            "geometry": {"type": "Polygon", "coordinates": [ring]},
+            "properties": {
+                "level": gpsjam_level(percent),
+                "percent_bad": round(percent, 2),
+                "good": good,
+                "bad": bad,
+                "hex": hex_id,
+            },
+        })
+    return {"type": "FeatureCollection", "features": features}
+
+
+async def fetch_gpsjam(date: str) -> dict:
+    """Fetch + convert one GPSJAM daily hex layer (whole world, 1h TTL)."""
+    url = f"{GPSJAM_BASE}/data/{date}-h3_{GPSJAM_RES}.csv"
+
+    async def _load():
+        if _http is None:
+            async with httpx.AsyncClient(
+                timeout=_HTTP_TIMEOUT, follow_redirects=True, headers=_headers(),
+            ) as client:
+                resp = await client.get(url)
+                resp.raise_for_status()
+                return gpsjam_csv_to_geojson(resp.text)
+        resp = await _http.get(url)
+        resp.raise_for_status()
+        return gpsjam_csv_to_geojson(resp.text)
+
+    return await _ttl_get(f"gpsjam:{date}", GPSJAM_TTL, _load)

app/main.py

@@ -14,6 +14,7 @@ from __future__ import annotations
 import asyncio
 import json
 import logging
+import re
 from contextlib import asynccontextmanager
 from datetime import datetime, timedelta, timezone
 from decimal import Decimal
@@ -21,6 +22,7 @@ from pathlib import Path
 from typing import NoReturn
 from uuid import UUID
 
+import httpx
 import structlog
 from fastapi import BackgroundTasks, FastAPI, HTTPException, Query, WebSocket, WebSocketDisconnect
 from fastapi.middleware.gzip import GZipMiddleware
@@ -53,9 +55,9 @@ from keystore import KeyFormatError, delete_key, list_keys, set_key
 from settings_store import SettingsError, get_app_settings, list_models, set_summary_model
 from live_layers import (
     fetch_aircraft, fetch_fire_incidents, fetch_fire_perimeters,
-    fetch_planespotters_photo, fetch_radar_meta, fetch_sentinel1, fetch_storms,
-    fetch_trains, fetch_vessels, fetch_weather_alerts, overlay_catalog,
-    parse_bbox, UpstreamRateLimited,
+    fetch_gpsjam, fetch_planespotters_photo, fetch_radar_meta, fetch_sentinel1,
+    fetch_storms, fetch_trains, fetch_vessels, fetch_weather_alerts,
+    overlay_catalog, parse_bbox, UpstreamRateLimited,
 )
 
 logging.basicConfig(level=logging.INFO)
@@ -1682,6 +1684,41 @@ async def list_storms():
         _upstream_or_502(exc, "storms")
 
 
+_GPSJAM_DATE = re.compile(r"^\d{4}-\d{2}-\d{2}$")
+
+
+@app.get("/api/map/gpsjam")
+async def map_gpsjam(
+    date: str | None = Query(None, description="YYYY-MM-DD (default: yesterday UTC)"),
+):
+    """GPSJAM daily GPS-interference hex layer (whole world, GeoJSON).
+
+    Red/yellow hexes correlate with suspected jamming but are NOT proof of it.
+    Fetched once per day from gpsjam.org (ADS-B Exchange data) and cached 1h.
+    """
+    target = date
+    if target is None:
+        target = (datetime.now(timezone.utc) - timedelta(days=1)).strftime("%Y-%m-%d")
+    if not _GPSJAM_DATE.match(target):
+        raise HTTPException(422, "date must be YYYY-MM-DD")
+    try:
+        fc = await fetch_gpsjam(target)
+    except httpx.HTTPStatusError as exc:
+        if exc.response.status_code == 404:
+            return JSONResponse(
+                {"error": "unavailable", "href": "https://gpsjam.org/",
+                 "date": target},
+            )
+        _upstream_or_502(exc, "gpsjam")
+    except Exception as exc:
+        _upstream_or_502(exc, "gpsjam")
+    if not fc.get("features"):
+        return JSONResponse(
+            {"error": "unavailable", "href": "https://gpsjam.org/", "date": target},
+        )
+    return overlay_json(fc, 3600)
+
+
 @app.get("/api/map/times")
 async def map_layer_times(
     layer: str = Query(..., description="GIBS layer identifier, e.g. VIIRS_SNPP_CorrectedReflectance_TrueColor"),

app/requirements.txt

@@ -12,3 +12,4 @@ python-dateutil>=2.9
 structlog>=24.4
 websockets>=14
 cachetools>=5.5
+h3>=4.0

tests/test_gpsjam.py

@@ -0,0 +1,150 @@
+"""GPSJAM GPS-interference overlay: level mapping, CSV→GeoJSON, API contract."""
+
+import asyncio
+
+import httpx
+
+from live_layers import gpsjam_csv_to_geojson, gpsjam_level, overlay_catalog, _cache
+from main import app
+
+BASE = "http://test"
+
+# A valid H3 resolution-4 cell id (the payload hex column carries these).
+HEX_A = "8400c57ffffffff"
+
+CSV = (
+    "hex,count_good_aircraft,count_bad_aircraft\n"
+    f"{HEX_A},0,20\n"        # 100*(20-1)/20 = 95  -> high
+    f"{HEX_A},8,2\n"         # 100*(2-1)/10  = 10  -> medium
+    f"{HEX_A},98,2\n"        # 100*(2-1)/100 = 1   -> low
+    f"{HEX_A},100,0\n"       # bad == 0            -> dropped
+)
+
+
+async def _get(path: str) -> httpx.Response:
+    transport = httpx.ASGITransport(app=app)
+    async with httpx.AsyncClient(transport=transport, base_url=BASE) as client:
+        return await client.get(path)
+
+
+def test_gpsjam_level_thresholds():
+    assert gpsjam_level(0.0) == "low"
+    assert gpsjam_level(2.0) == "low"
+    assert gpsjam_level(2.1) == "medium"
+    assert gpsjam_level(10.0) == "medium"
+    assert gpsjam_level(10.1) == "high"
+    assert gpsjam_level(95.0) == "high"
+
+
+def test_gpsjam_csv_to_geojson_levels_and_drop_zero_bad():
+    fc = gpsjam_csv_to_geojson(CSV)
+    assert fc["type"] == "FeatureCollection"
+    assert len(fc["features"]) == 3  # bad==0 row dropped
+    levels = [f["properties"]["level"] for f in fc["features"]]
+    assert levels == ["high", "medium", "low"]
+    for f in fc["features"]:
+        geom = f["geometry"]
+        assert geom["type"] == "Polygon"
+        ring = geom["coordinates"][0]
+        assert len(ring) == 7  # 6 verts + closing point
+        assert ring[0] == ring[-1]
+        assert f["properties"]["hex"] == HEX_A
+        assert set(f["properties"]).issuperset({"level", "percent_bad", "good", "bad", "hex"})
+
+
+def test_gpsjam_csv_skips_malformed_rows():
+    bad_csv = "hex,count_good_aircraft,count_bad_aircraft\n" \
+              ",1,5\n" \
+              f"{HEX_A},x,5\n" \
+              f"{HEX_A},1,notanint\n" \
+              "not_a_cell,1,5\n"
+    fc = gpsjam_csv_to_geojson(bad_csv)
+    assert fc["features"] == []
+
+
+def test_overlay_catalog_has_gpsjam_stub():
+    entry = overlay_catalog()["gpsjam"]
+    assert entry["kind"] == "geojson"
+    assert entry["endpoint"] == "/api/map/gpsjam"
+    assert "GPSJAM" in entry["attribution"]
+
+
+def test_map_gpsjam_returns_featurecollection(monkeypatch):
+    async def fake_fetch(date):
+        return {"type": "FeatureCollection", "features": [{"type": "Feature"}]}
+
+    monkeypatch.setattr("main.fetch_gpsjam", fake_fetch)
+    resp = asyncio.run(_get("/api/map/gpsjam?date=2026-08-28"))
+    assert resp.status_code == 200
+    assert resp.json()["type"] == "FeatureCollection"
+    assert "max-age" in (resp.headers.get("cache-control") or "").lower()
+
+
+def test_map_gpsjam_rejects_bad_date():
+    resp = asyncio.run(_get("/api/map/gpsjam?date=08-28-2026"))
+    assert resp.status_code == 422
+
+
+def test_map_gpsjam_unavailable_on_404(monkeypatch):
+    import httpx as _httpx
+
+    async def fake_fetch(date):
+        exc = _httpx.HTTPStatusError(
+            "404", request=_httpx.Request("GET", "http://x"), response=_httpx.Response(404)
+        )
+        raise exc
+
+    monkeypatch.setattr("main.fetch_gpsjam", fake_fetch)
+    resp = asyncio.run(_get("/api/map/gpsjam?date=2026-08-28"))
+    assert resp.status_code == 200
+    body = resp.json()
+    assert body["error"] == "unavailable"
+    assert body["href"] == "https://gpsjam.org/"
+
+
+def test_map_gpsjam_unavailable_on_empty_features(monkeypatch):
+    async def fake_fetch(date):
+        return {"type": "FeatureCollection", "features": []}
+
+    monkeypatch.setattr("main.fetch_gpsjam", fake_fetch)
+    resp = asyncio.run(_get("/api/map/gpsjam?date=2026-08-28"))
+    assert resp.status_code == 200
+    assert resp.json()["error"] == "unavailable"
+
+
+def test_fetch_gpsjam_hits_http_once_within_ttl(monkeypatch):
+    _cache.clear()
+    hits = {"n": 0}
+
+    class FakeResp:
+        text = CSV
+
+        def raise_for_status(self):
+            pass
+
+    class FakeClient:
+        def __init__(self, **kw):
+            pass
+
+        async def __aenter__(self):
+            return self
+
+        async def __aexit__(self, *exc):
+            return False
+
+        async def get(self, url):
+            hits["n"] += 1
+            assert url == "https://gpsjam.org/data/2026-08-28-h3_4.csv"
+            return FakeResp()
+
+    monkeypatch.setattr("live_layers.httpx.AsyncClient", FakeClient)
+    monkeypatch.setattr("live_layers._http", None)
+
+    from live_layers import fetch_gpsjam
+
+    fc1 = asyncio.run(fetch_gpsjam("2026-08-28"))
+    fc2 = asyncio.run(fetch_gpsjam("2026-08-28"))
+    assert len(fc1["features"]) == 3
+    assert fc2 == fc1
+    assert hits["n"] == 1
+    _cache.clear()