Draw aids to navigation as buoys

A buoy, beacon, RACON, light or IALA mark in the vessel feed was drawn
as a ship. A vessel record whose type names one, or whose MMSI is an
aid-to-navigation station's (99MIDxxxx), is now isAidToNavigation and
vesselModelSpec draws it as the fleet set's buoy of its mark (cardinal
N/E/S/W, port or starboard hand, safe water, isolated danger, special
mark; a red can when the type names no mark), at its built size and
flagged fixed so its model does not turn to a heading. Its icon is a
disc instead of a chevron.

AISStream now subscribes to AidsToNavigationReport by default, and the
server names each report's aid type code (0 to 31) as its kind instead
of reading it as a ship type.

.env.example

@@ -176,7 +176,7 @@ VITE_AIS_LIVE_LABEL_MAX_ROWS=900
 AISSTREAM_API_KEY=
 # Optional AISStream subscription filters.
 # AISSTREAM_BOUNDING_BOXES=[[[-90,-180],[90,180]]]
-# AISSTREAM_MESSAGE_TYPES=PositionReport,StandardClassBPositionReport,ExtendedClassBPositionReport,ShipStaticData,StaticDataReport
+# AISSTREAM_MESSAGE_TYPES=PositionReport,StandardClassBPositionReport,ExtendedClassBPositionReport,ShipStaticData,StaticDataReport,AidsToNavigationReport
 # Feed watchdog: silence (ms) after which the feed is REPORTED stale; the socket
 # is recycled at 2.5x that. Default 120000. The watchdog self-arms only for the
 # default worldwide subscription — a narrow filter above can be legitimately

changelog.d/0000-buoy-models.md

@@ -0,0 +1,7 @@
+- Draw aids to navigation as buoys instead of ships: a buoy, beacon, RACON,
+  light or mark from the vessel feed (or any AIS station numbered 99MIDxxxx)
+  is now the fleet set's buoy of its IALA mark (cardinal, port or starboard
+  hand, safe water, isolated danger or special mark), standing still with no
+  heading, and its icon is a disc rather than a chevron. AISStream now
+  subscribes to aid-to-navigation reports and names each by its kind of mark
+  (samehkhamis, #0000).

docs/CURRENT-STATE.md

@@ -7430,7 +7430,7 @@ pins and share links already supply complete boxes.
   30-second backoff ahead of the current clock are ignored. A smaller rollback
   can retain a bounded retry delay of up to 30 seconds.
 - Commercial and military aircraft use the same high-level FLEET model regime: 2D billboards when zoomed out, optional glTF models when closer, controlled by the DISPLAY rail `3D` toggle and `Proximity` / `All` modes. Every model is one of the project's procedural fleet models (`public/models/fleet/`, MIT, 122 GLBs, about 2 MB in all; `public/models/README.md`), chosen per aircraft by `aircraftModelSpec` (`src/data/fleetModels.js`): the first of its ICAO type's callsign rules in `types.json` (`aircraft_callsign`) its callsign matches, else its type's entry, else the model of its `classifyAircraft` class for a type the map lacks, else its ADS-B emitter category's, else the default airliner. It is drawn LIFE SIZE: the type's published length over the model's built length (`src/layers/flights/modelSpec.js`, shared by Flights, Military Flights and Local ADS-B), and a grounded aircraft stands the model's scaled clearance above the ground. An airport ground vehicle (feed type `ZVEH`) is a fire truck (`FIRE…`), pushback tug (`PUSH…`, `TUG…`), van (`DEICER…`, `SQUID…`, `SQB…`) or else a car by its callsign, and a ground station (`GRND`) is an 11.8 m radio mast; these models (catalog category `other`) are drawn at their built size, and such a contact with no altitude stands on the ground instead of at the airborne default (`src/layers/flights/records.js`). `classifyAircraft` still picks the 2D icons. The whole set loads once, up front, when a layer that draws it starts (`loadFleetModelSet`, which logs `[Fleet] N/122 models (X MB) loaded in N ms`); models are built from those bytes, never fetched mid-session, and an aircraft stays its billboard until the set has loaded. Every aircraft model draws its mesh's own colours (`aircraftModelBlend`, `src/data/aircraftModelLighting.js`): Cesium's `ColorBlendMode.HIGHLIGHT` with white, in Flights, Military Flights and Local ADS-B alike; the tracked colour (cyan, or amber in Military Flights) and the emergency red multiply into the mesh, so its paint still shows. IR boost draws them flat white (`MIX` at `1.0`). Under NVG/FLIR (map preset or Cockpit vision) models render unlit flat-white at full alpha and scene fog is disabled (fog otherwise blacks out distant models with the globe hidden); state restores on exit.
-- Vessels, Transit and Rail draw fleet models under the same DISPLAY rail `3D` toggle, at the same altitude ceiling, caps and add/keep radii as the aircraft (`FLEET_MODEL_POLICY`, `src/layers/flights/policy.js`; `createFleetModelLayer`, `src/data/fleetModelInstances.js`). A vessel's model follows its AIS ship type and is drawn at its reported length and beam (AIS static dimensions A+B and C+D, now carried on vessel rows as `length` and `beam`), standing at the sea surface, heading by true heading then course. A transit vehicle's model follows its layer mode (bus, tram, subway, rail or ferry; a vehicle of `unknown` mode keeps its icon), a train's its rail category and mode (rail, metro or tram). Neither the transit nor the rail sources carry a GTFS `route_type` or a finer mode (monorail, gondola, funicular, cable car), so the set's models for those and their `transit.elevation` lifts are not reached by any live source today. Both stand on the road or rail top they are drawn on, without the 1.5 m `GROUND_FLOOR_LIFT_M` their icons carry, and are painted in their mode or category colour where the model's `_TINT` attribute marks it. A vessel model is clipped at its waterline (one clipping plane per model, at the model origin's horizontal plane), so its hull below the water never shows through a plain globe, which Cesium does not depth-test models against. Under the NVG/FLIR styles (the Flights `irBoost` parameter) these models render unlit flat white, as aircraft models do. Each vehicle's icon stays the visual until its model is loaded, ready and placed; a model is picked as its icon is, and a vehicle drawn as its model keeps its selection card and its place in the detection overlay.
+- Vessels, Transit and Rail draw fleet models under the same DISPLAY rail `3D` toggle, at the same altitude ceiling, caps and add/keep radii as the aircraft (`FLEET_MODEL_POLICY`, `src/layers/flights/policy.js`; `createFleetModelLayer`, `src/data/fleetModelInstances.js`). A vessel's model follows its AIS ship type and is drawn at its reported length and beam (AIS static dimensions A+B and C+D, now carried on vessel rows as `length` and `beam`), standing at the sea surface, heading by true heading then course. An aid to navigation is not a hull: a vessel record whose type names a buoy, beacon, mark, RACON or light, or whose MMSI is an aid-to-navigation station's (`99MIDxxxx`), is `isAidToNavigation` (`src/data/vesselTypes.js`) and is drawn as the set's `buoys` model of the IALA mark its type names (`aidToNavigationModel`, `src/data/fleetModels.js`: cardinal N/E/S/W, port or starboard hand, preferred channel by its side, safe water, isolated danger, special mark; a beacon, light, light vessel, RACON or reference point with no mark of its own is the special mark), else a red can (`DEFAULT_AID_MODEL`), at its built size and facing north whatever heading it reports. Its icon is a bone-white ringed disc instead of a chevron, never rotated. AISStream subscribes to `AidsToNavigationReport` (message 21) by default, and the server names each report's aid type code (0 to 31) as its kind (`aidToNavigationTypeName`: `20` is `Cardinal Mark N`) rather than reading it as a ship type. A transit vehicle's model follows its layer mode (bus, tram, subway, rail or ferry; a vehicle of `unknown` mode keeps its icon), a train's its rail category and mode (rail, metro or tram). Neither the transit nor the rail sources carry a GTFS `route_type` or a finer mode (monorail, gondola, funicular, cable car), so the set's models for those and their `transit.elevation` lifts are not reached by any live source today. Both stand on the road or rail top they are drawn on, without the 1.5 m `GROUND_FLOOR_LIFT_M` their icons carry, and are painted in their mode or category colour where the model's `_TINT` attribute marks it. A vessel model is clipped at its waterline (one clipping plane per model, at the model origin's horizontal plane), so its hull below the water never shows through a plain globe, which Cesium does not depth-test models against. Under the NVG/FLIR styles (the Flights `irBoost` parameter) these models render unlit flat white, as aircraft models do. Each vehicle's icon stays the visual until its model is loaded, ready and placed; a model is picked as its icon is, and a vehicle drawn as its model keeps its selection card and its place in the detection overlay.
 - **Aircraft models skip Cesium's dynamic environment map (2026-10-24).** Flights, Military Flights and Local ADS-B pass `environmentMapOptions: AIRCRAFT_ENVIRONMENT_MAP_OPTIONS` (`{ enabled: false }`, `src/data/aircraftModelLighting.js`) to every drawn model. Otherwise each `Model` renders the sky around it and reads it back from the GPU (`readPixels`) when it is first placed, and again whenever it moves more than 1 km, the scene's atmosphere settings change, or (under sunlight dynamic lighting) an hour of scene time passes (`DynamicEnvironmentMapManager`, Cesium 1.138). The models are lit from Cesium's default spherical harmonics instead, with no specular environment map, so the sky's model-lighting cube map no longer reaches aircraft. `src/data/aircraftModelLighting.test.mjs` pins the option at every drawn model call; every model is built from the fleet set loaded up front, so there is no separate preload.
 - The DISPLAY-rail `3D` toggle is the user-facing activation path for both aircraft layers. Their small approved GLBs build their render resources without Cesium's frame-spread job queue, preventing continuous Photorealistic 3D Tiles streaming from starving model readiness; model caps, tracking, camera, and fallback billboards are unchanged.
 - **The `3D` toggle DEFAULTS ON in `proximity` on a first run.** Proximity is itself the budget — models appear only below `MODEL_ALT_CEIL_M` and only for the nearest `MODEL_MAX` in view — so the default costs nothing at globe scale, and `all` remains a deliberate opt-in. A fresh boot runs NO layer-state restoration (`LayerStateCoordinator.start()` returns early with neither a share payload nor stored state), so four independent initializers decide what a first-run operator sees and must agree: `booleanOption('models3d', 'e', true)` in `src/data/layerState.js`, `_models3dEnabled = true` in BOTH flight layers, `this._models3dEnabled = true` in `src/ui/aircraftDisplay.js`, and the `active` / `visible` classes on `#models3d-toggle` / `#models3d-mode-row` in `index.html`. All four are pinned together in `src/data/layerState.test.mjs`. Explicit state still wins: because the codec omits default-valued options, `models3d: false` is now what travels in a link (`lo=…f.e.0`) and restores OFF at both aircraft layers. **Consequence for returning users:** a stored `gev:layer-state:v2` blob is a FULL options snapshot, so a session that wrote one before this change carries `models3d:false` and keeps 3D off until the operator flips it (or clears the key) — the durable snapshot is treated as the recipient's own state, by design.

public/models/README.md

@@ -19,6 +19,12 @@ How the layers use them:
   type's published length (a vessel to its reported AIS length and beam), so
   every model is drawn life size. Ground objects, balloons and obstacles in
   the `other` category are drawn at the size they are built.
+- An aid to navigation (a vessel record whose type names a buoy, beacon, IALA
+  mark, RACON or light, or whose MMSI is an aid station's `99MIDxxxx`) is
+  drawn as the `buoys` model of its mark (cardinal north, east, south or west,
+  port or starboard hand, safe water, isolated danger, special mark), a red
+  can when its type names no mark, at its built size and with no heading
+  (`vesselModelSpec`, `aidToNavigationModel`).
 - An aircraft model's origin is its axis; it stands that model's scaled
   clearance above the ground. A ship's origin is its waterline, and a transit
   or rail vehicle's the road or rail top (a monorail or gondola is raised by

scripts/package-boundaries.json

@@ -251,6 +251,7 @@
       "src/data/adsbLolFallback.js",
       "src/data/aisStreamAdapter.js",
       "src/data/aisWatchdog.js",
+      "src/data/vesselTypes.js",
       "src/sources/httpBody.js",
       "src/i18n/marker.js",
       "server/providers/acartia.js",
@@ -1514,6 +1515,7 @@
     "exports": ["./layers/flights"],
     "modules": [
       "src/data/fleetModels.js",
+      "src/data/vesselTypes.js",
       "src/data/fleetTrailAnchors.js",
       "src/data/fleetModelInstances.js",
       "src/data/headingDegrees.js",
@@ -1593,6 +1595,7 @@
       "src/layers/flights/modelSpec.js",
       "src/layers/flights/policy.js",
       "src/data/fleetModels.js",
+      "src/data/vesselTypes.js",
       "src/data/fleetTrailAnchors.js",
       "src/data/fleetModelInstances.js",
       "src/data/headingDegrees.js",
@@ -4817,6 +4820,7 @@
       "src/data/aircraftClass.js",
       "src/data/aircraftEmergency.js",
       "src/data/fleetModels.js",
+      "src/data/vesselTypes.js",
       "src/data/fleetTrailAnchors.js"
     ],
     "external": []
@@ -5207,6 +5211,7 @@
     "exports": ["./layers/transit/standalone"],
     "modules": [
       "src/data/fleetModels.js",
+      "src/data/vesselTypes.js",
       "src/data/aircraftClass.js",
       "src/i18n/marker.js",
       "src/data/fleetModelInstances.js",
@@ -5299,6 +5304,7 @@
     "modules": [
       "src/i18n/marker.js",
       "src/data/fleetModels.js",
+      "src/data/vesselTypes.js",
       "src/data/fleetModelInstances.js",
       "src/data/aircraftClass.js",
       "src/data/aircraftModelLighting.js",

server/providers/vessels/ais-live.js

@@ -27,6 +27,8 @@ const AISSTREAM_DEFAULT_MESSAGE_TYPES = [
   'ExtendedClassBPositionReport',
   'ShipStaticData',
   'StaticDataReport',
+  // Buoys, beacons and other aids to navigation (AIS message 21).
+  'AidsToNavigationReport',
 ];
 // Watchdog budgets (policy lives in src/data/aisWatchdog.js). Silence is
 // REPORTED quickly and ACTED ON slowly: a dead feed must read as dead within

server/providers/vessels/ais-store.js

@@ -1,4 +1,5 @@
 import { isRecognizedAisEnvelope } from '../../../src/data/aisStreamAdapter.js';
+import { aidToNavigationTypeName } from '../../../src/data/vesselTypes.js';
 export const AISSTREAM_CACHE_MAX = 50000;
 export const AISSTREAM_STALE_MS = 30 * 60 * 1000;
 // Per-MMSI recent-path ring buffers (PRD WS-F F3). Float32 lat/lon (~1m
@@ -118,7 +119,12 @@ export function ingestAisStreamEnvelope(envelope) {
     name: vesselNameFromAis(metadata, message, staticData) || `MMSI ${mmsi}`,
     mmsi,
     imo: stringValue(message.ImoNumber ?? message.IMO ?? staticData.imo),
-    type: vesselTypeFromAis(message, staticData),
+    // An aid-to-navigation report's type is the kind of aid (0 to 31), not
+    // a ship type: it is carried as the aid's name ("Cardinal Mark N").
+    type:
+      messageType === 'AidsToNavigationReport'
+        ? aidToNavigationTypeName(message.Type)
+        : vesselTypeFromAis(message, staticData),
     destination: stringValue(message.Destination ?? staticData.destination),
     length: staticData.length ?? null,
     beam: staticData.beam ?? null,

src/data/aisStreamSentinels.test.mjs

@@ -316,3 +316,29 @@ test('a Class B report carries its dimensions in part B', () => {
   assert.equal(row.length, 12);
   assert.equal(row.beam, 4);
 });
+
+test('an aid-to-navigation report is a row named by its kind of aid, not a ship type', () => {
+  assert.equal(
+    ingestAisStreamEnvelope({
+      MessageType: 'AidsToNavigationReport',
+      Message: {
+        AidsToNavigationReport: {
+          UserID: 993672001,
+          Type: 20,
+          Name: 'SF APPROACH N',
+        },
+      },
+      MetaData: {
+        MMSI: '993672001',
+        latitude: 37.79,
+        longitude: -122.52,
+        time_utc: '2026-09-17 20:00:00.000000000 +0000 UTC',
+      },
+    }),
+    true,
+  );
+  const row = rowFor('993672001');
+  assert.equal(row.type, 'Cardinal Mark N');
+  assert.equal(row.name, 'SF APPROACH N');
+  assert.equal(row.speed, null);
+});

src/data/fleetModels.js

@@ -11,6 +11,9 @@
  * vehicle's road or rail top), and is drawn life size: a type's published
  * length over the model's built length is its scale.
  *
+ * An aid to navigation (a buoy, beacon, mark, RACON or light) is drawn as
+ * the set's buoy of its IALA mark, by the mark its type names.
+ *
  * The resolvers are plain functions over the parsed JSON; `loadFleetModelSet`
  * fetches the JSON and every GLB once, up front, so no model is fetched
  * mid-session.
@@ -18,6 +21,7 @@
 
 import { classifyAircraft } from './aircraftClass.js';
 import { FLEET_TRAIL_ANCHORS } from './fleetTrailAnchors.js';
+import { isAidToNavigation } from './vesselTypes.js';
 
 /** Where the model set is served, relative to the application base. */
 export const FLEET_MODEL_BASE = '/models/fleet/';
@@ -84,6 +88,44 @@ const TEXT_SHIP_TYPES = [
   [/pleasure|yacht/i, 37],
 ];
 
+/**
+ * The buoy an aid to navigation is drawn as, by the mark its type names
+ * ("Cardinal Mark N", "Beacon, Port hand", "Safe Water"): the first pattern
+ * that matches. Beacons, lights, RACONs and reference points with no mark of
+ * their own are the special mark.
+ */
+const AID_MODELS = [
+  [/cardinal\b.*\bn(orth)?$/i, 'buoy_cardinal_north'],
+  [/cardinal\b.*\be(ast)?$/i, 'buoy_cardinal_east'],
+  [/cardinal\b.*\bs(outh)?$/i, 'buoy_cardinal_south'],
+  [/cardinal\b.*\bw(est)?$/i, 'buoy_cardinal_west'],
+  [/isolated danger/i, 'buoy_isolated_danger'],
+  [/safe water/i, 'buoy_safe_water'],
+  [/port hand/i, 'buoy_lateral_port'],
+  [/starboard hand/i, 'buoy_lateral_starboard'],
+  [/special mark|light vessel|lanby/i, 'buoy_special'],
+  [
+    /^(beacon|light\b|leading light|racon|reference point|navigation aid)/i,
+    'buoy_special',
+  ],
+];
+
+/** The buoy an aid to navigation whose type names no mark is drawn as. */
+export const DEFAULT_AID_MODEL = 'can_red';
+
+/**
+ * The buoy model of an aid to navigation's type, else undefined when the
+ * type names no mark.
+ * @param {string|null} [type]
+ * @returns {string|undefined}
+ */
+export function aidToNavigationModel(type) {
+  const text = String(type ?? '').trim();
+  for (const [pattern, model] of AID_MODELS)
+    if (pattern.test(text)) return model;
+  return undefined;
+}
+
 /**
  * The model for an aircraft of ICAO type `type` (A320, B738, R44), ADS-B
  * emitter category `category` and callsign `callsign`: the first of the
@@ -397,13 +439,26 @@ export function aircraftModelSpec(
 
 /**
  * The model a vessel is drawn with, from its AIS ship type (a code or a text
- * family), reported length and beam (metres) and name.
+ * family), reported length and beam (metres) and name. An aid to navigation
+ * ({@link isAidToNavigation}: its type names a buoy, beacon, mark, RACON or
+ * light, or its MMSI is an aid's) is the buoy of its mark
+ * ({@link aidToNavigationModel}), else {@link DEFAULT_AID_MODEL}, drawn as
+ * built and flagged `fixed`: it has no heading to turn to.
  * @param {{catalog: object, types: object}} set
- * @param {{type?: string|number|null, length?: number|null,
- *   beam?: number|null, name?: string|null}} vessel
- * @returns {object} {@link fleetModelSpec}
+ * @param {{type?: string|number|null, mmsi?: string|number|null,
+ *   length?: number|null, beam?: number|null, name?: string|null}} vessel
+ * @returns {object} {@link fleetModelSpec}, with `fixed` for an aid
  */
-export function vesselModelSpec(set, { type, length, beam, name } = {}) {
+export function vesselModelSpec(set, { type, mmsi, length, beam, name } = {}) {
+  if (isAidToNavigation({ type, mmsi })) {
+    const model = aidToNavigationModel(type);
+    const known = model && set.catalog[model] ? model : DEFAULT_AID_MODEL;
+    if (set.catalog[known])
+      return Object.freeze({
+        ...fleetModelSpec(set, known, null),
+        fixed: true,
+      });
+  }
   // A beam counts only beside a reported length: a vessel drawn at its type's
   // typical length keeps the model's proportions.
   const reported = hullLength(length ?? undefined);
@@ -460,6 +515,8 @@ export function namedFleetModels(types) {
     transit.default[0],
     ...Object.keys(transit.elevation),
     ...Object.values(CLASS_MODELS),
+    ...AID_MODELS.map(([, model]) => model),
+    DEFAULT_AID_MODEL,
   ]);
 }
 

src/data/fleetModels.test.mjs

@@ -4,7 +4,9 @@ import fs from 'node:fs';
 import path from 'node:path';
 import { fileURLToPath } from 'node:url';
 import {
+  DEFAULT_AID_MODEL,
   FLEET_MODEL_BASE,
+  aidToNavigationModel,
   aircraftModelSpec,
   aisShipTypeCode,
   emitterCategory,
@@ -381,6 +383,58 @@ test('vessel specs read AIS codes and text families, stretched to the reported b
   assert.equal(unknown.scale, 1);
 });
 
+test('aids to navigation are the buoy of the mark their type names', () => {
+  const cases = [
+    ['Cardinal Mark N', 'buoy_cardinal_north'],
+    ['Beacon, Cardinal E', 'buoy_cardinal_east'],
+    ['Cardinal Mark S', 'buoy_cardinal_south'],
+    ['Beacon, Cardinal W', 'buoy_cardinal_west'],
+    ['Port Hand Mark', 'buoy_lateral_port'],
+    ['Beacon, Port hand', 'buoy_lateral_port'],
+    ['Starboard Hand Mark', 'buoy_lateral_starboard'],
+    ['Preferred Channel Starboard hand', 'buoy_lateral_starboard'],
+    ['Safe Water', 'buoy_safe_water'],
+    ['Isolated danger', 'buoy_isolated_danger'],
+    ['Beacon, Special Mark', 'buoy_special'],
+    ['Special Mark', 'buoy_special'],
+    ['Light Vessel / LANBY / Rigs', 'buoy_special'],
+    ['RACON', 'buoy_special'],
+    ['Light, with Sectors', 'buoy_special'],
+    ['Reference point', 'buoy_special'],
+    ['Navigation aid', 'buoy_special'],
+  ];
+  for (const [type, model] of cases) {
+    assert.equal(aidToNavigationModel(type), model, type);
+    assert.ok(catalog[model], model);
+    const spec = vesselModelSpec(set, { type, mmsi: '993672001' });
+    assert.equal(spec.model, model, type);
+    assert.equal(spec.category, 'buoys', type);
+    assert.equal(spec.fixed, true, type);
+    // A buoy is drawn as built, whatever length the report gives.
+    assert.equal(spec.scale, 1, type);
+  }
+  assert.equal(
+    vesselModelSpec(set, { type: 'Safe Water', length: 120, beam: 30 }).scale,
+    1,
+  );
+  // An aid of no stated kind, known only by its MMSI, is the default can.
+  assert.ok(catalog[DEFAULT_AID_MODEL]);
+  const unnamed = vesselModelSpec(set, { type: '', mmsi: '993660123' });
+  assert.equal(unnamed.model, DEFAULT_AID_MODEL);
+  assert.equal(unnamed.fixed, true);
+  assert.equal(aidToNavigationModel('Fixed structure off shore'), undefined);
+  // Vessels, including those that work on buoys, keep their hulls.
+  for (const vessel of [
+    { type: 'Buoy Tender', mmsi: '366999001', length: 60 },
+    { type: '70', mmsi: '366999002' },
+    { type: 'Tug', mmsi: '' },
+  ]) {
+    const spec = vesselModelSpec(set, vessel);
+    assert.notEqual(spec.category, 'buoys', vessel.type);
+    assert.equal(spec.fixed, undefined, vessel.type);
+  }
+});
+
 test('transit specs: rail category and mode, then route type, then mode, then the default', () => {
   assert.deepEqual(resolveTransit(types, { railCategory: 'national' }), {
     model: 'intercity',

src/data/vesselTypes.js

@@ -45,3 +45,82 @@ export function normalizeVesselType(type) {
   if (NUMERIC_TYPE_SPECIALS[code]) return NUMERIC_TYPE_SPECIALS[code];
   return NUMERIC_TYPE_FAMILIES[Math.floor(code / 10)] || 'OTHER';
 }
+
+/**
+ * The kind of aid to navigation an AIS aid-to-navigation report (message 21)
+ * names by its type code, 0 to 31 (ITU-R M.1371, IALA marks): beacons and
+ * floating marks by their cardinal quadrant, lateral side, safe water,
+ * isolated danger or special mark, and the lights, RACONs and reference
+ * points around them. Code 0 names no kind.
+ */
+const AID_TYPE_NAMES = Object.freeze([
+  'Navigation aid',
+  'Reference point',
+  'RACON',
+  'Fixed structure off shore',
+  'Emergency wreck marking buoy',
+  'Light, without sectors',
+  'Light, with sectors',
+  'Leading light front',
+  'Leading light rear',
+  'Beacon, Cardinal N',
+  'Beacon, Cardinal E',
+  'Beacon, Cardinal S',
+  'Beacon, Cardinal W',
+  'Beacon, Port hand',
+  'Beacon, Starboard hand',
+  'Beacon, Preferred channel port hand',
+  'Beacon, Preferred channel starboard hand',
+  'Beacon, Isolated danger',
+  'Beacon, Safe water',
+  'Beacon, Special mark',
+  'Cardinal Mark N',
+  'Cardinal Mark E',
+  'Cardinal Mark S',
+  'Cardinal Mark W',
+  'Port hand Mark',
+  'Starboard hand Mark',
+  'Preferred Channel Port hand',
+  'Preferred Channel Starboard hand',
+  'Isolated danger',
+  'Safe Water',
+  'Special Mark',
+  'Light Vessel / LANBY / Rigs',
+]);
+
+/**
+ * The kind an AIS aid-to-navigation type code names ("19" → "Beacon, Special
+ * mark"); "Navigation aid" for code 0 and for a code outside 0 to 31.
+ * @param {string|number|null|undefined} code
+ * @returns {string}
+ */
+export function aidToNavigationTypeName(code) {
+  const text = String(code ?? '').trim();
+  const index = /^\d+$/.test(text) ? Number(text) : -1;
+  return AID_TYPE_NAMES[index] ?? AID_TYPE_NAMES[0];
+}
+
+/**
+ * Words a vessel type uses for an aid to navigation. A vessel that works on
+ * one ("Buoy Tender", "Buoy-Laying Vessel") is a ship underway, not a mark on
+ * the water.
+ */
+const AID_TYPE_TEXT =
+  /navaid|\baton\b|aids? to nav|nav(igation)? aid|racon|lighthouse|lightship|light vessel|reference point|hand mark|cardinal|safe water|preferred channel|isolated danger|special mark|beacon|buoy/i;
+const AID_WORKER_TEXT = /tender|laying/i;
+
+/** ITU MID 99: the MMSI of an AIS aid-to-navigation station (99MIDxxxx). */
+const AID_MMSI = /^99\d{7}$/;
+
+/**
+ * Whether a vessel record is an aid to navigation (a buoy, beacon, mark,
+ * RACON or light) rather than a vessel: its type names one, or its MMSI is
+ * an aid-to-navigation station's. A numeric AIS ship type never names one.
+ * @param {{type?: string|number|null, mmsi?: string|number|null}} vessel
+ * @returns {boolean}
+ */
+export function isAidToNavigation({ type, mmsi } = {}) {
+  const text = String(type ?? '').trim();
+  if (AID_TYPE_TEXT.test(text) && !AID_WORKER_TEXT.test(text)) return true;
+  return AID_MMSI.test(String(mmsi ?? '').trim());
+}

src/data/vesselTypes.test.mjs

@@ -0,0 +1,47 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { aidToNavigationTypeName, isAidToNavigation } from './vesselTypes.js';
+
+test('an aid-to-navigation type code names its kind of aid', () => {
+  assert.equal(aidToNavigationTypeName(20), 'Cardinal Mark N');
+  assert.equal(aidToNavigationTypeName('13'), 'Beacon, Port hand');
+  assert.equal(aidToNavigationTypeName(2), 'RACON');
+  assert.equal(aidToNavigationTypeName(29), 'Safe Water');
+  assert.equal(aidToNavigationTypeName(31), 'Light Vessel / LANBY / Rigs');
+  // Code 0, a code past 31 and no code name no kind.
+  for (const code of [0, 32, -1, '', null, undefined, 'x'])
+    assert.equal(aidToNavigationTypeName(code), 'Navigation aid', code);
+});
+
+test('aids to navigation are known by their type, else their MMSI', () => {
+  for (const type of [
+    'Beacon, Special Mark',
+    'Cardinal Mark N',
+    'Port Hand Mark',
+    'Starboard Hand Mark',
+    'Safe Water',
+    'Isolated danger',
+    'Preferred Channel Port hand',
+    'RACON',
+    'Light Vessel / LANBY / Rigs',
+    'Reference point',
+    'Navigation aid',
+    'AtoN',
+    'Lighthouse',
+    'Buoy',
+  ])
+    assert.equal(isAidToNavigation({ type, mmsi: '' }), true, type);
+  // AIS aid-to-navigation stations are numbered 99MIDxxxx.
+  assert.equal(isAidToNavigation({ type: '', mmsi: '993672001' }), true);
+  assert.equal(isAidToNavigation({ type: '0', mmsi: ' 992351234 ' }), true);
+  for (const vessel of [
+    { type: 'Buoy Tender', mmsi: '366999001' },
+    { type: 'Buoy-Laying Vessel', mmsi: '' },
+    { type: '70', mmsi: '366999002' },
+    { type: '0', mmsi: '' },
+    { type: 'Cargo', mmsi: '99' },
+    { type: 'Passenger', mmsi: '9936720011' },
+    {},
+  ])
+    assert.equal(isAidToNavigation(vessel), false, JSON.stringify(vessel));
+});

src/layers/vessels/ownership.test.mjs

@@ -515,3 +515,27 @@ test('AIS feed rows stay keyed by their MMSI', async () => {
     ['235000001', '235000001'],
   );
 });
+
+test('an aid to navigation is drawn as a disc, a vessel as its chevron', async () => {
+  const aid = {
+    ...observation('993672001'),
+    mmsi: '993672001',
+    type: 'Port Hand Mark',
+    speedMps: 0,
+  };
+  const ship = { ...observation('366999002'), type: 'Cargo' };
+  const { layer, primitives } = setup({
+    async getSnapshot() {
+      return snapshot([aid, ship]);
+    },
+  });
+  await layer.update();
+  const svgOf = (id) => {
+    const primitive = [...primitives].find((p) => p.id?.id === id);
+    assert.ok(primitive, id);
+    return atob(primitive.image.split(',')[1]);
+  };
+  assert.match(svgOf('993672001'), /<circle/);
+  assert.doesNotMatch(svgOf('993672001'), /<path/);
+  assert.match(svgOf('366999002'), /<path/);
+});

src/layers/vessels/rendering.js

@@ -28,6 +28,10 @@ import {
   vesselModelSpec,
 } from '../../data/fleetModels.js';
 import { createFleetModelLayer } from '../../data/fleetModelInstances.js';
+import { isAidToNavigation } from '../../data/vesselTypes.js';
+
+/** An aid to navigation's disc: a bone white apart from every ship type's colour. */
+const AID_ICON_CSS = '#d9d2c0';
 
 /** How often vessels move on as the world clock plays (wall ms). */
 const FOLLOW_POSITION_MS = 250;
@@ -182,12 +186,14 @@ export function createRendering({
    * Best available real-world direction of travel for a vessel, degrees
    * clockwise from north (true heading preferred, course-over-ground fallback).
    * Screen rotation is computed from this by the shared projected-rotation
-   * pass in updateVisibility — never directly from the compass value.
+   * pass in updateVisibility — never directly from the compass value. An aid
+   * to navigation is fixed, so it has none.
    * @param {Object} record - Vessel record.
    * @returns {number} Course in degrees (0 when unknown).
    */
 
   function vesselCourseDeg(record) {
+    if (isAidToNavigation(record)) return 0;
     const direction = record.heading ?? record.course;
     return Number.isFinite(direction) ? direction : 0;
   }
@@ -195,6 +201,7 @@ export function createRendering({
   /**
    * Build (and cache) a chevron/delta-wing SVG data URL tinted for the vessel.
    * The shape points north (up) so billboard rotation maps directly to heading.
+   * An aid to navigation, which has no heading, is a ringed disc instead.
    * One icon is generated per color+variant and reused across all billboards.
    * @param {Object} record - Vessel record (drives per-type tint).
    * @param {boolean} selected - True for the white/brighter selected variant.
@@ -202,16 +209,25 @@ export function createRendering({
    */
 
   function shipIcon(record, selected) {
-    const cssColor = selected ? '#ffffff' : vesselTypeCss(record.type);
-    const key = `${cssColor}:${selected ? 'selected' : 'normal'}`;
+    const aid = isAidToNavigation(record);
+    const cssColor = selected
+      ? '#ffffff'
+      : aid
+        ? AID_ICON_CSS
+        : vesselTypeCss(record.type);
+    const key = `${cssColor}:${selected ? 'selected' : 'normal'}:${aid ? 'aid' : 'ship'}`;
     if (vesselState.shipIconCache.has(key))
       return vesselState.shipIconCache.get(key);
 
     const stroke = selected ? 'rgba(6,26,32,0.95)' : 'rgba(4,18,24,0.9)';
     const strokeWidth = selected ? 1.1 : 0.7;
+    const shape = aid
+      ? `<circle r="8" fill="${cssColor}" stroke="${stroke}" stroke-width="${strokeWidth * 2}"/>
+      <circle r="3" fill="${stroke}"/>`
+      : `<path d="M0,-14 L11,10 L4,7 L0,14 L-4,7 L-11,10 Z" fill="${cssColor}" stroke="${stroke}" stroke-width="${strokeWidth}" stroke-linejoin="round"/>`;
     const svg = `<svg xmlns="http://www.w3.org/2000/svg" width="32" height="32" viewBox="0 0 32 32">
     <g transform="translate(16,16)">
-      <path d="M0,-14 L11,10 L4,7 L0,14 L-4,7 L-11,10 Z" fill="${cssColor}" stroke="${stroke}" stroke-width="${strokeWidth}" stroke-linejoin="round"/>
+      ${shape}
     </g>
   </svg>`;
     const icon = 'data:image/svg+xml;base64,' + btoa(svg);
@@ -265,13 +281,14 @@ export function createRendering({
     let item = modelItems.get(record.id);
     if (!item || item.record !== record)
       item = { record, pickId: record, tint: null, modelOwnsVisual: false };
-    const specKey = `${record.type}|${record.length}|${record.beam}|${record.name}`;
+    const specKey = `${record.type}|${record.mmsi}|${record.length}|${record.beam}|${record.name}`;
     if (item.specKey !== specKey) {
       item.specKey = specKey;
       item.spec = vesselModelSpec(set, record);
     }
     item.position = getVisual(record).waterline;
-    item.headingDeg = vesselCourseDeg(record);
+    // An aid to navigation is a fixed mark: it does not turn to a heading.
+    item.headingDeg = item.spec?.fixed ? 0 : vesselCourseDeg(record);
     item.show = record.id !== state.cockpitSubjectId;
     return item;
   }