fix: DriftSimulationService v2 — ST_Translate au lieu de sample+ConcaveHull
L'ancienne approche (ST_GeneratePoints × 40 + ST_ConcaveHull) avait un défaut majeur : les points aléatoires pouvaient ne pas couvrir les patches locaux (ex: le patch à 3.61km de Barbados), donnant des distances absurdes à H+6 (654km). Nouvelle approche : - ST_Translate(geometry, dx_deg, dy_deg) : translation directe du MULTIPOLYGON source → chaque patch individuel se déplace correctement - ST_Buffer(... DIFFUSION_M × √horizon) : diffusion turbulente via dilatation (H+6 ≈ +3.7km, H+48 ≈ +10.4km) — formes qui s'élargissent sans perdre la structure - Déterministe : pas d'aléatoire, distances ST_Distance fiables Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Gwadaking
@@ -12,27 +12,29 @@ use Psr\Log\LoggerInterface;
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/**
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* Simule la dérive des sargasses à partir d'une observation.
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*
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* Algorithme :
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* 1. Échantillonnage PostGIS (ST_GeneratePoints) → N points internes
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* 2. Pour chaque point, déplacement horaire via vecteur vent Open-Meteo
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* (modèle Stokes : 3% vitesse vent = contribution sargassum)
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* 3. Reconstruction du polygone par ST_ConcaveHull des points déplacés
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* Algorithme v2 (ST_Translate) :
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* 1. Cumul du vecteur de dérive heure par heure (vent Open-Meteo × facteur Stokes 3%)
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* 2. Translation directe de la géométrie source via ST_Translate (PostGIS)
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* 3. Buffer croissant (√horizon) pour simuler la diffusion turbulente
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* 4. Sauvegarde d'un SargassumForecast par horizon (H+6/12/24/48)
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*
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* Avantages vs l'ancienne approche sample+ConcaveHull :
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* - Déterministe : pas d'aléatoire sur le polygone, distances cohérentes
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* - Conserve la structure MULTIPOLYGON : chaque patch reste localement correct
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* - ST_Distance donne la vraie distance au patch le plus proche (pas au centroïde)
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*/
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class DriftSimulationService
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{
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private const HORIZONS = [6, 12, 24, 48];
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private const SAMPLE_POINTS = 40;
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private const WIND_FACTOR = 0.03; // 3% du vent = dérive Stokes
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private const MODEL_VERSION = '1.1.0';
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private const CONCAVITY = 0.7; // paramètre ST_ConcaveHull (0=convex, 1=très concave)
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private const DIFFUSION_M = 600; // m/heure — diffusion turbulente horizontale (marche aléatoire)
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private const HORIZONS = [6, 12, 24, 48];
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private const WIND_FACTOR = 0.03; // 3% vitesse vent = dérive de Stokes sargassum
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private const DIFFUSION_M = 1500; // m — coefficient de diffusion (rayon du buffer à 1h)
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private const MODEL_VERSION = '2.0.0';
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public function __construct(
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private OpenMeteoClient $weather,
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private Connection $connection,
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private OpenMeteoClient $weather,
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private Connection $connection,
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private EntityManagerInterface $em,
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private LoggerInterface $logger,
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private LoggerInterface $logger,
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) {}
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/**
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@@ -44,41 +46,44 @@ class DriftSimulationService
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{
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$id = (string) $observation->getId();
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// Centroïde de l'observation → point de référence pour Open-Meteo
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$centroid = $this->getCentroid($id);
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if ($centroid === null) {
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$this->logger->warning('Centroid unavailable, skipping forecast', ['id' => $id]);
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return [];
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}
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// Vents horaires sur 3 jours (72h)
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$windData = $this->weather->getHourlyWind($centroid['lat'], $centroid['lng']);
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// Points échantillonnés à l'intérieur du polygone
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$samplePoints = $this->samplePoints($id);
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if (empty($samplePoints)) {
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$this->logger->warning('No sample points, skipping forecast', ['id' => $id]);
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return [];
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}
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$forecasts = [];
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$currentPoints = $samplePoints; // état courant des points
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$prevHorizon = 0;
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$forecasts = [];
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$totalDxM = 0.0;
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$totalDyM = 0.0;
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$prevHorizon = 0;
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foreach (self::HORIZONS as $horizon) {
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// Déplace les points heure par heure de $prevHorizon à $horizon
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$currentPoints = $this->displacePoints($currentPoints, $windData, $prevHorizon, $horizon);
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// Cumul du déplacement en mètres de $prevHorizon à $horizon
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for ($h = $prevHorizon; $h < $horizon; $h++) {
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$wind = $windData[$h] ?? ['speed' => 0, 'direction' => 0];
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$speed = $wind['speed'] * self::WIND_FACTOR; // m/s
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$dirRad = deg2rad($wind['direction']);
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$totalDxM += $speed * sin($dirRad) * 3600; // m/h Est-Ouest
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$totalDyM += $speed * cos($dirRad) * 3600; // m/h Nord-Sud
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}
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// Reconstruit le polygone depuis les points déplacés
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$geometry = $this->reconstructPolygon($currentPoints);
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// Conversion m → degrés (au centroïde de l'observation)
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$dxDeg = $totalDxM / (111320.0 * cos(deg2rad($centroid['lat'])));
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$dyDeg = $totalDyM / 111320.0;
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// Buffer de diffusion : croît comme √horizon (diffusion Brownienne)
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$bufferM = self::DIFFUSION_M * sqrt($horizon);
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$geometry = $this->buildForecastGeometry($id, $dxDeg, $dyDeg, $bufferM);
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if ($geometry === null) {
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$this->logger->info("No polygon for H+{$horizon}", ['id' => $id]);
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$prevHorizon = $horizon;
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continue;
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}
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// Vecteur de dérive moyen sur cette période
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$driftVector = $this->avgDriftVector($windData, $prevHorizon, $horizon);
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$driftVector = $this->avgDriftVector($windData, 0, $horizon);
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$forecast = new SargassumForecast();
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$forecast->setSourceObservation($observation);
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@@ -117,109 +122,52 @@ class DriftSimulationService
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}
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/**
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* Génère N points aléatoires à l'intérieur du polygone via PostGIS.
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* Traduit la géométrie source de $dxDeg/$dyDeg degrés, puis dilate de $bufferM mètres.
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*
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* @return array<int, array{lat: float, lng: float}>
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* ST_Translate conserve la structure MULTIPOLYGON : chaque patch individuel
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* se déplace de façon identique → ST_Distance retourne la vraie distance
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* au patch le plus proche, pas au centroïde global.
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*/
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private function samplePoints(string $observationId): array
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{
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$rows = $this->connection->fetchAllAssociative(
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'SELECT ST_X(geom) AS lng, ST_Y(geom) AS lat
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FROM (
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SELECT (ST_Dump(ST_GeneratePoints(geometry, :n))).geom
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FROM sargassum_observation WHERE id = :id
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) AS pts',
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['n' => self::SAMPLE_POINTS, 'id' => $observationId]
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);
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return array_map(fn($r) => ['lat' => (float) $r['lat'], 'lng' => (float) $r['lng']], $rows);
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}
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/**
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* Déplace un ensemble de points sur la période [$fromHour..$toHour]
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* en appliquant le vecteur vent heure par heure.
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*
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* @param array<int, array{lat: float, lng: float}> $points
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* @param array<int, array{speed: float, direction: float}> $windData
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* @return array<int, array{lat: float, lng: float}>
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*/
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private function displacePoints(array $points, array $windData, int $fromHour, int $toHour): array
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{
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for ($h = $fromHour; $h < $toHour; $h++) {
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$wind = $windData[$h] ?? ['speed' => 0, 'direction' => 0];
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$speed = $wind['speed'] * self::WIND_FACTOR; // m/s
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$dirRad = deg2rad($wind['direction']);
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// Déplacement en mètres sur 1 heure
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$dx = $speed * sin($dirRad) * 3600; // Est-Ouest (m)
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$dy = $speed * cos($dirRad) * 3600; // Nord-Sud (m)
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foreach ($points as &$pt) {
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// Advection : conversion m → degrés
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$pt['lat'] += $dy / 111320;
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$pt['lng'] += $dx / (111320 * cos(deg2rad($pt['lat'])));
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// Diffusion turbulente : marche aléatoire indépendante par point
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// Simule la dispersion naturelle du patch sous l'effet des courants de méso-échelle
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$perturbLat = (mt_rand(-1000, 1000) / 1000.0) * self::DIFFUSION_M / 111320;
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$perturbLng = (mt_rand(-1000, 1000) / 1000.0) * self::DIFFUSION_M / (111320 * cos(deg2rad($pt['lat'])));
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$pt['lat'] += $perturbLat;
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$pt['lng'] += $perturbLng;
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}
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unset($pt);
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}
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return $points;
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}
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/**
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* Reconstruit un MULTIPOLYGON depuis un nuage de points via PostGIS.
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*/
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/** @param array<int, array{lat: float, lng: float}> $points */
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private function reconstructPolygon(array $points): ?string
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{
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if (count($points) < 3) {
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return null;
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}
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$wktPoints = implode(',', array_map(
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fn($p) => sprintf('%f %f', $p['lng'], $p['lat']),
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$points
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));
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private function buildForecastGeometry(
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string $observationId,
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float $dxDeg,
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float $dyDeg,
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float $bufferM,
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): ?string {
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$row = $this->connection->fetchAssociative(
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"SELECT ST_AsText(
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'SELECT ST_AsText(
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ST_Multi(
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ST_ConcaveHull(
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ST_GeomFromText('MULTIPOINT({$wktPoints})', 4326),
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:concavity
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)
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ST_Buffer(
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ST_Translate(geometry, :dx, :dy)::geography,
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:buffer
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)::geometry
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)
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) AS wkt",
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['concavity' => self::CONCAVITY]
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) AS wkt
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FROM sargassum_observation WHERE id = :id',
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['id' => $observationId, 'dx' => $dxDeg, 'dy' => $dyDeg, 'buffer' => $bufferM]
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);
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return ($row !== false && $row['wkt']) ? 'SRID=4326;' . $row['wkt'] : null;
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return ($row !== false && isset($row['wkt']) && $row['wkt'] !== null)
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? 'SRID=4326;' . $row['wkt']
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: null;
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}
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/**
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* Calcule le vecteur de dérive moyen (composantes lat/lng) sur une période.
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*/
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/**
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* Vecteur de dérive moyen (composantes lat/lng en m/s) sur [fromHour..toHour].
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*
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* @param array<int, array{speed: float, direction: float}> $windData
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* @return array{lat: float, lng: float}
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*/
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private function avgDriftVector(array $windData, int $fromHour, int $toHour): array
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{
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$count = $toHour - $fromHour;
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$count = $toHour - $fromHour;
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$sumLat = 0.0;
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$sumLng = 0.0;
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for ($h = $fromHour; $h < $toHour; $h++) {
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$wind = $windData[$h] ?? ['speed' => 0, 'direction' => 0];
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$speed = $wind['speed'] * self::WIND_FACTOR;
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$dirRad = deg2rad($wind['direction']);
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$wind = $windData[$h] ?? ['speed' => 0, 'direction' => 0];
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$speed = $wind['speed'] * self::WIND_FACTOR;
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$dirRad = deg2rad($wind['direction']);
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$sumLat += $speed * cos($dirRad);
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$sumLng += $speed * sin($dirRad);
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}
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