Araya's Project
110 lines
2.8 KiB
PHP
110 lines
2.8 KiB
PHP
<?php
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/**
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* Helper geometri & respons JSON.
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*
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* Perhitungan dilakukan di sisi server agar otoritatif:
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* - Panjang LineString -> haversine (meter)
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* - Luas / keliling Polygon -> rumus area geodesik bola (meter & m2)
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*
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* Koordinat mengikuti format GeoJSON: [longitude, latitude].
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*/
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const EARTH_RADIUS = 6378137.0; // radius WGS84 (meter)
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/** Kirim respons JSON lalu hentikan eksekusi. */
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function json_response($data, int $status = 200): void
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{
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http_response_code($status);
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header('Content-Type: application/json; charset=utf-8');
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echo json_encode($data, JSON_UNESCAPED_UNICODE);
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exit;
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}
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/** Ambil & decode body JSON dari request. */
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function read_json_body(): array
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{
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$raw = file_get_contents('php://input');
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$data = json_decode($raw, true);
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return is_array($data) ? $data : [];
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}
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/** Jarak haversine antar dua titik [lng, lat] dalam meter. */
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function haversine(array $a, array $b): float
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{
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$lon1 = deg2rad($a[0]);
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$lat1 = deg2rad($a[1]);
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$lon2 = deg2rad($b[0]);
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$lat2 = deg2rad($b[1]);
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$dLat = $lat2 - $lat1;
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$dLon = $lon2 - $lon1;
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$h = sin($dLat / 2) ** 2
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+ cos($lat1) * cos($lat2) * sin($dLon / 2) ** 2;
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return 2 * EARTH_RADIUS * asin(min(1.0, sqrt($h)));
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}
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/**
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* Panjang total sebuah LineString (array of [lng, lat]) dalam meter.
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*/
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function line_length(array $coords): float
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{
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$total = 0.0;
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$n = count($coords);
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for ($i = 1; $i < $n; $i++) {
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$total += haversine($coords[$i - 1], $coords[$i]);
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}
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return $total;
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}
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/**
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* Luas polygon geodesik (ring tunggal, array of [lng, lat]) dalam meter persegi.
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* Memakai pendekatan integral bola (mirip Google Maps computeSignedArea).
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*/
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function ring_area(array $ring): float
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{
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$n = count($ring);
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if ($n < 3) {
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return 0.0;
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}
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$area = 0.0;
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for ($i = 0; $i < $n; $i++) {
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$p1 = $ring[$i];
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$p2 = $ring[($i + 1) % $n];
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$area += deg2rad($p2[0] - $p1[0])
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* (2 + sin(deg2rad($p1[1])) + sin(deg2rad($p2[1])));
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}
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$area = $area * EARTH_RADIUS * EARTH_RADIUS / 2.0;
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return abs($area);
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}
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/** Keliling polygon (ring tunggal) dalam meter. */
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function ring_perimeter(array $ring): float
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{
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if (count($ring) < 2) {
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return 0.0;
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}
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// Pastikan ring tertutup untuk perhitungan keliling.
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$closed = $ring;
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if ($closed[0] !== $closed[count($closed) - 1]) {
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$closed[] = $closed[0];
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}
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return line_length($closed);
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}
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/**
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* Validasi & ekstrak geometry GeoJSON.
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* Mengembalikan [type, coordinates] atau null bila tidak valid.
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*/
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function parse_geometry($geojson): ?array
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{
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if (is_string($geojson)) {
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$geojson = json_decode($geojson, true);
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}
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if (!is_array($geojson) || empty($geojson['type']) || !isset($geojson['coordinates'])) {
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return null;
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}
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return [$geojson['type'], $geojson['coordinates']];
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}
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