f16e6ddde1
- public/portfolio/ (FR + EN) : terminal Debian interactif (prompt dotriric@zektyc:~$, historique, commandes help/whoami/cat/neofetch/contact/sudo/exit/clear...) - Corrige un bug CSP-critique : String.prototype.link faisait traiter toutes les lignes texte comme des liens (A undefined) ; makeRich exige désormais typeof item.link === 'string' - Nav : lien Portfolio ajouté (components.js v=8, i18n nav.portfolio) - Sitemaps FR/EN : /fr/portfolio et /en/portfolio
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208 lines
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9.2 KiB
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<!doctype html>
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<head>
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<meta charset="utf-8" />
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<meta name="viewport" content="width=device-width, initial-scale=1" />
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<meta name="description" content="ZMap's per-road speed database: 90.5 million sampled points, 3.6 million km of roads mapped with their speed limit (OpenStreetMap), across all of Europe." />
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<meta name="robots" content="index, follow" />
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<title>Per-road speeds · ZMap · Zektyc</title>
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<link rel="alternate" hreflang="fr" href="https://riricdev.tail5ea5cd.ts.net/fr/zmap/vitesses-par-route/" />
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<meta property="og:title" content="Per-road speeds · ZMap" />
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<meta property="og:description" content="ZMap knows the speed limit of every road in Europe: 90.5 million points, 3.6 million km, built from OpenStreetMap data." />
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<link rel="icon" type="image/svg+xml" href="/favicon.svg" />
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<link rel="shortcut icon" href="/favicon.ico" />
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<link rel="stylesheet" href="/css/style.css?v=8" />
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<style>
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.stats-grid {
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display: grid;
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grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
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gap: 12px;
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font-size: 1.7em;
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line-height: 1.2;
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.stat span {
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font-size: 0.85em;
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opacity: 0.7;
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table.speeds {
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width: 100%;
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margin: 16px 0;
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}
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table.speeds th,
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table.speeds td {
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text-align: right;
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padding: 6px 10px;
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}
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table.speeds th:first-child,
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table.speeds td:first-child {
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text-align: left;
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border-radius: 4px;
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font-size: 0.9em;
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}
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</style>
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</head>
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<body>
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<header id="h"></header>
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<main class="legal" id="main">
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<p class="legal-note"><a href="/zmap/en/">← Back to ZMap</a></p>
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<h1>Per-road speeds</h1>
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<p class="legal-meta">
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ZMap's internal database · how it is built and what it contains
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</p>
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<div class="dev-banner">
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🧭 <strong>Navigation feature.</strong> ZMap snaps every point of your
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route to its actual road and reads its speed limit from a local database
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covering all of Europe — then keeps it cached on your phone for offline
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driving.
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</div>
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<section class="projects-page">
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<article class="card">
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<h3>The idea</h3>
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<p>
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Most navigation apps need a connection to know the speed limit. ZMap
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does it differently: a per-road speed-limit database is built from
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OpenStreetMap data and lives on the server. When a route is computed,
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each trip point is snapped to the nearest road and given its speed.
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The full route — speeds included — is then cached on the phone: while
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driving, no network request is needed.
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</p>
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</article>
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</section>
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<div class="stats-grid">
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<div class="stat"><b>90.5M</b><span>sampled points</span></div>
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<div class="stat"><b>3.6M km</b><span>of roads with a known speed</span></div>
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<div class="stat"><b>5,104</b><span>cells of 0.5° × 0.5°</span></div>
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<div class="stat"><b>370 MB</b><span>compressed grid (gzip)</span></div>
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<div class="stat"><b>40 m</b><span>sampling step along roads</span></div>
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<div class="stat"><b>5 B</b><span>per point (lon, lat, speed)</span></div>
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</div>
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<section class="projects-page">
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<article class="card">
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<h3>How it is built</h3>
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<ol>
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<li>
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<strong>Source:</strong> the OpenStreetMap Europe extract
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(Geofabrik, 34.8 GB) contains 98.2 million roads
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(<code>highway</code>).
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</li>
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<li>
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<strong>Filtering:</strong> <code>osmium tags-filter</code> keeps
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only the roads (8.5 GB), then only those carrying a speed
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(<code>maxspeed</code>) are kept — about 13 million.
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</li>
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<li>
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<strong>Sampling:</strong> a point is placed every 40 metres along
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each road, with its speed in km/h.
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</li>
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<li>
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<strong>Indexing:</strong> Europe is split into 0.5° cells
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(≈ 55 km), each subdivided into 32 × 32. Every point is quantized
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to ≈ 0.76 m and stored in 5 bytes, then the cell is gzip-compressed:
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90.5 million points in 370 MB total.
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</li>
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</ol>
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<p>
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It is fully reproducible: the build script
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(<code>build_maxspeed.py</code>) runs end to end on a small server.
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</p>
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</article>
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<article class="card">
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<h3>What is inside</h3>
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<p>
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Share of points by speed limit (most common values) :
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</p>
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<table class="speeds">
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<tr><th>Limit</th><th>Share</th><th></th></tr>
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<tr><td>50 km/h</td><td>26.2%</td><td><span class="bar" style="width:100%"></span></td></tr>
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<tr><td>30 km/h (30 zones)</td><td>18.5%</td><td><span class="bar" style="width:71%"></span></td></tr>
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<tr><td>90 km/h</td><td>9.5%</td><td><span class="bar" style="width:36%"></span></td></tr>
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<tr><td>80 km/h</td><td>9.2%</td><td><span class="bar" style="width:35%"></span></td></tr>
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<tr><td>70 km/h</td><td>6.0%</td><td><span class="bar" style="width:23%"></span></td></tr>
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<tr><td>60 km/h</td><td>5.7%</td><td><span class="bar" style="width:22%"></span></td></tr>
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<tr><td>100 km/h</td><td>4.6%</td><td><span class="bar" style="width:18%"></span></td></tr>
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<tr><td>40 km/h</td><td>3.3%</td><td><span class="bar" style="width:13%"></span></td></tr>
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<tr><td>48 km/h (30 mph, UK)</td><td>2.8%</td><td><span class="bar" style="width:11%"></span></td></tr>
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<tr><td>97 km/h (60 mph, UK)</td><td>2.4%</td><td><span class="bar" style="width:9%"></span></td></tr>
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<tr><td>32 km/h (20 mph, UK)</td><td>2.1%</td><td><span class="bar" style="width:8%"></span></td></tr>
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<tr><td>20 km/h (pedestrian zones)</td><td>2.1%</td><td><span class="bar" style="width:8%"></span></td></tr>
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<tr><td>120 km/h</td><td>1.8%</td><td><span class="bar" style="width:7%"></span></td></tr>
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<tr><td>130 km/h (motorways)</td><td>1.7%</td><td><span class="bar" style="width:6%"></span></td></tr>
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<tr><td>110 km/h</td><td>1.4%</td><td><span class="bar" style="width:5%"></span></td></tr>
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</table>
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<p class="legal-note">
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<em>Numeric</em> values found in OpenStreetMap. Actual limits may
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differ (roadworks, temporary signs, weather). Roads with no limit
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(e.g. some German sections) have no <code>maxspeed</code>: ZMap then
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shows no speed.
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</p>
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</article>
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<article class="card">
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<h3>In the app</h3>
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<p>
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The server returns, with every route, an array of speeds aligned with
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the geometry points (one value per point). The phone stores
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everything in its local cache: while driving, the current section's
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limit is read without network, and offline mode keeps the whole trip.
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Snapping a 4,500-point route takes about 170 ms on the server.
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</p>
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</article>
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<article class="card">
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<h3>Accuracy and coverage</h3>
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<ul>
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<li>Coverage: all of Europe, longitude −12° to 46°, latitude 27° to 72°.</li>
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<li>Snapping: the nearest road within 40 m of the point.</li>
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<li>Point location accuracy: ≈ 0.76 m.</li>
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<li>Data: OpenStreetMap, free (ODbL licence).</li>
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</ul>
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</article>
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</section>
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</main>
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<footer id="f"></footer>
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<script src="/js/theme.js" defer></script>
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<script src="/js/global.js?v=1" defer></script>
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