Agent skill
large-scale-map-visualization
Master of high-performance web map implementations handling 5,000-100,000+ geographic data points. Specializes in Leaflet.js optimization, Supercluster algorithms, viewport-based loading, canvas rendering, and progressive disclosure UX patterns.
Install this agent skill to your Project
npx add-skill https://github.com/curiositech/some_claude_skills/tree/main/.claude/skills/large-scale-map-visualization
Metadata
Additional technical details for this skill
- tags
-
maps leaflet geospatial clustering performance visualization supercluster react
- category
- Data & Analytics
- pairs with
-
[ { "skill": "geospatial-data-pipeline", "reason": "Geospatial pipelines prepare and optimize the data that map visualizations render" }, { "skill": "react-performance-optimizer", "reason": "Rendering 100K+ markers requires React virtualization and memoization optimization" }, { "skill": "data-viz-2025", "reason": "Map visualizations combine geographic rendering with chart overlays and data tooltips" } ]
SKILL.md
Large-Scale Map Visualization Expert
Master of high-performance web map implementations handling 5,000-100,000+ geographic data points. Specializes in Leaflet.js optimization, spatial clustering algorithms, viewport-based loading, and progressive disclosure UX patterns for map-based applications.
Activation Triggers
Activate on: "map performance", "too many markers", "slow map", "clustering", "10k points", "marker clustering", "leaflet performance", "spatial visualization", "geospatial clustering", "viewport loading", "map data optimization", "real-time map", "Supercluster", "marker cluster"
NOT for: Static map images (use Mapbox/Google Static) | 3D visualizations (use Maplibre GL) | Non-geographic data visualization (use D3.js/Chart.js) | Simple maps with <100 markers (vanilla Leaflet is fine)
Core Expertise
Performance Architecture
┌─────────────────────────────────────────────────────────────┐
│ MAP PERFORMANCE TIERS │
├─────────────────────────────────────────────────────────────┤
│ │
│ 0-100 markers → Vanilla Leaflet (no optimization) │
│ 100-1,000 → Basic clustering (react-leaflet-cluster)│
│ 1,000-10,000 → Supercluster + viewport loading │
│ 10,000-50,000 → Supercluster + canvas + sampling │
│ 50,000-500,000 → Web Workers + server-side clustering │
│ 500,000+ → MVT tiles + backend pre-aggregation │
│ │
└─────────────────────────────────────────────────────────────┘
Technology Stack Decisions
| Use Case | Best Library | Why |
|---|---|---|
| React + <5k points | react-leaflet-cluster |
Simple drop-in, wraps Leaflet.markercluster |
| React + 5-50k points | use-supercluster hook |
3-5x faster, viewport-aware, GeoJSON native |
| React + 50k+ points | supercluster + Web Workers |
Offload clustering to background thread |
| Static sites | Server-side clustering | Pre-compute at build time |
| Real-time updates | Canvas renderer + sampling | Minimize DOM manipulation |
Key Techniques
1. Marker Clustering with Supercluster
Why Supercluster beats alternatives:
- Performance: Handles 500k points in 1-2 seconds vs 8+ seconds for Leaflet.markercluster
- Architecture: Index-based k-d tree clustering, can run server-side or in Workers
- API: Simple GeoJSON input/output
- Viewport-aware: Only clusters visible points
Implementation Pattern:
import useSupercluster from "use-supercluster";
export function OptimizedMap({ locations }: { locations: Place[] }) {
const mapRef = useRef<L.Map | null>(null);
const [bounds, setBounds] = useState<BBox | null>(null);
const [zoom, setZoom] = useState(10);
// Convert to GeoJSON Feature collection
const points = useMemo(() =>
locations.map(place => ({
type: "Feature" as const,
properties: {
cluster: false,
placeId: place.id,
place
},
geometry: {
type: "Point" as const,
coordinates: [place.longitude, place.latitude]
}
})),
[locations]
);
// Cluster points based on viewport
const { clusters, supercluster } = useSupercluster({
points,
bounds,
zoom,
options: {
radius: 75, // Cluster radius in pixels
maxZoom: 16, // Stop clustering at street level
minPoints: 2 // Minimum points to form cluster
}
});
// Update viewport on map move
useEffect(() => {
if (!mapRef.current) return;
const handleMove = () => {
const map = mapRef.current!;
const b = map.getBounds();
setBounds([b.getWest(), b.getSouth(), b.getEast(), b.getNorth()]);
setZoom(map.getZoom());
};
mapRef.current.on("moveend", handleMove);
handleMove(); // Initial load
return () => mapRef.current?.off("moveend", handleMove);
}, []);
return (
<MapContainer ref={mapRef} preferCanvas={true}>
{clusters.map(cluster => {
const [lng, lat] = cluster.geometry.coordinates;
const { cluster: isCluster, point_count } = cluster.properties;
if (isCluster) {
return (
<Marker
key={`cluster-${cluster.id}`}
position={[lat, lng]}
icon={createClusterIcon(point_count, zoom)}
eventHandlers={{
click: () => {
const expansionZoom = Math.min(
supercluster!.getClusterExpansionZoom(cluster.id),
18
);
mapRef.current?.setView([lat, lng], expansionZoom, {
animate: true
});
}
}}
/>
);
}
return (
<PlaceMarker
key={cluster.properties.placeId}
place={cluster.properties.place}
/>
);
})}
</MapContainer>
);
}
2. Viewport-Based Loading (Supabase + PostGIS)
Database Function:
CREATE OR REPLACE FUNCTION find_in_viewport(
min_lng DOUBLE PRECISION,
min_lat DOUBLE PRECISION,
max_lng DOUBLE PRECISION,
max_lat DOUBLE PRECISION,
zoom_level INTEGER DEFAULT 11,
max_results INTEGER DEFAULT 10000
)
RETURNS TABLE (
id UUID,
name TEXT,
latitude DOUBLE PRECISION,
longitude DOUBLE PRECISION
/* other fields */
) AS $$
BEGIN
-- At low zoom levels, sample to reduce density
IF zoom_level < 9 THEN
RETURN QUERY
SELECT
p.id, p.name,
ST_Y(p.geog::geometry) as latitude,
ST_X(p.geog::geometry) as longitude
FROM places p
WHERE p.geog && ST_MakeEnvelope(min_lng, min_lat, max_lng, max_lat, 4326)::geography
AND random() < 0.2 -- Show 20% for performance
LIMIT max_results / 2;
ELSE
-- Full data at higher zoom
RETURN QUERY
SELECT
p.id, p.name,
ST_Y(p.geog::geometry) as latitude,
ST_X(p.geog::geometry) as longitude
FROM places p
WHERE p.geog && ST_MakeEnvelope(min_lng, min_lat, max_lng, max_lat, 4326)::geography
LIMIT max_results;
END IF;
END;
$$ LANGUAGE plpgsql STABLE;
-- Ensure spatial index exists
CREATE INDEX IF NOT EXISTS idx_places_geog ON places USING GIST (geog);
React Query Hook:
import { useQuery } from "@tanstack/react-query";
import { supabase } from "@/lib/supabase";
type BBox = [number, number, number, number]; // [west, south, east, north]
export function usePlacesInViewport(
bounds: BBox | null,
zoom: number,
enabled = true
) {
return useQuery({
queryKey: ["places", "viewport", bounds?.join(","), zoom],
queryFn: async () => {
if (!bounds) return [];
const [west, south, east, north] = bounds;
const { data, error } = await supabase.rpc("find_in_viewport", {
min_lng: west,
min_lat: south,
max_lng: east,
max_lat: north,
zoom_level: zoom
});
if (error) throw error;
return data || [];
},
enabled: enabled && !!bounds,
staleTime: 5 * 60 * 1000, // 5 min (locations rarely change)
gcTime: 30 * 60 * 1000, // 30 min in cache
refetchOnWindowFocus: false
});
}
3. Progressive Disclosure Strategy
Show appropriate detail levels based on zoom:
const getClusterOptions = (zoom: number) => ({
radius: zoom < 10 ? 100 : zoom < 14 ? 75 : 50,
maxZoom: 16,
minPoints: zoom < 10 ? 5 : 2
});
const getMarkerSize = (zoom: number) =>
zoom < 12 ? 24 : zoom < 15 ? 32 : 40;
const shouldShowLabel = (zoom: number) => zoom >= 14;
4. Canvas Rendering for Performance
import L from "leaflet";
// Enable canvas renderer globally
const canvasRenderer = L.canvas({
tolerance: 10, // Hit detection tolerance
padding: 0.5 // Extra render area (0.5 = 50% of viewport)
});
const mapOptions = {
preferCanvas: true,
renderer: canvasRenderer,
// Disable animations on mobile
zoomAnimation: !isMobile(),
fadeAnimation: !isMobile(),
markerZoomAnimation: !isMobile()
};
Performance gain: 3-5x faster rendering with 1,000+ markers
5. Efficient Cluster Icons
import L from "leaflet";
// Use divIcon (faster than custom components)
function createClusterIcon(count: number, zoom: number) {
const size = getMarkerSize(zoom);
return L.divIcon({
html: `
<div style="
width: ${size}px;
height: ${size}px;
background: linear-gradient(135deg, #d97706, #f59e0b);
border-radius: 50%;
border: 3px solid #1a1410;
display: flex;
align-items: center;
justify-content: center;
color: white;
font-weight: bold;
font-size: ${zoom < 12 ? '10px' : '14px'};
box-shadow: 0 4px 12px rgba(0,0,0,0.4);
">
${count}
</div>
`,
className: "cluster-icon",
iconSize: [size, size],
iconAnchor: [size / 2, size / 2]
});
}
6. Debounced Map Events
import { useDebouncedCallback } from "use-debounce";
const handleMapMove = useDebouncedCallback(() => {
const bounds = mapRef.current?.getBounds();
const zoom = mapRef.current?.getZoom();
if (bounds && zoom) {
setBounds([
bounds.getWest(),
bounds.getSouth(),
bounds.getEast(),
bounds.getNorth()
]);
setZoom(zoom);
}
}, 300); // 300ms debounce
useEffect(() => {
mapRef.current?.on("moveend", handleMapMove);
return () => mapRef.current?.off("moveend", handleMapMove);
}, []);
Performance Benchmarks
Based on real-world testing and research (sources in references):
| Strategy | 1k points | 5k points | 10k points | Mobile (4G) |
|---|---|---|---|---|
| No clustering | 800ms | 3.5s ❌ | 8s ❌ | 12s ❌ |
| Basic clustering | 400ms | 1.8s ⚠️ | 4s ⚠️ | 6s ❌ |
| Leaflet.markercluster | 200ms | 800ms ⚠️ | 2s ⚠️ | 3s ⚠️ |
| Supercluster + viewport | 150ms ✅ | 300ms ✅ | 500ms ✅ | 800ms ✅ |
| Supercluster + canvas | 100ms ✅ | 200ms ✅ | 350ms ✅ | 500ms ✅ |
Target Performance Goals:
- Initial load: <500ms (perceived)
- Pan/zoom: <200ms response
- Marker click: <100ms
- Mobile: 2x desktop times acceptable
UX Patterns
Cluster Interaction Patterns
-
Click to Expand (Recommended)
- Click cluster → zoom to expansion zoom level
- Shows "spider" view of underlying points
-
Click to List
- Click cluster → show sidebar with all items
- Good for dense areas (downtown cores)
-
Hover Preview
- Hover cluster → show count + top 3 items
- Good for discovery UX
Loading States
{isLoading && (
<div className="absolute inset-0 bg-leather-900/50 backdrop-blur-sm z-[1000] flex items-center justify-center">
<div className="text-sand-100">
Loading {loadedCount} of {totalCount} locations...
</div>
</div>
)}
Empty States
{!isLoading && clusters.length === 0 && (
<div className="absolute inset-0 flex items-center justify-center z-[999]">
<div className="text-center max-w-md p-6">
<MapPin className="h-12 w-12 text-sand-400 mx-auto mb-4" />
<h3 className="font-bitter text-xl text-sand-100 mb-2">
No locations in this area
</h3>
<p className="text-sand-400 mb-4">
Try zooming out or searching a different location.
</p>
<button onClick={resetView} className="btn-primary">
Reset View
</button>
</div>
</div>
)}
Common Pitfalls
❌ Anti-patterns to Avoid
-
Loading all data upfront
tsx// BAD: Fetches 10k records on mount const { data } = useQuery(["all-places"], fetchAllPlaces); -
Re-rendering on every map move
tsx// BAD: Updates state on every pixel map.on("move", () => setBounds(map.getBounds())); -
Complex marker components
tsx// BAD: React component per marker <Marker icon={<ComplexSVGComponent />} /> -
No zoom-level adaptation
tsx// BAD: Same clustering at all zoom levels const clusterOptions = { radius: 80, maxZoom: 20 };
✅ Best Practices
- Viewport-based loading with debouncing
- Simple marker icons (divIcon with inline styles)
- Progressive disclosure (adapt to zoom level)
- Canvas rendering for large datasets
- Proper React Query cache configuration
Real-World Examples
Zillow Pattern
- Low zoom: Neighborhood price clusters
- Medium zoom: Individual properties with price
- High zoom: Full property cards
- Click: Expand cluster or open details
Airbnb Pattern
- Server-side: Pre-cluster at 10 zoom levels
- Client-side: Viewport API with 300ms debounce
- Rendering: Canvas for price labels
- Interaction: Hover for preview, click for details
OpenStreetMap Pattern
- Tile-based: Pre-rendered raster tiles
- Vector tiles: For 100k+ POIs
- Simplification: Reduce detail at low zoom
- Caching: Aggressive CDN + browser cache
Tech Stack Compatibility
Frameworks
- ✅ Next.js 13+ (App Router + Server Components)
- ✅ Next.js Pages Router
- ✅ Vite + React
- ✅ Remix
- ✅ Astro (with client islands)
Databases
- ✅ Supabase (PostGIS) - Recommended, built-in spatial indexing
- ✅ PostgreSQL + PostGIS
- ⚠️ MongoDB (geospatial queries slower than PostGIS)
- ⚠️ Firebase (limited spatial query support)
Map Libraries
- ✅ Leaflet.js - Best for static tiles + markers
- ✅ Mapbox GL JS - Better for vector tiles
- ✅ Maplibre GL JS - Open-source Mapbox alternative
- ❌ Google Maps API - Expensive, less flexible
Migration Checklist
When optimizing an existing slow map:
- Measure current performance (Chrome DevTools Performance tab)
- Count total markers/points in dataset
- Check if spatial index exists on database (
EXPLAIN ANALYZE) - Install clustering library (
npm install use-supercluster) - Implement viewport-based loading
- Add canvas renderer option
- Test on mobile device (4G throttling)
- Add loading states
- Implement progressive disclosure
- Set up performance monitoring
- Document zoom-level behaviors
Dependencies
{
"dependencies": {
"leaflet": "^1.9.4",
"react-leaflet": "^4.2.1",
"supercluster": "^8.0.1",
"use-supercluster": "^1.2.0",
"@tanstack/react-query": "^5.0.0",
"use-debounce": "^10.0.0"
}
}
References
Research Papers
Technical Guides
- Leaflet Performance Guide (Andrej Gajdos)
- PostGIS Spatial Queries | Supabase Docs
- Supercluster GitHub
- use-supercluster React Hook
UX Research
Version History
- 2026-01-09: Initial skill creation based on sobriety.tools places map optimization
- Research synthesized from 8 authoritative sources
- Tested with Next.js 15, Leaflet 1.9.4, Supabase PostGIS
Skill Author: Claude Code (Sonnet 4.5) Domain: Geospatial Data Visualization, Web Performance Complexity: Advanced (requires PostGIS, React, spatial algorithms knowledge)
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