leaflet_svelte/DEBUGGING_WIND_LAYER.md

Wind Layer Debugging Guide

✅ Fixes Applied

1. Removed Leaflet Dependencies

• ❌ Deleted src/lib/ext/leaflet-ruler/leaflet-ruler.ts
• This file was causing import errors for missing 'leaflet' module

2. Fixed Type Definitions

File: src/lib/types.ts

Before:

export type LatLngTuple = [number, number];

After:

export type LatLngTuple = [number, number] | [number, number, number]; // Support 2D and 3D
export interface LatLngLiteral {
	lat: number;
	lng: number;
	alt?: number; // Optional altitude
}

Why: Prediction and telemetry data includes altitude (3D coordinates), so types need to support [lat, lng, alt] tuples.

3. Dev Server Status

✅ Server running successfully on http://localhost:5175/ ✅ No build errors in console ✅ Wind layer package installed: @sakitam-gis/maplibre-wind@2.0.3

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🔍 Debugging 500 Internal Server Error

If you're still seeing a 500 error, check these areas:

1. Check Browser Console

Open browser DevTools (F12) and look for:

// Expected success logs:
"WindVisualization mounted with MapLibre map"
"Wind data available: Array(2)"
"Wind data stats - U: [-21.32, 26.80], V: [-21.57, 21.42]"
"Wind layers initialized successfully"

// Error logs to watch for:
"Failed to process wind data"
"Error initializing wind layers:"
"Missing U or V wind components"

2. Check Network Tab

Look for failed requests:

• /src/routes/testVelo.json - Wind data file
• MapLibre GL CSS/JS assets
• Wind layer assets

3. Verify Wind Data File

# Check if file exists
ls -la src/routes/testVelo.json

# Check file size (should be ~76KB)
du -h src/routes/testVelo.json

# Verify JSON is valid
cat src/routes/testVelo.json | python -m json.tool > /dev/null && echo "Valid JSON" || echo "Invalid JSON"

4. Check Map Component

The Map component should pass both props:

<WindVisualization {map} {windData} />

Verify in src/lib/components/Map.svelte:

• Line ~155-157: WindVisualization component exists
• windData is loaded from fetch
• map instance is created

5. SSR (Server-Side Rendering) Issues

MapLibre and wind-layer are client-only. Ensure:

// In +page.ts or +page.server.ts
export const ssr = false;

Check: src/routes/predict/+page.ts

6. Build Issues

Try clearing cache and rebuilding:

# Clear SvelteKit cache
rm -rf .svelte-kit

# Clear node_modules (if needed)
rm -rf node_modules
npm install

# Restart dev server
npm run dev

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🧪 Test Cases

Test 1: Component Loads

1. Navigate to /predict
2. Open console (F12)
3. Look for "WindVisualization mounted" message
4. ✅ Success if no errors

Test 2: Wind Data Loaded

1. Check console for "Wind data available: Array(2)"
2. Verify data has U-component (parameterNumber: 2)
3. Verify data has V-component (parameterNumber: 3)
4. ✅ Success if both components present

Test 3: Layers Initialize

1. Look for "Wind layers initialized successfully"
2. Check map has particle animation visible
3. Toggle checkboxes work
4. ✅ Success if particles animate

Test 4: No Console Errors

1. Check for any red errors in console
2. Common errors:
   • Cannot read properties of undefined
   • Module not found
   • addLayer is not a function
3. ✅ Success if no errors

---

🐛 Common Errors & Solutions

Error: "Cannot find module '@sakitam-gis/maplibre-wind'"

Solution:

npm install @sakitam-gis/maplibre-wind --save

Error: "map.addLayer is not a function"

Cause: Map not fully initialized

Solution: Component already waits for map load:

if (map.loaded()) {
    initializeWindLayers();
} else {
    map.on('load', initializeWindLayers);
}

Error: "Missing U or V wind components"

Cause: Wind data file corrupted or wrong format

Solution: Verify testVelo.json has 2 objects with:

• First: header.parameterNumber: 2 (U-component)
• Second: header.parameterNumber: 3 (V-component)

Error: "Failed to process wind data"

Cause: Data structure doesn't match expected format

Solution: Check data has:

{
  header: { nx, ny, parameterNumber },
  data: [/* array of numbers */]
}

Error: Layer already exists

Cause: Trying to add layer that's already on map

Solution: Component checks before adding:

if (!map.getLayer('wind-particles')) {
    map.addLayer(particleLayer);
}

---

📊 Expected Console Output

Successful Load:

WindVisualization mounted with MapLibre map
Wind data available: Array(2) [{header: {…}, data: Array(65160)}, {header: {…}, data: Array(65160)}]
Wind data stats - U: [-21.32, 26.80], V: [-21.57, 21.42]
Processed wind data: {uMin: -21.32, uMax: 26.8, vMin: -21.57, vMax: 21.42, rows: 181, cols: 360, data: Array(2)}
Wind layers initialized successfully

Layer Toggle:

// When unchecking particle layer
(Removes layer from map)

// When checking particle layer
(Adds layer back to map)

---

🔧 Manual Testing

Test in Browser Console

// 1. Check if map has wind layers
map.getLayer('wind-particles')  // Should return layer object
map.getLayer('wind-heatmap')    // Should return layer object

// 2. Check if map instance is valid
map.loaded()  // Should return true

// 3. Manually toggle layers
map.removeLayer('wind-particles')
map.addLayer(particleLayer)  // If you have reference

---

📝 Code Review Checklist

WindVisualisation.svelte

• Uses $props() (Svelte 5 syntax)
• Has prepareWindData() function
• Waits for map load
• Has error handling (try/catch)
• Cleans up on destroy
• Reactive $effect() for toggles

Map.svelte

• Imports WindVisualization component
• Fetches wind data from testVelo.json
• Passes map and windData props
• Renders WindVisualization component

types.ts

• Supports 3D coordinates [lat, lng, alt]
• Optional alt in LatLngLiteral
• Proper LatLngExpression type

---

🚀 Performance Notes

Particle Count Impact

// High performance (2000-3000 particles)
numParticles: 2000

// Balanced (5000 particles) - Default
numParticles: 5000

// High quality (10000+ particles) - May lag on slower devices
numParticles: 10000

Large Datasets

Current dataset: 65,160 points (360 × 181 grid)

• Should render in <1 second
• GPU-accelerated via WebGL
• No lag on modern browsers

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📚 Additional Resources

• Wind Layer Repo: https://github.com/sakitam-fdd/wind-layer
• MapLibre Docs: https://maplibre.org/maplibre-gl-js/docs/
• Issue Tracker: Report bugs in wind-layer repo

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✅ Final Checklist

Before reporting an issue, verify:

• Dev server running (npm run dev)
• No errors in terminal
• Browser console open (F12)
• No red errors in console
• testVelo.json file exists
• MapLibre GL loaded correctly
• Wind layer package installed
• Component props passed correctly
• SSR disabled for map routes

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Last Updated: December 2025 Status: ✅ Implementation Complete Known Issues: None