feat: Implement heatmap visualization for device density

- Add Leaflet.heat plugin (leaflet-heat.js)
- Create renderHeatmap() function with confidence-based intensity
- Toggle between markers and heatmap view
- Support frequency filtering in heatmap mode
- Custom gradient: blue -> cyan -> lime -> yellow -> red
- Configurable radius (25px), blur (15px), and maxZoom (17)
- Console logging for debugging heatmap rendering
- Intensity based on device match confidence (0.5 default)

static/js/map.js

@@ -3,7 +3,9 @@
 let map;
 let markerLayer;
 let markerClusterGroup;
+let heatmapLayer;
 let capturesData = [];
+let heatmapEnabled = false;
 
 // Frequency color mapping
 const FREQUENCY_COLORS = {
@@ -64,14 +66,33 @@ function setupMapControls() {
 
     // Frequency filter
     document.getElementById('frequency-filter').addEventListener('change', () => {
-        renderMarkers();
+        if (heatmapEnabled) {
+            renderHeatmap();
+        } else {
+            renderMarkers();
+        }
     });
 
-    // Heatmap toggle (placeholder)
+    // Heatmap toggle
     document.getElementById('heatmap-toggle').addEventListener('change', (e) => {
-        if (e.target.checked) {
-            alert('Heatmap view coming soon!');
-            e.target.checked = false;
+        heatmapEnabled = e.target.checked;
+        if (heatmapEnabled) {
+            // Hide markers, show heatmap
+            map.removeLayer(markerClusterGroup);
+            map.removeLayer(markerLayer);
+            renderHeatmap();
+        } else {
+            // Hide heatmap, show markers
+            if (heatmapLayer) {
+                map.removeLayer(heatmapLayer);
+            }
+            // Re-add appropriate marker layer based on cluster toggle
+            const clusterEnabled = document.getElementById('cluster-toggle').checked;
+            if (clusterEnabled) {
+                map.addLayer(markerClusterGroup);
+            } else {
+                map.addLayer(markerLayer);
+            }
         }
     });
 }
@@ -199,5 +220,57 @@ function updateStats() {
     document.getElementById('unique-devices').textContent = uniqueDevices;
 }
 
+function renderHeatmap() {
+    // Remove existing heatmap layer if it exists
+    if (heatmapLayer) {
+        map.removeLayer(heatmapLayer);
+    }
+
+    // Get frequency filter
+    const frequencyFilter = document.getElementById('frequency-filter').value;
+
+    // Filter captures
+    let filtered = capturesData;
+
+    if (frequencyFilter) {
+        const targetFreq = parseInt(frequencyFilter) * 1e6;
+        filtered = capturesData.filter(c => {
+            const freq = c.frequency / 1e6;
+            return Math.abs(freq - parseInt(frequencyFilter)) < 50;
+        });
+    }
+
+    // Convert captures to heatmap data format
+    // Format: [[lat, lng, intensity], ...]
+    const heatmapData = filtered.map(capture => {
+        // Use match confidence as intensity (default to 0.5 if no match)
+        const intensity = capture.match_confidence || 0.5;
+        return [capture.latitude, capture.longitude, intensity];
+    });
+
+    console.log(`Rendering heatmap with ${heatmapData.length} points`);
+
+    // Create heatmap layer
+    heatmapLayer = L.heatLayer(heatmapData, {
+        radius: 25,           // Radius of each point
+        blur: 15,             // Amount of blur
+        maxZoom: 17,          // Zoom level where max intensity is reached
+        max: 1.0,             // Maximum point intensity
+        gradient: {           // Custom color gradient
+            0.0: 'blue',
+            0.3: 'cyan',
+            0.5: 'lime',
+            0.7: 'yellow',
+            1.0: 'red'
+        }
+    });
+
+    // Add to map
+    map.addLayer(heatmapLayer);
+
+    // Update count
+    document.getElementById('total-captures').textContent = filtered.length;
+}
+
 // Export for external use
 window.reloadMapData = loadCaptures;

templates/index.html

@@ -280,6 +280,7 @@
     <!-- Leaflet JS -->
     <script src="https://unpkg.com/leaflet@1.9.4/dist/leaflet.js"></script>
     <script src="https://unpkg.com/leaflet.markercluster@1.5.3/dist/leaflet.markercluster.js"></script>
+    <script src="https://unpkg.com/leaflet.heat@0.2.0/dist/leaflet-heat.js"></script>
 
     <!-- Chart.js -->
     <script src="https://cdn.jsdelivr.net/npm/chart.js@4.4.1/dist/chart.umd.min.js"></script>