diff --git a/88-tar1090.conf b/88-tar1090.conf
index bf545af..1a1cb2f 100644
--- a/88-tar1090.conf
+++ b/88-tar1090.conf
@@ -49,6 +49,12 @@ $HTTP["url"] =~ "^/INSTANCE/data/traces/" {
         "Content-Encoding" => "gzip",
         )
 }
+$HTTP["url"] =~ "^/INSTANCE/data/heatmap/" {
+    setenv.add-response-header += (
+        "Cache-Control" => "public, max-age=10",
+        "Content-Encoding" => "gzip",
+        )
+}
 $HTTP["url"] =~ "^/INSTANCE/data/icao_.*\.json$" {
     setenv.add-response-header += (
         "Cache-Control" => "public, max-age=10",
diff --git a/html/early.js b/html/early.js
index 0a79bc1..eda98be 100644
--- a/html/early.js
+++ b/html/early.js
@@ -17,6 +17,7 @@ let globeIndex = 0;
 let regCache = {};
 let l3harris = false;
 let heatmap = false;
+let heatLocal = false;
 let heatLoaded = 0;
 let heatmapDefer = $.Deferred();
 let heatChunks = [];
@@ -57,7 +58,10 @@ try {
     if (search.has('L3Harris') || search.has('l3harris'))
         l3harris = true;
 
-    if (search.has('heatmap')) {
+    if (search.has('heatmap') || search.has('heatLocal')) {
+
+        if (search.has('heatLocal'))
+            heatLocal = true;
 
         heatmap = {};
 
@@ -143,7 +147,11 @@ if (!heatmap) {
         let zDate = zDateString(time);
         let index = 2 * time.getUTCHours() + Math.floor(time.getUTCMinutes() / 30);
 
-        let URL = "globe_history/" + zDate + "/heatmap/" +
+        let base = "globe_history/";
+        if (heatLocal)
+            base = "data/heatmap/";
+
+        let URL = base + zDate + "/heatmap/" +
             index.toString().padStart(2, '0') + ".bin.ttf";
         let req = $.ajax({
             url: URL,
@@ -201,7 +209,7 @@ if (uuid != null) {
         Dump1090Version = data.version;
         RefreshInterval = data.refresh;
         nHistoryItems = (data.history < 2) ? 0 : data.history;
-        if (data.globeIndexGrid != null) {
+        if (data.globeIndexGrid != null || heatLocal) {
                 HistoryChunks = false;
                 nHistoryItems = 0;
                 globeIndex = 1;
@@ -232,7 +240,7 @@ if (uuid != null) {
 
 function get_history() {
 
-    if (!receiverJson.globeIndexGrid) {
+    if (!globeIndex) {
         nHistoryItems++;
         let request = $.ajax({ url: 'data/aircraft.json',
             timeout: historyTimeout*800,
diff --git a/html/script.js b/html/script.js
index c01eb9c..c29d782 100644
--- a/html/script.js
+++ b/html/script.js
@@ -282,7 +282,7 @@ function processReceiverUpdate(data, init) {
     // Loop through all the planes in the data packet
     let acs = data.aircraft;
 
-    if (!uat && !init && !globeIndex) {
+    if (!uat && !init && !globeIndex && !heatLocal) {
         // Detect stats reset
         if (MessageCountHistory.length > 0 && MessageCountHistory[MessageCountHistory.length-1].messages > data.messages) {
             MessageCountHistory = [{'time' : MessageCountHistory[MessageCountHistory.length-1].time,
@@ -4611,13 +4611,29 @@ function drawHeatmap() {
     for (let k = 0; k < heatChunks.length; k++) {
         if (heatPoints[k] != null) {
             true; // do nothing
-        } else if (heatChunks[k] != null && heatChunks[k].byteLength % 16 == 0) {
-            heatPoints[k] = new Int32Array(heatChunks[k]);
+        } else if (heatChunks[k] != null) {
+            if (heatChunks[k].byteLength % 16 != 0) {
+                console.log("Invalid heatmap file (byteLength): " + k);
+                continue;
+            }
+            let points = heatPoints[k] = new Int32Array(heatChunks[k]);
+            let found = 0;
+            for (let i = 0; i < points.length; i += 4) {
+                if (points[i] == 0xe7f7c9d) {
+                    found = 1;
+                    break;
+                }
+            }
+            if (!found) {
+                heatPoints[k] = heatChunks[k] = null;
+                console.log("Invalid heatmap file (magic number): " + k);
+            }
         } else {
             continue;
         }
         tempPoints.push(heatPoints[k]);
     }
+    //console.log('tempPoints.length: ' + tempPoints.length);
     let myPoints = [];
     if (tempPoints.length <= 2) {
         myPoints = tempPoints;
@@ -4638,11 +4654,15 @@ function drawHeatmap() {
     }
     myPoints = myPoints.flat();
 
+    //console.log('myPoints.length: ' + myPoints.length);
+
     let indexes = [];
     for (let k = 0; k < myPoints.length; k++) {
         let points = myPoints[k];
         let index = [];
         let i = 0;
+        if (!points)
+            continue;
         while(points[i] != 0xe7f7c9d && i < points.length) {
             index.push(points[i]);
             //console.log(points[i]);
@@ -4667,6 +4687,10 @@ function drawHeatmap() {
             if (points[i] == 0xe7f7c9d)
                 i += 4;
 
+            if (i < 0) {
+                console.log('wat ' + i);
+                break;
+            }
             for (; i < points.length; i += 4) {
                 if (points[i] == 0xe7f7c9d)
                     break;
@@ -4699,6 +4723,7 @@ function drawHeatmap() {
                     continue;
 
                 pointCount++;
+                console.log(pos);
 
                 alt = calcAltitudeRounded(alt);
                 let projHere = ol.proj.fromLonLat(pos);
@@ -4740,8 +4765,8 @@ function drawHeatmap() {
         realHeatFeatures.addFeatures(features);
     } else {
         for (let i = 0; i < 16; i++) {
-            //console.log(features.length);
-            heatFeatures[i].addFeatures(features.splice(0, pointCount / 16));
+            heatFeatures[i].addFeatures(features.splice(0, pointCount / 16 + 1));
+            console.log(features.length);
         }
     }
     console.timeEnd("drawHeat");
diff --git a/nginx.conf b/nginx.conf
index 663afb6..a99fe31 100644
--- a/nginx.conf
+++ b/nginx.conf
@@ -21,6 +21,11 @@ location /INSTANCE/data/ {
     add_header Cache-Control "public, max-age=0";
     add_header Content-Encoding "gzip";
   }
+  location /INSTANCE/data/heatmap/ {
+      gzip off;
+      add_header Cache-Control "public, max-age=5";
+      add_header Content-Encoding "gzip";
+  }
 }
 
 location /INSTANCE/globe_history/ {