diff --git a/src/TTN/packed_decoder.js b/src/TTN/packed_decoder.js
index 6db312a4..5b7c1811 100644
--- a/src/TTN/packed_decoder.js
+++ b/src/TTN/packed_decoder.js
@@ -151,11 +151,8 @@ var altitude = function (bytes) {
     if (bytes.length !== altitude.BYTES) {
         throw new Error('Altitude must have exactly 2 bytes');
     }
-    var alt = bytesToInt(bytes);
-    if (alt > 32767) {
-        alt -= 65536;
-    }
-    return alt;
+    var alt = bytesToInt(bytes) / 4 - 1000;
+    return +alt.toFixed(1);
 };
 altitude.BYTES = 2;
 
diff --git a/src/TTN/plain_decoder.js b/src/TTN/plain_decoder.js
index 96655ee7..c6eba7b4 100644
--- a/src/TTN/plain_decoder.js
+++ b/src/TTN/plain_decoder.js
@@ -20,7 +20,7 @@ function Decoder(bytes, port) {
       decoded.longitude = ((bytes[i++] << 24) | (bytes[i++] << 16) | (bytes[i++] << 8) | bytes[i++]);
       decoded.sats = bytes[i++];
       decoded.hdop = (bytes[i++] << 8) | (bytes[i++]);
-      decoded.altitude = (bytes[i++] << 8) | (bytes[i++]);
+      decoded.altitude = ((bytes[i++] << 8) | (bytes[i++])) / 4 - 1000;
     }
   }
 
@@ -41,7 +41,7 @@ function Decoder(bytes, port) {
     decoded.longitude = ((bytes[i++] << 24) | (bytes[i++] << 16) | (bytes[i++] << 8) | bytes[i++]);
     decoded.sats = bytes[i++];
     decoded.hdop = (bytes[i++] << 8) | (bytes[i++]);
-    decoded.altitude = (bytes[i++] << 8) | (bytes[i++]);
+    decoded.altitude = ((bytes[i++] << 8) | (bytes[i++])) / 4 - 1000;
   }
 
   if (port === 5) {
diff --git a/src/gpsread.cpp b/src/gpsread.cpp
index d99a7c46..33ba301a 100644
--- a/src/gpsread.cpp
+++ b/src/gpsread.cpp
@@ -71,7 +71,7 @@ void gps_storelocation(gpsStatus_t &gps_store) {
   gps_store.longitude = (int32_t)(gps.location.lng() * 1e6);
   gps_store.satellites = (uint8_t)gps.satellites.value();
   gps_store.hdop = (uint16_t)gps.hdop.value();
-  gps_store.altitude = (int16_t)gps.altitude.meters();
+  gps_store.altitude = (int16_t)((gps.altitude.meters() + 1000) * 4);
 }
 
 // store current GPS timedate in struct