Increased GPS altitude resolution

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;
 

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) {