diff --git a/dump978/Makefile b/dump978/Makefile
index 2d4aebb3..6645fdc3 100644
--- a/dump978/Makefile
+++ b/dump978/Makefile
@@ -1,4 +1,4 @@
-CFLAGS+=-O2 -g -Wall -Werror -Ifec
+CFLAGS+=-O2 -Wall -Werror -Ifec
 LDFLAGS=
 LIBS=-lm
 CC=gcc
diff --git a/image/spindle/wheezy-stage4 b/image/spindle/wheezy-stage4
index 5a547a5e..d372e81a 100755
--- a/image/spindle/wheezy-stage4
+++ b/image/spindle/wheezy-stage4
@@ -135,7 +135,6 @@ cd stratux
 make www
 make xdump978
 make xdump1090
-cp -f dump978/dump978 /usr/bin/
 cp -f dump1090/dump1090 /usr/bin/
 
 mv /tmp/gen_gdl90 /usr/bin/gen_gdl90
diff --git a/main/gen_gdl90.go b/main/gen_gdl90.go
index 50ff54de..a3b17bd6 100644
--- a/main/gen_gdl90.go
+++ b/main/gen_gdl90.go
@@ -349,7 +349,7 @@ func makeOwnshipGeometricAltitudeReport() bool {
 /*
 
 	"SX" Stratux GDL90 message.
-	http://hiltonsoftware.com/stratux/StratuxStatusMessage-V01.pdf
+	http://hiltonsoftware.com/stratux/ for latest version (currently using V104)
 
 */
 
@@ -492,7 +492,7 @@ func makeSXHeartbeat() []byte {
 	v := uint16(float32(10.0) * globalStatus.CPUTemp)
 
 	msg[26] = byte((v & 0xFF00) >> 8)
-	msg[27] = byte(v * 0xFF)
+	msg[27] = byte(v & 0xFF)
 
 	// Number of ADS-B towers.
 	num_towers := uint8(len(ADSBTowers))
diff --git a/main/traffic.go b/main/traffic.go
index 05765cb8..0fac4465 100644
--- a/main/traffic.go
+++ b/main/traffic.go
@@ -442,7 +442,7 @@ func esListen() {
 
 			//FIXME: Some stale information will be renewed.
 			valid_change := true
-			if x[1] == "3" {
+			if x[1] == "3" { // ES airborne position message. DF17 BDS 0,5.
 				//MSG,3,111,11111,AC2BB7,111111,2015/07/28,03:59:12.363,2015/07/28,03:59:12.353,,5550,,,42.35847,-83.42212,,,,,,0
 				//MSG,3,111,11111,A5D007,111111,          ,            ,          ,            ,,35000,,,42.47454,-82.57433,,,0,0,0,0
 				alt := x[11]
@@ -478,7 +478,7 @@ func esListen() {
 					ti.Position_valid = true
 				}
 			}
-			if x[1] == "4" {
+			if x[1] == "4" { // ES airborne velocity message. DF17 BDS 0,9.
 				// MSG,4,111,11111,A3B557,111111,2015/07/28,06:13:36.417,2015/07/28,06:13:36.398,,,414,278,,,-64,,,,,0
 				speed := x[12]
 				track := x[13]
@@ -513,7 +513,7 @@ func esListen() {
 					ti.Speed_valid = true
 				}
 			}
-			if x[1] == "1" {
+			if x[1] == "1" { // ES identification and category. DF17 BDS 0,8.
 				// MSG,1,,,%02X%02X%02X,,,,,,%s,,,,,,,,0,0,0,0
 				tail := x[10]
 
@@ -525,6 +525,16 @@ func esListen() {
 					ti.Tail = tail
 				}
 			}
+			if x[1] == "5" { // Surveillance alt message. DF4, DF20.
+				// MSG,5,,,%02X%02X%02X,,,,,,,%d,,,,,,,%d,%d,%d,%d
+				// MSG,5,111,11111,AB5F1B,111111,2016/01/03,04:43:52.028,2016/01/03,04:43:52.006,,13050,,,,,,,0,,0,0
+				alt := x[11]
+
+				altFloat, err := strconv.ParseFloat(alt, 32)
+				if len(alt) != 0 && err == nil {
+					ti.Alt = int32(altFloat)
+				}
+			}
 
 			// Update "last seen" (any type of message, as long as the ICAO addr can be parsed).
 			ti.Last_source = TRAFFIC_SOURCE_1090ES