diff --git a/firmware/application/apps/ui_adsb_rx.cpp b/firmware/application/apps/ui_adsb_rx.cpp
index ba080481..66b7900b 100644
--- a/firmware/application/apps/ui_adsb_rx.cpp
+++ b/firmware/application/apps/ui_adsb_rx.cpp
@@ -205,7 +205,7 @@ void ADSBRxView::on_frame(const ADSBFrameMessage * message) {
 	auto frame = message->frame;
 	uint32_t ICAO_address = frame.get_ICAO_address();
 
-	if (frame.check_CRC() && frame.get_ICAO_address()) {
+	if (frame.check_CRC() && ICAO_address) {
 		rtcGetTime(&RTCD1, &datetime);
 		auto& entry = ::on_packet(recent, ICAO_address);
 		frame.set_rx_timestamp(datetime.minute() * 60 + datetime.second());
@@ -222,11 +222,14 @@ void ADSBRxView::on_frame(const ADSBFrameMessage * message) {
 			uint8_t msg_sub = frame.get_msg_sub();
 			uint8_t * raw_data = frame.get_raw_data();
 			
-			if ((msg_type >= 1) && (msg_type <= 4)) {
+			if ((msg_type >= AIRCRAFT_ID_L) && (msg_type <= AIRCRAFT_ID_H)) {
 				callsign = decode_frame_id(frame);
 				entry.set_callsign(callsign);
 				logentry+=callsign+" ";
-			} else if (((msg_type >= 9) && (msg_type <= 18)) || ((msg_type >= 20) && (msg_type <= 22))) {
+			} 
+			// 
+			else if (((msg_type >= AIRBORNE_POS_BARO_L) && (msg_type <= AIRBORNE_POS_BARO_H)) || 
+				((msg_type >= AIRBORNE_POS_GPS_L) && (msg_type <= AIRBORNE_POS_GPS_H))) {
 				entry.set_frame_pos(frame, raw_data[6] & 4);
 				
 				if (entry.pos.valid) {
@@ -242,7 +245,7 @@ void ADSBRxView::on_frame(const ADSBFrameMessage * message) {
 					if (send_updates)
 						details_view->update(entry);
 				}
-			} else if(msg_type == 19 && msg_sub >= 1 && msg_sub <= 4){
+			} else if(msg_type == AIRBORNE_VEL && msg_sub >= VEL_GND_SUBSONIC && msg_sub <= VEL_AIR_SUPERSONIC){
 				entry.set_frame_velo(frame);
 				logentry += "Type:" + to_string_dec_uint(msg_sub) +
 							" Hdg:" + to_string_dec_uint(entry.velo.heading) +
diff --git a/firmware/application/apps/ui_adsb_rx.hpp b/firmware/application/apps/ui_adsb_rx.hpp
index bb474e83..a63b7eb2 100644
--- a/firmware/application/apps/ui_adsb_rx.hpp
+++ b/firmware/application/apps/ui_adsb_rx.hpp
@@ -36,9 +36,33 @@ using namespace adsb;
 
 namespace ui {
 
-#define ADSB_DECAY_A 10		// In seconds
-#define ADSB_DECAY_B 30
-#define ADSB_DECAY_C 60		// Can be used for removing old entries, RecentEntries already caps to 64
+#define ADSB_DECAY_A 		10		// In seconds
+#define ADSB_DECAY_B 		30
+#define ADSB_DECAY_C 		60		// Can be used for removing old entries, RecentEntries already caps to 64
+
+#define AIRCRAFT_ID_L		1		// aircraft ID message type (lowest type id)
+#define AIRCRAFT_ID_H		4		// aircraft ID message type (highest type id)
+
+#define SURFACE_POS_L		5		// surface position (lowest type id)
+#define SURFACE_POS_H		8		// surface position (highest type id)
+
+#define AIRBORNE_POS_BARO_L	9		// airborne position (lowest type id)
+#define AIRBORNE_POS_BARO_H	18		// airborne position (highest type id)
+
+#define AIRBORNE_VEL		19		// airborne velocities
+
+#define AIRBORNE_POS_GPS_L	20		// airborne position (lowest type id)
+#define AIRBORNE_POS_GPS_H	22		// airborne position (highest type id)
+
+#define RESERVED_L			23		// reserved for other uses
+#define RESERVED_H			31		// reserved for other uses
+
+#define VEL_GND_SUBSONIC		1
+#define VEL_GND_SUPERSONIC		2
+#define VEL_AIR_SUBSONIC		3
+#define VEL_AIR_SUPERSONIC		4
+
+#define O_E_FRAME_TIMEOUT		20	// timeout between odd and even frames
 
 struct AircraftRecentEntry {
 	using Key = uint32_t;
@@ -82,7 +106,7 @@ struct AircraftRecentEntry {
 			frame_pos_odd = frame;
 		
 		if (!frame_pos_even.empty() && !frame_pos_odd.empty()) {
-			if (abs(frame_pos_even.get_rx_timestamp() - frame_pos_odd.get_rx_timestamp()) < 20)
+			if (abs(frame_pos_even.get_rx_timestamp() - frame_pos_odd.get_rx_timestamp()) < O_E_FRAME_TIMEOUT)
 				pos = decode_frame_pos(frame_pos_even, frame_pos_odd);
 		}
 	}
diff --git a/firmware/common/adsb.cpp b/firmware/common/adsb.cpp
index 862e375d..335c6d21 100644
--- a/firmware/common/adsb.cpp
+++ b/firmware/common/adsb.cpp
@@ -141,7 +141,11 @@ float cpr_mod(float a, float b) {
 	return a - (b * floor(a / b));
 }
 
-int cpr_NL(float lat) {
+int cpr_NL_precise(float lat) {
+	return (int) floor(2 * PI / acos(1 - ((1 - cos(PI / (2 * NZ))) / pow(cos(PI * lat / 180), 2))));
+}
+
+int cpr_NL_approx(float lat) {
 	if (lat < 0)
 		lat = -lat;		// Symmetry
 	
@@ -150,7 +154,11 @@ int cpr_NL(float lat) {
 			return 59 - c;
 	}
 	
-	return 1;
+	return 1;	
+}
+
+int cpr_NL(float lat) {
+	return cpr_NL_precise(lat);
 }
 
 int cpr_N(float lat, int is_odd) {
@@ -258,7 +266,7 @@ adsb_pos decode_frame_pos(ADSBFrame& frame_even, ADSBFrame& frame_odd) {
 
 	// Compute longitude
 	if (time_even > time_odd) {
-		// Use even frame
+		// Use even frame2
 		ni = cpr_N(latE, 0);
 		Dlon = 360.0 / ni;
 		
@@ -279,7 +287,7 @@ adsb_pos decode_frame_pos(ADSBFrame& frame_even, ADSBFrame& frame_odd) {
 		position.latitude = latO;
 	}
 	
-	if (position.longitude > 180) position.longitude -= 360;
+	if (position.longitude >= 180) position.longitude -= 360;
 	
 	position.valid = true;
 
diff --git a/firmware/common/adsb.hpp b/firmware/common/adsb.hpp
index 82d177e4..f3a2f3ac 100644
--- a/firmware/common/adsb.hpp
+++ b/firmware/common/adsb.hpp
@@ -83,6 +83,10 @@ const float adsb_lat_lut[58] = {
     86.53536998,    87.00000000
 };
 
+const float PI = 3.14159265358979323846;
+
+const float NZ = 15;
+
 void make_frame_adsb(ADSBFrame& frame, const uint32_t ICAO_address);
 
 void encode_frame_id(ADSBFrame& frame, const uint32_t ICAO_address, const std::string& callsign);