major update; adsb restructure; rename combining util/modes to common.

pyModeS/decoder/bds/bds09.py

@@ -0,0 +1,116 @@
+# Copyright (C) 2018 Junzi Sun (TU Delft)
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+"""
+------------------------------------------
+  BDS 0,9
+  ADS-B TC=19
+  Aircraft Airborn velocity
+------------------------------------------
+"""
+
+from __future__ import absolute_import, print_function, division
+from pyModeS.decoder import common
+import math
+
+
+def airborne_velocity(msg):
+    """Calculate the speed, track (or heading), and vertical rate
+
+    Args:
+        msg (string): 28 bytes hexadecimal message string
+
+    Returns:
+        (int, float, int, string): speed (kt), ground track or heading (degree),
+            rate of climb/descend (ft/min), and speed type
+            ('GS' for ground speed, 'AS' for airspeed)
+    """
+
+    if common.typecode(msg) != 19:
+        raise RuntimeError("%s: Not a airborne velocity message, expecting TC=19" % msg)
+
+    mb = common.hex2bin(msg)[32:]
+
+    subtype = common.bin2int(mb[5:8])
+
+    if common.bin2int(mb[14:24]) == 0 or common.bin2int(mb[25:35]) == 0:
+        return None
+
+    if subtype in (1, 2):
+        v_ew_sign = -1 if mb[13]=='1' else 1
+        v_ew = common.bin2int(mb[14:24]) - 1       # east-west velocity
+
+        v_ns_sign = -1 if mb[24]=='1' else 1
+        v_ns = common.bin2int(mb[25:35]) - 1       # north-south velocity
+
+
+        v_we = v_ew_sign * v_ew
+        v_sn = v_ns_sign * v_ns
+
+        spd = math.sqrt(v_sn*v_sn + v_we*v_we)  # unit in kts
+
+        trk = math.atan2(v_we, v_sn)
+        trk = math.degrees(trk)                 # convert to degrees
+        trk = trk if trk >= 0 else trk + 360    # no negative val
+
+        tag = 'GS'
+        trk_or_hdg = trk
+
+    else:
+        if mb[13] == '0':
+            hdg = None
+        else:
+            hdg = common.bin2int(mb[14:24]) / 1024.0 * 360.0
+
+        trk_or_hdg = hdg
+
+        spd = common.bin2int(mb[25:35])
+        spd = None if spd==0 else spd-1
+
+        if mb[24]=='0':
+            tag = 'IAS'
+        else:
+            tag = 'TAS'
+
+    vr_sign = -1 if mb[36]=='1' else 1
+    vr = common.bin2int(mb[37:46])
+    rocd = None if vr==0 else vr_sign*(vr-1)*64
+
+    return int(spd), round(trk_or_hdg, 2), int(rocd), tag
+
+def altitude_diff(msg):
+    """Decode the differece between GNSS and barometric altitude
+
+    Args:
+        msg (string): 28 bytes hexadecimal message string, TC=19
+
+    Returns:
+        int: Altitude difference in ft. Negative value indicates GNSS altitude
+            below barometric altitude.
+    """
+    tc = common.typecode(msg)
+
+    if tc != 19:
+        raise RuntimeError("%s: Not a airborne velocity message, expecting TC=19" % msg)
+
+    msgbin = common.hex2bin(msg)
+    sign = -1 if int(msgbin[80]) else 1
+    value = common.bin2int(msgbin[81:88])
+
+    if value == 0 or value == 127:
+        return None
+    else:
+        return sign * (value - 1) * 25    # in ft.