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@ -24,6 +24,7 @@
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from __future__ import absolute_import, print_function, division
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from pyModeS.decoder import common
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def airborne_position(msg0, msg1, t0, t1):
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"""Decode airborn position from a pair of even and odd position message
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@ -40,6 +41,16 @@ def airborne_position(msg0, msg1, t0, t1):
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mb0 = common.hex2bin(msg0)[32:]
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mb1 = common.hex2bin(msg1)[32:]
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oe0 = int(mb0[21])
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oe1 = int(mb1[21])
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if oe0 == 0 and oe1 == 1:
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pass
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elif oe0 == 1 and oe1 == 0:
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mb0, mb1 = mb1, mb0
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t0, t1 = t1, t0
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else:
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raise RuntimeError("Both even and odd CPR frames are required.")
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# 131072 is 2^17, since CPR lat and lon are 17 bits each.
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cprlat_even = common.bin2int(mb0[22:39]) / 131072.0
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cprlon_even = common.bin2int(mb0[39:56]) / 131072.0
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@ -66,17 +77,17 @@ def airborne_position(msg0, msg1, t0, t1):
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return None
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# compute ni, longitude index m, and longitude
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if (t0 > t1):
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if t0 > t1:
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lat = lat_even
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nl = common.cprNL(lat)
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ni = max(common.cprNL(lat)- 0, 1)
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m = common.floor(cprlon_even * (nl-1) - cprlon_odd * nl + 0.5)
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ni = max(common.cprNL(lat) - 0, 1)
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m = common.floor(cprlon_even * (nl - 1) - cprlon_odd * nl + 0.5)
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lon = (360.0 / ni) * (m % ni + cprlon_even)
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else:
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lat = lat_odd
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nl = common.cprNL(lat)
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ni = max(common.cprNL(lat) - 1, 1)
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m = common.floor(cprlon_even * (nl-1) - cprlon_odd * nl + 0.5)
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m = common.floor(cprlon_even * (nl - 1) - cprlon_odd * nl + 0.5)
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lon = (360.0 / ni) * (m % ni + cprlon_odd)
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if lon > 180:
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@ -100,17 +111,17 @@ def airborne_position_with_ref(msg, lat_ref, lon_ref):
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(float, float): (latitude, longitude) of the aircraft
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"""
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mb = common.hex2bin(msg)[32:]
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cprlat = common.bin2int(mb[22:39]) / 131072.0
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cprlon = common.bin2int(mb[39:56]) / 131072.0
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i = int(mb[21])
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d_lat = 360.0/59 if i else 360.0/60
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d_lat = 360.0 / 59 if i else 360.0 / 60
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j = common.floor(lat_ref / d_lat) \
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+ common.floor(0.5 + ((lat_ref % d_lat) / d_lat) - cprlat)
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j = common.floor(lat_ref / d_lat) + common.floor(
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0.5 + ((lat_ref % d_lat) / d_lat) - cprlat
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)
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lat = d_lat * (j + cprlat)
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@ -121,8 +132,9 @@ def airborne_position_with_ref(msg, lat_ref, lon_ref):
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else:
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d_lon = 360.0
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m = common.floor(lon_ref / d_lon) \
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+ common.floor(0.5 + ((lon_ref % d_lon) / d_lon) - cprlon)
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m = common.floor(lon_ref / d_lon) + common.floor(
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0.5 + ((lon_ref % d_lon) / d_lon) - cprlon
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)
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lon = d_lon * (m + cprlon)
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@ -141,7 +153,7 @@ def altitude(msg):
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tc = common.typecode(msg)
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if tc<9 or tc==19 or tc>22:
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if tc < 9 or tc == 19 or tc > 22:
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raise RuntimeError("%s: Not a airborn position message" % msg)
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mb = common.hex2bin(msg)[32:]
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@ -150,7 +162,7 @@ def altitude(msg):
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# barometric altitude
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q = mb[15]
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if q:
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n = common.bin2int(mb[8:15]+mb[16:20])
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n = common.bin2int(mb[8:15] + mb[16:20])
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alt = n * 25 - 1000
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else:
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alt = None
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