FGFS-4.1/gr-air-modes
4
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

CPR test case hugely expanded. Found bug in global decoding in the Southern Hemisphere. Haven't fixed the bug yet.

Browse Source
This commit is contained in:
Nick Foster 2012-06-15 19:34:03 -07:00
parent f9026feb7f
commit c6ab762ee0
2 changed files with 38 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
apps/get_correlated_records.py
View File

@ -1,6 +1,5 @@
#!/usr/bin/env python
from modes_parse import modes_parse
import mlat
from air_modes import modes_parse, mlat
import numpy
import sys
@ -10,7 +9,7 @@ import sys
#sfoutfile = open("sfout.txt", "w")
#rudioutfile = open("rudiout.txt", "w")
sfparse = modes_parse([37.762236,-122.442525])
sfparse = modes_parse.modes_parse([37.762236,-122.442525])
sf_station = [37.762236,-122.442525, 100]
mv_station = [37.409348,-122.07732, 100]

60
python/cpr.py
View File

@ -1,5 +1,6 @@
#!/usr/bin/env python
#
# Copyright 2010 Nick Foster
# Copyright 2010, 2012 Nick Foster
#
# This file is part of gr-air-modes
#
@ -19,8 +20,6 @@
# Boston, MA 02110-1301, USA.
#
#!/usr/bin/env python
#from string import split, join
#from math import pi, floor, cos, acos
import math, time
@ -56,8 +55,10 @@ def nl_eo(declat_in, ctype):
return nl(declat_in) - ctype
def nl(declat_in):
if declat_in == 0:
declat_in = 0.01
if declat_in >= 87.0:
declat_in = 86.999999999
if declat_in <= -87.0:
declat_in = -86.999999999
return math.floor( (2.0*math.pi) * pow(math.acos(1.0- (1.0-math.cos(math.pi/(2.0*latz))) / pow( math.cos( (math.pi/180.0)*abs(declat_in) ) ,2.0) ),-1.0))
def dlon(declat_in, ctype, surface):
@ -264,34 +265,41 @@ def cpr_encode(lat, lon, ctype, surface):
return (yz, xz) #lat, lon
if __name__ == '__main__':
from modes_parse import *
import sys
import sys, random
my_location = [37.76225, -122.44254]
rounds = 100
threshold = 1e-3 #0.001 deg lat/lon
#this accuracy is highly dependent on latitude, since at high
#latitudes the corresponding error in longitude is greater
shortdata = long(sys.argv[1], 16)
longdata = long(sys.argv[2], 16)
parity = long(sys.argv[3], 16)
ecc = long(sys.argv[4], 16)
decoder = cpr_decoder(None)
parser = modes_parse(my_location)
for i in range(0, rounds):
ac_lat = random.uniform(-87,87)
ac_lon = random.uniform(-180,180)
[altitude, decoded_lat, decoded_lon, rnge, bearing] = parser.parseBDS06(shortdata, longdata, parity, ecc)
#encode that position
(evenenclat, evenenclon) = cpr_encode(ac_lat, ac_lon, False, False)
(oddenclat, oddenclon) = cpr_encode(ac_lat, ac_lon, True, False)
if decoded_lat is not None:
print "Altitude: %i\nLatitude: %.6f\nLongitude: %.6f\nRange: %.2f\nBearing: %i\n" % (altitude, decoded_lat, decoded_lon, rnge, bearing,)
#perform a global decode
icao = random.randint(0, 0xffffff)
evenpos = decoder.decode(icao, evenenclat, evenenclon, False, False)
if evenpos != [None, None, None, None]:
raise Exception("CPR test failure: global decode with only one report")
(odddeclat, odddeclon, rng, brg) = decoder.decode(icao, oddenclat, oddenclon, True, False)
print "Decomposing...\n"
if odddeclat is None: #boundary straddle, just move on
continue
subtype = (longdata >> 51) & 0x1F;
if abs(odddeclat - ac_lat) > threshold or abs(odddeclon - ac_lon) > threshold:
print "Global decode error: Lat: %f Lon: %f Decoded lat: %f lon: %f" % (ac_lat, ac_lon, odddeclat, odddeclon)
#raise Exception("CPR test failure: global decode error greater than threshold")
encoded_lon = longdata & 0x1FFFF
encoded_lat = (longdata >> 17) & 0x1FFFF
cpr_format = (longdata >> 34) & 1
(evendeclat, evendeclon) = cpr_resolve_local([ac_lat, ac_lon], [evenenclat, evenenclon], False, False)
enc_alt = (longdata >> 36) & 0x0FFF
if abs(evendeclat - ac_lat) > threshold or abs(evendeclon - ac_lon) > threshold:
print "Local decode error: Lat: %f Lon: %f Decoded lat: %f lon: %f" % (ac_lat, ac_lon, evendeclat, evendeclon)
#raise Exception("CPR test failure: local decode error greater than threshold")
[cpr_lat, cpr_lon] = cpr_resolve_local(my_location, [encoded_lat, encoded_lon], cpr_format, 1)
print "Subtype: %i\nEncoded longitude: %x\nEncoded latitude: %x\nCPR format: %i\nEncoded altitude: %x\n" % (subtype, encoded_lon, encoded_lat, cpr_format, enc_alt,)
print "Pos: %.6f %.6f" % (cpr_lat, cpr_lon)
print "CPR test successful."