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#!/usr/bin/env python
#
# gps.py -- Python interface to GPSD.
#
import time, socket, sys
from math import *
STATUS_NO_FIX = 0
STATUS_FIX = 1
STATUS_DGPS_FIX = 2
MODE_NO_FIX = 1
MODE_2D = 2
MODE_3D = 3
MAXCHANNELS = 12
SIGNAL_STRENGTH_UNKNOWN = -1
class gpsdata:
"Position, track, velocity and status information returned by a GPS."
class timestamp:
def __init__(self, now):
self.last_refresh = now
self.changed = False
def refresh(self):
self.last_refresh = time.time()
def seen(self):
return self.last_refresh
def __repr__(self):
return "{lr=%d, changed=%s}" % (self.last_refresh, self.changed)
class satellite:
def __init__(self, PRN, elevation, azimuth, ss, used=None):
self.PRN = PRN
self.elevation = elevation
self.azimuth = azimuth
self.ss = ss
self.used = used
def __repr__(self):
return "PRN: %3d E: %3d Az: %3d Ss: %d Used: %s" % (self.PRN,self.elevation,self.azimuth,self.ss,"ny"[self.used])
def __init__(self):
# Initialize all data members
now = time.time()
self.online = False # True if GPS on, False if not
self.online_stamp = gps.timestamp(now)
self.utc = ""
self.latitude = self.longitude = 0.0
self.latlon_stamp = gps.timestamp(now)
self.altitude = 0.0 # Meters
self.altitude_stamp = gps.timestamp(now)
self.speed = 0.0 # Knots
self.speed_stamp = gps.timestamp(now)
self.track = 0.0 # Degrees from true north
self.track_stamp = gps.timestamp(now)
self.status = STATUS_NO_FIX
self.status_stamp = gps.timestamp(now)
self.mode = MODE_NO_FIX
self.mode_stamp = gps.timestamp(now)
self.satellites_used = 0 # Satellites used in last fix
self.pdop = self.hdop = self.vdop = 0.0
self.fix_quality_stamp = gps.timestamp(now)
self.satellites = [] # satellite objects in view
self.satellite_stamp = gps.timestamp(now)
self.await = self.parts = 0
self.tag = ""
self.recv_time = 0
self.length = 0
self.emit_time = 0
self.read_time = 0
self.baudrate = 0
self.stopbits = 0
__setattr__ = setattr
def setattr(self, name, value):
# Make sure the change stamp for each field is kept up to date
group = {'online':'online_stamp',
#'latitude':'latlon_stamp'),
#'longitude':'latlon_stamp',
'altitude':'altitude_stamp',
'speed':'speed_stamp',
'track':'track_stamp',
'status':'status_stamp',
'mode':'mode_stamp',
#'pdop':'fix_quality_stamp',
#'hdop':'fix_quality_stamp',
#'vdop':'fix_quality_stamp',
'satellites':'satellite_stamp',
}
if field in group:
stamp = getattr(self, group[field])
stamp.changed = (getattr(self, field) != value)
stamp.refresh()
self.__dict__[name] = value
def __repr__(self):
st = ""
st += "Lat/lon: %f %f " % (self.latitude, self.longitude)
st += repr(self.latlon_stamp) + "\n"
st += "Altitude: %f " % (self.altitude)
st += repr(self.altitude_stamp) + "\n"
st += "Speed: %f " % (self.speed)
st += repr(self.speed_stamp) + "\n"
st += "Track: %f " % (self.track)
st += repr(self.track_stamp) + "\n"
st += "Status: STATUS_%s" % ("NO_FIX", "FIX","DGPS_FIX")[self.status]
st += " " +repr(self.status_stamp) + "\n"
st += "Mode: MODE_" + ("ZERO", "NO_FIX", "2D","3D")[self.mode]
st += " " + repr(self.mode_stamp) + "\n"
st += "Quality: %d p=%2.2f h=%2.2f v=%2.2f " % \
(self.satellites_used, self.pdop, self.hdop, self.vdop)
st += repr(self.fix_quality_stamp) + "\n"
st += "Y: %s satellites in view:\n" % len(self.satellites)
for sat in self.satellites:
st += " " + repr(sat) + "\n"
st += " " + repr(self.satellite_stamp) + "\n"
return st
class gps(gpsdata):
"Client interface to a running gpsd instance."
def __init__(self, host="localhost", port="2947", verbose=0):
gpsdata.__init__(self)
self.sock = None # in case we blow up in connect
self.sockfile = None
self.connect(host, port)
self.verbose = verbose
self.raw_hook = None
def connect(self, host, port):
"""Connect to a host on a given port.
If the hostname ends with a colon (`:') followed by a number, and
there is no port specified, that suffix will be stripped off and the
number interpreted as the port number to use.
"""
if not port and (host.find(':') == host.rfind(':')):
i = host.rfind(':')
if i >= 0:
host, port = host[:i], host[i+1:]
try: port = int(port)
except ValueError:
raise socket.error, "nonnumeric port"
if not port: port = SMTP_PORT
#if self.debuglevel > 0: print 'connect:', (host, port)
msg = "getaddrinfo returns an empty list"
self.sock = None
self.sockfile = None
for res in socket.getaddrinfo(host, port, 0, socket.SOCK_STREAM):
af, socktype, proto, canonname, sa = res
try:
self.sock = socket.socket(af, socktype, proto)
#if self.debuglevel > 0: print 'connect:', (host, port)
self.sock.connect(sa)
self.sockfile = self.sock.makefile()
except socket.error, msg:
#if self.debuglevel > 0: print 'connect fail:', (host, port)
if self.sock:
self.sock.close()
self.sock = None
self.sockfile = None
continue
break
if not self.sock:
raise socket.error, msg
def set_raw_hook(self, hook):
self.raw_hook = hook
def __del__(self):
if self.sock:
self.sock.close()
self.sock = None
self.sockfile = None
def __unpack(self, buf):
# unpack a daemon response into the instance members
fields = buf.strip().split(",")
if fields[0] == "GPSD":
for field in fields[1:]:
if not field or field[1] != '=':
continue
cmd = field[0]
data = field[2:]
if data[0] == "?":
continue
if cmd in ('A', 'a'):
d1 = float(data)
self.altitude_stamp.changed = (self.altitude != d1)
self.altitude = d1
self.altitude_stamp.refresh()
elif cmd in ('D', 'd'):
self.utc = data
elif cmd in ('M', 'm'):
i1 = int(data)
self.mode_stamp.changed = (self.mode != i1)
self.mode = i1
self.mode_stamp.refresh()
elif cmd in ('P', 'p'):
(f1, f2) = map(float, data.split())
self.latlon_stamp.changed = (self.latitude != f1 or self.longitude != f2)
self.latitude = f1
self.longitude = f2
self.latlon_stamp.refresh()
elif cmd in ('Q', 'q'):
parts = data.split()
i1 = int(parts[0])
(f1, f2, f3) = map(float, parts[1:])
self.fix_quality_stamp.changed = (self.pdop != f1 or self.hdop != f2 or self.vdop != f3)
self.satellites_used = i1
self.pdop = f1
self.hdop = f2
self.vdop = f3
self.fix_quality_stamp.refresh()
elif cmd in ('S', 's'):
i1 = int(data)
self.status_stamp.changed = (self.status != i1)
self.status = i1
self.status_stamp.refresh()
elif cmd in ('T', 't'):
d1 = float(data)
self.track_stamp.changed = (self.track != d1)
self.track = d1
self.track_stamp.refresh()
elif cmd in ('V', 'v'):
d1 = float(data)
self.speed_stamp.changed = (self.speed != d1)
self.speed = d1
self.speed_stamp.refresh()
elif cmd in ('X', 'x'):
b1 = data[0] == '1'
self.online_stamp.changed = (b1 != self.online)
self.online = b1
self.online_stamp.refresh()
elif cmd in ('Y', 'y'):
satellites = data.split(":")
d1 = int(satellites.pop(0))
newsats = []
for i in range(d1):
newsats.append(gps.satellite(*map(int, satellites[i].split())))
self.satellite_stamp.changed = (self.satellites) != newsats
self.satellites = newsats
self.satellite_stamp.refresh()
elif cmd in ('Z', 'z'):
(dummy, self.baudrate, self.stopbits) = map(int, data.split(":"))
elif cmd == '$':
(self.tag, recv_time, length, emit_time) = data.split(":")
self.recv_time = float(recv_time)
self.length = int(length)
self.emit_time = float(emit_time)
self.read_time = time.time()
if self.raw_hook:
self.raw_hook(buf);
return self.online_stamp.changed \
or self.latlon_stamp.changed \
or self.altitude_stamp.changed \
or self.speed_stamp.changed \
or self.track_stamp.changed \
or self.fix_quality_stamp.changed \
or self.fix_quality_stamp.changed \
or self.status_stamp.changed \
or self.mode_stamp.changed \
or self.satellite_stamp.changed
def poll(self):
"Wait for and read data being streamed from gpsd."
data = self.sockfile.readline()
if self.verbose:
sys.stderr.write("GPS DATA %s\n" % repr(data))
return self.__unpack(data)
def query(self, commands):
"Send a command, get back a response."
self.sockfile.write(commands)
self.sockfile.flush()
return self.poll()
# some multipliers for interpreting GPS output
METERS_TO_FEET = 3.2808399
METERS_TO_MILES = 0.00062137119
KNOTS_TO_MPH = 1.1507794
# SirF-II control code
class SiRF:
def transport(payload):
msg = '\xa0'
msg += '\xa2'
msg += chr(len(payload) >> 8)
msg += chr(len(payload) & 0xff)
msg += payload
checksum = 0
for ch in payload:
checksum += ord(ch);
checksum &= 0x7fff
msg += chr((checksum >> 8) & 0xff00)
msg += chr(checksum & 0x00ff)
msg += '\xb0'
msg += '\xb3'
return msg
transport = staticmethod(transport)
def to_NMEA(baudrate):
"Generate a SiRF binary protocol command to switch back to NMEA."
switcher = [
'\x81', # Byte 0 = 0x81: Switch to NMEA command
'\x02', # Byte 1 = 0x02: Leave debug-message switch as it is.
'\x01', # Byte 2 = 0x01: Enable GPGGA at 1-second interval
'\x01', # Byte 3 = 0x01: GPGGA checksum enable
'\x01', # Byte 4 = 0x01: Enable GPGLL at 1-second interval
'\x01', # Byte 5 = 0x01: GPGLL checksum enable
'\x01', # Byte 6 = 0x05: Enable GPGSA at 5-second interval
'\x01', # Byte 7 = 0x01: GPGSA checksum enable
'\x05', # Byte 8 = 0x05: Enable GPGSV at 5-second interval
'\x01', # Byte 9 = 0x01: GPGSV checksum enable
'\x00', # Byte 10 = 0x05: Disable GPMSS
'\x00', # Byte 11 = 0x01: GPMSS checksum disable
'\x01', # Byte 12 = 0x01: Enable GPRMC at 1-second interval
'\x01', # Byte 13 = 0x01: GPRMC checksum enable
'\x01', # Byte 14 = 0x01: Enable GPVTG at 1-second interval
'\x01', # Byte 15 = 0x01: GPVTG checksum enable
'\x00', # Byte 16 = 0x00: Unused
'\x00', # Byte 17 = 0x00: Unused
'\x00', # Byte 18 = 0x00: Unused
'\x00', # Byte 19 = 0x00: Unused
'\x00', # Byte 20 = 0x00: Unused
'\x00', # Byte 21 = 0x00: Unused
]
switcher += [chr(baudrate >> 8), chr(baudrate & 0x0ff)]
return SiRF.transport("".join(switcher))
to_NMEA = staticmethod(to_NMEA)
# EarthDistance code swiped from Kismet and corrected
# (As yet, this stuff is not in the libgps C library.)
def Deg2Rad(x):
"Degrees to radians."
return x * (pi/180)
def CalcRad(lat):
"Radius of curvature in meters at specified latitude."
a = 6378.137
e2 = 0.081082 * 0.081082
# the radius of curvature of an ellipsoidal Earth in the plane of a
# meridian of latitude is given by
#
# R' = a * (1 - e^2) / (1 - e^2 * (sin(lat))^2)^(3/2)
#
# where a is the equatorial radius,
# b is the polar radius, and
# e is the eccentricity of the ellipsoid = sqrt(1 - b^2/a^2)
#
# a = 6378 km (3963 mi) Equatorial radius (surface to center distance)
# b = 6356.752 km (3950 mi) Polar radius (surface to center distance)
# e = 0.081082 Eccentricity
sc = sin(Deg2Rad(lat))
x = a * (1.0 - e2)
z = 1.0 - e2 * sc * sc
y = pow(z, 1.5)
r = x / y
r = r * 1000.0 # Convert to meters
return r
def EarthDistance((lat1, lon1), (lat2, lon2)):
"Distance in meters between two points specified in degrees."
x1 = CalcRad(lat1) * cos(Deg2Rad(lon1)) * sin(Deg2Rad(90-lat1))
x2 = CalcRad(lat2) * cos(Deg2Rad(lon2)) * sin(Deg2Rad(90-lat2))
y1 = CalcRad(lat1) * sin(Deg2Rad(lon1)) * sin(Deg2Rad(90-lat1))
y2 = CalcRad(lat2) * sin(Deg2Rad(lon2)) * sin(Deg2Rad(90-lat2))
z1 = CalcRad(lat1) * cos(Deg2Rad(90-lat1))
z2 = CalcRad(lat2) * cos(Deg2Rad(90-lat2))
a = (x1*x2 + y1*y2 + z1*z2)/pow(CalcRad((lat1+lat2)/2),2)
# a should be in [1, -1] but can sometimes fall outside it by
# a very small amount due to rounding errors in the preceding
# calculations (this is prone to happen when the argument points
# are very close together). Thus we constrain it here.
if abs(a) > 1: a = 1
elif a < -1: a = -1
return CalcRad((lat1+lat2) / 2) * acos(a)
def MeterOffset((lat1, lon1), (lat2, lon2)):
"Return offset in meters of second arg from first."
dx = EarthDistance((lat1, lon1), (lat1, lon2))
dy = EarthDistance((lat1, lon1), (lat2, lon1))
if lat1 < lat2: dy *= -1
if lon1 < lon2: dx *= -1
return (dx, dy)
def isotime(s):
"Convert gpsd timestamps in ISO8661 format to local Unix time, and back."
if type(s) == type(1):
return time.strftime(time.localtime(s), "%Y-%m-%dT%H:%M:%S")
elif type(s) == type(1.0):
date = int(s)
msec = s - date
date = time.strftime("%Y-%m-%dT%H:%M:%S", time.localtime(s))
return date + "." + `msec`[2:]
elif type(s) == type(""):
gmt = s[-1] == "Z"
if gmt:
s = s[:-1]
if "." in s:
(date, msec) = s.split(".")
else:
date = s
msec = "0"
unpacked = time.strptime(date, "%Y-%m-%dT%H:%M:%S")
seconds = time.mktime(unpacked)
uncorrected = seconds + float("0." + msec)
if not time.daylight:
return uncorrected - time.timezone
else:
return uncorrected - time.altzone
else:
raise TypeError
if __name__ == '__main__':
import sys,readline
print "This is the exerciser for the Python gps interface."
session = gps()
session.set_raw_hook(lambda s: sys.stdout.write(s + "\n"))
try:
while True:
commands = raw_input("> ")
session.query(commands)
print session
except EOFError:
print "Goodbye!"
del session
# gps.py ends here
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