我一直在尝试使用python 2.6中的标准 GPS（gps.py）模块。这应该充当客户端并从Ubuntu中运行的gpsd读取GPS数据。
根据GPSD网页上关于客户端设计的文档（GPSD Client Howto），我应该可以使用以下代码（稍微修改一下）获取最新的GPS读数（lat long是我主要是感兴趣的）
from gps import *
session = gps() # assuming gpsd running with default options on port 2947
session.stream(WATCH_ENABLE|WATCH_NEWSTYLE)
report = session.next()
print report
如果我重复使用next（），它会从队列底部（从会话开始时）开始给出缓冲值，而不是LATEST Gps读数。有没有办法使用这个库获取更新的值？在某种程度上，寻求流到最新的价值？
是否有人使用此库获取代码示例来轮询gps并获取我正在寻找的值？
以下是我要做的事情：
答案 0 :(得分：17)
您需要做的是定期轮询'session.next（）' - 这里的问题是您正在处理串行接口 - 您按照收到的顺序获得结果。由您来维护具有最新检索值的'current_value'。
如果您不轮询会话对象，最终您的UART FIFO将填满，无论如何您都不会获得任何新值。
考虑使用一个线程，不要等待用户调用gps_poll（），你应该进行轮询，当用户想要一个新值时，他们使用'get_current_value（）'返回current_value。
在我的脑海中，它可能就像这样简单：
import threading
import time
from gps import *
class GpsPoller(threading.Thread):
def __init__(self):
threading.Thread.__init__(self)
self.session = gps(mode=WATCH_ENABLE)
self.current_value = None
def get_current_value(self):
return self.current_value
def run(self):
try:
while True:
self.current_value = self.session.next()
time.sleep(0.2) # tune this, you might not get values that quickly
except StopIteration:
pass
if __name__ == '__main__':
gpsp = GpsPoller()
gpsp.start()
# gpsp now polls every .2 seconds for new data, storing it in self.current_value
while 1:
# In the main thread, every 5 seconds print the current value
time.sleep(5)
print gpsp.get_current_value()
答案 1 :(得分：3)
对于使用现代版本的gpsd且仅在特定时间需要数据而不是流式传输的人来说，上述答案效率非常低且过于复杂。
大多数GPS每秒至少发送一次位置信息。据推测，由于许多基于GPS的应用程序需要实时更新，我见过的绝大多数gpsd客户端示例都使用上述方法来观看来自gpsd的流并接收实时更新（与gps发送的频率相同或多或少）它们）。
但是，如果（如在OP的情况下）你不需要需要流媒体信息，但只要它被请求就需要最后报告的位置（即通过用户交互或其他一些事件），有一种更高效，更简单的方法：让gpsd缓存最新的位置信息，并在需要时进行查询。
gpsd JSON protocol有一个?WATCH={"enable":true}请求，该请求会返回gpsd看到的最新GPS信息。您可以在gpsd会话开始时发送?POLL;消息，然后在需要时查询最新的位置信息，而不必迭代积压的gps消息，并不断读取新消息以避免使用完整缓冲区。它与import gpsd
gpsd.connect()
packet = gpsd.get_current()
print(packet.position())
。响应是一个JSON对象，包含gpsd从GPS中看到的最新信息。
如果您使用的是Python3，我发现的最简单方法是使用pypi上提供的gpsd-py3软件包。要连接到gpsd，请获取最新的位置信息，然后打印当前位置：
gpsd.get_current()您可以在需要新位置信息时重复?POLL;调用，并且在幕后gpsd包将执行对{gpsd的gps调用并返回表示响应的对象。
使用内置的telnet模块执行此操作并不是非常简单，但是还有许多其他可用的Python客户端，而且对于任何可以使用的内容都很简单。使用$ telnet localhost 2947
Trying ::1...
Connected to localhost.
Escape character is '^]'.
{"class":"VERSION","release":"3.16","rev":"3.16","proto_major":3,"proto_minor":11}
?WATCH={"enable":true}
{"class":"DEVICES","devices":[{"class":"DEVICE","path":"/dev/pts/10","driver":"SiRF","activated":"2018-03-02T21:14:52.687Z","flags":1,"native":1,"bps":4800,"parity":"N","stopbits":1,"cycle":1.00}]}
{"class":"WATCH","enable":true,"json":false,"nmea":false,"raw":0,"scaled":false,"timing":false,"split24":false,"pps":false}
?POLL;
{"class":"POLL","time":"2018-03-02T21:14:54.873Z","active":1,"tpv":[{"class":"TPV","device":"/dev/pts/10","mode":3,"time":"2005-06-09T14:34:53.280Z","ept":0.005,"lat":46.498332203,"lon":7.567403907,"alt":1343.165,"epx":24.829,"epy":25.326,"epv":78.615,"track":10.3788,"speed":0.091,"climb":-0.085,"eps":50.65,"epc":157.23}],"gst":[{"class":"GST","device":"/dev/pts/10","time":"1970-01-01T00:00:00.000Z","rms":0.000,"major":0.000,"minor":0.000,"orient":0.000,"lat":0.000,"lon":0.000,"alt":0.000}],"sky":[{"class":"SKY","device":"/dev/pts/10","time":"2005-06-09T14:34:53.280Z","xdop":1.66,"ydop":1.69,"vdop":3.42,"tdop":3.05,"hdop":2.40,"gdop":5.15,"pdop":4.16,"satellites":[{"PRN":23,"el":6,"az":84,"ss":0,"used":false},{"PRN":28,"el":7,"az":160,"ss":0,"used":false},{"PRN":8,"el":66,"az":189,"ss":45,"used":true},{"PRN":29,"el":13,"az":273,"ss":0,"used":false},{"PRN":10,"el":51,"az":304,"ss":29,"used":true},{"PRN":4,"el":15,"az":199,"ss":36,"used":true},{"PRN":2,"el":34,"az":241,"ss":41,"used":true},{"PRN":27,"el":71,"az":76,"ss":42,"used":true}]}]}
?POLL;
{"class":"POLL","time":"2018-03-02T21:14:58.856Z","active":1,"tpv":[{"class":"TPV","device":"/dev/pts/10","mode":3,"time":"2005-06-09T14:34:53.280Z","ept":0.005,"lat":46.498332203,"lon":7.567403907,"alt":1343.165,"epx":24.829,"epy":25.326,"epv":78.615,"track":10.3788,"speed":0.091,"climb":-0.085,"eps":50.65,"epc":157.23}],"gst":[{"class":"GST","device":"/dev/pts/10","time":"1970-01-01T00:00:00.000Z","rms":0.000,"major":0.000,"minor":0.000,"orient":0.000,"lat":0.000,"lon":0.000,"alt":0.000}],"sky":[{"class":"SKY","device":"/dev/pts/10","time":"2005-06-09T14:34:53.280Z","xdop":1.66,"ydop":1.69,"vdop":3.42,"tdop":3.05,"hdop":2.40,"gdop":5.15,"pdop":4.16,"satellites":[{"PRN":23,"el":6,"az":84,"ss":0,"used":false},{"PRN":28,"el":7,"az":160,"ss":0,"used":false},{"PRN":8,"el":66,"az":189,"ss":45,"used":true},{"PRN":29,"el":13,"az":273,"ss":0,"used":false},{"PRN":10,"el":51,"az":304,"ss":29,"used":true},{"PRN":4,"el":15,"az":199,"ss":36,"used":true},{"PRN":2,"el":34,"az":241,"ss":41,"used":true},{"PRN":27,"el":71,"az":76,"ss":42,"used":true}]}]}
：
{{1}}
答案 2 :(得分：2)
加我的两分钱。
无论出于何种原因，我的覆盆子pi将继续执行一个线程，我必须硬重置pi。
所以我结合了sysnthesizerpatel和我在Dan Mandel的博客here上找到的答案。
我的gps_poller类看起来像这样：
import os
from gps import *
from time import *
import time
import threading
class GpsPoller(threading.Thread):
def __init__(self):
threading.Thread.__init__(self)
self.session = gps(mode=WATCH_ENABLE)
self.current_value = None
self.running = True
def get_current_value(self):
return self.current_value
def run(self):
try:
while self.running:
self.current_value = self.session.next()
except StopIteration:
pass
使用中的代码如下所示：
from gps_poll import *
if __name__ == '__main__':
gpsp = GpsPoller()
try:
gpsp.start()
while True:
os.system('clear')
report = gpsp.get_current_value()
# print report
try:
if report.keys()[0] == 'epx':
print report['lat']
print report['lon']
time.sleep(.5)
except(AttributeError, KeyError):
pass
time.sleep(0.5)
except(KeyboardInterrupt, SystemExit):
print "\nKilling Thread.."
gpsp.running = False
gpsp.join()
print "Done.\nExiting."
答案 3 :(得分：0)
我知道这是一个旧线程，但只是为了让大家理解，您也可以为此使用 pyembedded python 库。
pip install pyembedded
from pyembedded.gps_module.gps import GPS
import time
gps = GPS(port='COM3', baud_rate=9600)
while True:
print(gps.get_lat_long())
time.sleep(1)