有没有可以在Python中使用的GPS库？

Question

我在找一个可以处理GPS坐标的Python库。比如说，我有一串坐标：

>>> gps = [
...  (53.25012925, −6.24479338, 349.9, '2011-08-20T09:35:00Z'),
...  (53.25028285, -6.24441800, 359.9, '2011-08-20T09:35:30Z'),
...  (53.25049500, -6.24266032, 395.9, '2011-08-20T09:36:00Z'),
...  # and so on...
... ]
>>>

我想计算平均速度、距离、最高点和其他一些信息。我知道这些计算其实很简单，但我在想有没有现成的代码可以用（我不想重新发明轮子）。

注意：在StackOverflow上有类似的问题（你会推荐哪个Python的GPS库？），但那个是关于GPSD的。我并不在使用任何设备，我只是有一个文本文件里存了GPS坐标。

Answer 1

你可以考虑使用GPSD的一部分数据，而不是从头开始写代码。下面的代码来自GPSD的源代码，它有一个模块可以从GPS数据流中生成路径（然后可以计算路径的长度等等）。

http://code.google.com/p/python-gpsd/source/browse/src/nmea/track.py

class Track(object):

    def __init__(self, recordDelay=10, maxSize=3600, ignoreDuplicates=True, duplicateRange=0.0001):
        """ Constructor

        The default values allow for 10 hours worth of data recorded
        at 10 second intervals.

        recordDelay - Delay between recording data points
        maxSize - Maximum number of points to record
        ignoreDuplicates - Ignore entries that are very similar (ie moved a minimal distance)
        duplicateRange - Varience range within a duplicate is detected (adjust to account for
            subtle gps position drift)
        """
        self.recordDelay = recordDelay
        self.maxSize = maxSize
        self.ignoreDuplicates = ignoreDuplicates
        self.duplicateRange = duplicateRange
        self.positions = []
        self.latest = None

    def append(self, position, heading, timeStamp=None):
        """ Append position and heading information """
        if timeStamp is None: timeStamp = datetime.utcnow()

        self.latest = (timeStamp, position, heading)
        if len(self.positions):
            last = self.positions[0]
        else:
            last = None

        # Make sure we re in range
        if last is None or (timeStamp - last[0]).seconds >= self.recordDelay:
            self.positions.insert(0, self.latest)
            self.latest = None

        # Clear extra data
        if len(self.positions) > self.maxSize: pass

    def clear(self):
        """ Clear all items from track """
        self.positions = []
        self.latest = None

    def __len__(self):
        """ Return the length of the track """
        if self.latest is None: return len(self.positions)
        return len(self.positions) + 1

    def __getslice__(self, i, j):
        return self.positions[i:j]

    def __getitem__(self, i):
        return self.positions[i]

    def get_latest(self):
        if self.latest is None and len(self.positions) > 0:
            return self.positions

    def get_by_time(self, timeRange, now=datetime.utcnow()):
        """ Returns the last n items within the time range """
        result = []
        if self.latest is not None: result.append(self.latest)
        for position in self.positions:
            if (now - position[0]).seconds > timeRange: break
            result.append(position)
        return result

Answer 2

我发现了一个有趣的库，叫做 geopy。这个库可以计算两个GPS点之间的距离（它使用的是大圆距离和文森提距离的方法）。更棒的是，geopy 还可以进行地理编码（也就是说，它可以从地址中获取GPS坐标）。

至于其他功能（比如平均速度、最高点等等），我可以自己动手搞定。