1

我的目标是每 100m 对我的数据进行下采样并获得第一行和最后一行

我的问题是，当我下采样时，我得到的行数比我应该得到的要少得多，而且我不知道如何得到最后一行。

希望足够清楚，有人可以理解

To make this
Line 20130904_0848.nmea
$GPGGA,111936.00,5849.37538,N,01739.88263,,E,2,09,00.9,00004.43,M,0024.87,M,007,0734*42
$GPGGA,111936.00,5849.37548,N,01739.88240,,E,2,09,00.9,00004.43,M,0024.87,M,007,0734*44
$GPGGA,111936.00,5849.37556,N,01739.88216,,E,2,09,00.9,00004.43,M,0024.87,M,007,0734*48
$GPGGA,111936.00,5849.37569,N,01739.88193,,E,2,09,00.9,00004.43,M,0024.87,M,007,0734*4a
$GPGGA,111936.00,5849.37581,N,01739.88171,,E,2,09,00.9,00004.43,M,0024.87,M,007,0734*40
$GPGGA,111936.00,5849.69118,N,01739.89674,,E,2,09,00.9,00004.43,M,0024.87,M,007,0734*4c
EOL 

Line 20130904_0926.nmea
$GPGGA,111936.00,5849.67569,N,01739.98426,,E,2,09,00.9,00004.43,M,0024.87,M,007,0734*45
$GPGGA,111936.00,5849.67593,N,01739.98453,,E,2,09,00.9,00004.43,M,0024.87,M,007,0734*42
$GPGGA,111936.00,5849.67616,N,01739.98479,,E,2,09,00.9,00004.43,M,0024.87,M,007,0734*44
....

Look like this

Line 20081002-1119.nmea
58.853952   13.309779   0.00
58.853907   13.310688   101.15
58.853858   13.311593   100.72
58.853811   13.312498   100.62
58.853764   13.313402   100.59
58.853752   13.313660   28.70

EOL

Line 20081002-1119.nmea
58.853952   13.309779   0.00
58.853907   13.310688   101.15
58.853858   13.311593   100.72
58.853811   13.312498   100.62
58.853764   13.313402   100.59
...

到目前为止，这是我的代码

from math import sin, cos, sqrt, atan2, radians

coord=[]
coord1=None
def distance(coord1,coord2): #Haversin
    lat1,lon1=coord1
    lat2,lon2=coord2
    dlat = radians(lat2-lat1)
    dlon = radians(lon2-lon1)
    a = sin(dlat/2) * sin(dlat/2)
    + cos(radians(lat1))*cos(radians(lat2))*sin(dlon/2)*sin(dlon/2)
    c = 2 *atan2(sqrt(a),sqrt(1-a))
    s = (6367*c)*1000 #meter
    return s

# with open as data will close itself after reading each line. so you don't need to close it yourself

with open('asko_nav_2013.nmea', 'r') as indata:         #making a indata and outdata, r stands for reading(readcapabilities
    with open('asko_nav_out.txt', 'w') as outdata:      #w stands for write write to a new file(open for writing-you can change things)


        while True:
            line = indata.readline()
            if not line:
                break
            if line.startswith('EOL'):  #if the line starts with EOL(end of line) it writes it in the output
                outdata.writelines("EOL")
                coord1=None
            elif line.startswith('Line'): 
                LineID=line
                outdata.writelines('\n%s' %LineID)
            elif line.startswith('$GPGGA'):  #when the fist line starts with $GPGGA it splits the columns
                data=line.split(",")        #the for loop reads the file line by line



            # Importing only coordinates from asko input file (Row 2 and 4)

                # Converting the coordinates from DDMM.MMMM to DD.DDDDDD
                LAT=(data[2])
                LAT_D=LAT[0:2]               
                LATID=float(LAT_D)

                LAT_M=LAT[2:]
                LATM=float(LAT_M)
                LATIM = float(LATM) / 60.0

                latitude=(LATID + LATIM)                  

                LON=(data[4])
                LON_D=LON[1:3]
                LONGD=float(LON_D)

                LON_M=LON[3:]
                LONM=float(LON_M)
                LONGM = float(LONM) / 60.0

                longitude=(LONGD + LONGM)

                if coord1 is None:

                # The first time through the loop "coord1" is None
                    outdata.writelines('%0.6f\t%0.6f\t%s \n'%(latitude,longitude,0))
                    coord1=(latitude,longitude)
                else:
                    coord2=(latitude,longitude)
                    dist=distance(coord1,coord2)

                    if dist <100:
                        continue
                    outdata.writelines('%0.6f\t%0.6f\t%f\n' % (latitude,longitude,dist))
                    coord1=coord2
4

2 回答 2

0

您的代码可以进行一些重组以使其更清晰。EOL对于距离低于 100m 的情况，您需要添加额外的写入：

from math import sin, cos, sqrt, atan2, radians    

def distance(coord1, coord2): #Haversin
    lat1,lon1=coord1
    lat2,lon2=coord2
    dlat = radians(lat2-lat1)
    dlon = radians(lon2-lon1)
    a = sin(dlat/2) * sin(dlat/2)
    + cos(radians(lat1))*cos(radians(lat2))*sin(dlon/2)*sin(dlon/2)
    c = 2 *atan2(sqrt(a),sqrt(1-a))
    s = (6367*c)*1000 #meter
    return s

def get_coordinates(data):
    # Importing only coordinates from asko input file (Row 2 and 4)
    # Converting the coordinates from DDMM.MMMM to DD.DDDDDD

    LAT = (data[2])
    LAT_D = LAT[0:2]               
    LATID = float(LAT_D)

    LAT_M = LAT[2:]
    LATM = float(LAT_M)
    LATIM = float(LATM) / 60.0

    latitude = (LATID + LATIM)                  

    LON = (data[4])
    LON_D = LON[1:3]
    LONGD = float(LON_D)

    LON_M = LON[3:]
    LONM = float(LON_M)
    LONGM = float(LONM) / 60.0

    longitude = (LONGD + LONGM)

    return (latitude, longitude)


coord1 = None

# with open as data will close itself after reading each line. so you don't need to close it yourself

with open('asko_nav_2013.nmea', 'r') as indata, open('asko_nav_out.txt', 'w') as outdata:
    for line in indata:
        if line.startswith('EOL'):  #if the line starts with EOL(end of line) it writes it in the output
            if dist < 100:
                outdata.write('%0.6f\t%0.6f\t%f\n' % (latitude, longitude, dist))
            outdata.write("\nEOL\n")
            coord1 = None   # Reset the first coordinate
        elif line.startswith('Line'): 
            outdata.write('\n%s' % line)
        elif line.startswith('$GPGGA'):  #when the fist line starts with $GPGGA it splits the columns
            data=line.split(",")        #the for loop reads the file line by line
            latitude, longitude = get_coordinates(data)

            if coord1:
                coord2 = (latitude, longitude)
                dist = distance(coord1, coord2)

                if dist >= 100:
                    outdata.write('%0.6f\t%0.6f\t%f\n' % (latitude, longitude, dist))
                    coord1 = coord2         
            else:
                # The first time through the loop "coord1" is None
                outdata.write('%0.6f\t%0.6f\t0.0 \n' % (latitude, longitude))
                coord1 = (latitude, longitude)

对于您给定的输入，这将生成以下输出文件：

Line 20130904_0848.nmea
58.822923   17.664710   0.0 
58.828186   17.664946   584.888514

EOL

Line 20130904_0926.nmea
58.827928   17.666404   0.0 
58.827936   17.666413   0.870480

EOL

您还需要在检测到coord1时重置EOL以确保0再次显示第一个条目。

很难看出这是否完全解决了问题，因为您的示例数据似乎与您的预期输出不符。

于 2015-11-13T11:05:01.933 回答
0

解决关于结果行少于预期的第二个问题：您提供的有关问题性质和正在处理的输入数据的信息太少。如果您的输入数据是从移动物体行进的轨迹中采样的，特别是如果运动不是纯线性的，那么“每 100m”对输入进行采样可能意味着不同。

想象一下，您的输入描述了通过沿半径小于 15m 的圆移动时定期测量 GPS 坐标获得的坐标。那么无论您的输入提供多少数据点，您提出的解决方案的输出永远不会超过两条线，因为沿着该曲线的任何两个点的绝对距离都不能超过 100m。这可以解释为什么您在输出中看到的行数少于预期。

如果您的意思是每行驶100m 对输入进行采样，则必须对自最后一个采样输出点以来输入样本之间的所有距离求和，并使用它而不是dist. 修改 Martin 重组后的代码，可以这样完成（为简洁起见，省略了一些行）：

coord1 = None
coord_last = None  # holds coordinate of last input sample
dist = 0.0         # total distance travelled since coord1
# [...]
with open('asko_nav_2013.nmea', 'r') as indata, open('asko_nav_out.txt', 'w') as outdata:
    for line in indata:
    # [...]
            if coord1:
                coord2 = (latitude, longitude)
                delta = distance(coord_last, coord2)
                dist += delta
                coord_last = coord2

                if dist >= 100:
                    outdata.write('%0.6f\t%0.6f\t%f\n' % (latitude, longitude, dist))
                    coord1 = coord2
                    dist = 0.0
            else:
                # The first time through the loop "coord1" is None
                outdata.write('%0.6f\t%0.6f\t0.0 \n' % (latitude, longitude))
                coord1 = (latitude, longitude)
                coord_last = coord1
                dist = 0.0
于 2015-11-13T14:43:17.547 回答