GPS 下采样
GPS downsampling
我的目标是每 100 米对我的数据进行下采样并获取第一行和最后一行
我的问题是，当我缩减采样时，我得到的行比我应该得到的要少很多，而且我不知道如何得到最后一行。
希望我说得足够清楚，有人能理解
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
您的代码可以进行一些重组以使其更清晰。对于距离小于 100m 的情况，每当看到 EOL 时，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
只要检测到 EOL，您还需要重置 coord1，以确保第一个条目再次显示 0。
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。
解决有关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，那么对您的输入进行采样 "for every 100m" 可能意味着不同的东西，特别是如果运动不是纯线性的。
假设您的输入描述的坐标是通过在沿着半径小于（例如 15 米）的圆移动时定期测量 GPS 坐标而获得的。然后，无论您的输入提供多少数据点，您提出的解决方案的输出都不会超过两条线，因为沿着该曲线的任何两个点的绝对距离都不会超过 100 米。这或许可以解释为什么您在输出中看到的行数少于预期。
如果您打算每隔 100 米 行驶 对输入进行采样，则必须对自最后一个输出采样点以来输入样本之间的所有距离求和，并使用它代替dist。修改 Martin 的重组代码，可以这样来做（为了简洁省略了一些行）：
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
我的目标是每 100 米对我的数据进行下采样并获取第一行和最后一行
我的问题是，当我缩减采样时，我得到的行比我应该得到的要少很多，而且我不知道如何得到最后一行。
希望我说得足够清楚，有人能理解
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
您的代码可以进行一些重组以使其更清晰。对于距离小于 100m 的情况，每当看到 EOL 时，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
只要检测到 EOL，您还需要重置 coord1，以确保第一个条目再次显示 0。
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。
解决有关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，那么对您的输入进行采样 "for every 100m" 可能意味着不同的东西，特别是如果运动不是纯线性的。
假设您的输入描述的坐标是通过在沿着半径小于（例如 15 米）的圆移动时定期测量 GPS 坐标而获得的。然后，无论您的输入提供多少数据点，您提出的解决方案的输出都不会超过两条线，因为沿着该曲线的任何两个点的绝对距离都不会超过 100 米。这或许可以解释为什么您在输出中看到的行数少于预期。
如果您打算每隔 100 米 行驶 对输入进行采样，则必须对自最后一个输出采样点以来输入样本之间的所有距离求和，并使用它代替dist。修改 Martin 的重组代码，可以这样来做（为了简洁省略了一些行）：
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