[Python知识库]【Python】RTKLIB POS文件转换至ENU误差并绘图

#!/usr/bin/python
# coding=utf-8
'''
RTKLIB POS文件转换至ENU误差并绘图
Version：1.0
Author:LZ_CUMT
脚本功能：
1：批量读取rtklib解算结果文件（.pos)，并将XYZ或LLH坐标转换为ENU形式
2：转换时选取的坐标基准通过snx文件进行读取，若snx文件中无当前测站或未找到snx文件，以定位结果的均值作为替代
3：转换完成后将ENU输出至csv格式文件保存，通过matplotlib库（需额外安装）绘制ENU定位误差图
'''


import os
import re
import csv
from math import sin,cos,atan,pi,sqrt
import matplotlib.pyplot as plt
# from tkinter import Tk
# from tkinter import filedialog


# 找目录下含该关键词的文件名及其路径
def findfile(filepath,key_word):
    filename = []
    for files in os.listdir(filepath):  # 遍历目录文件名
        if (key_word == 'pos' ):
            if re.match(r'[A-Za-z0-9\.]+\.pos',files):
                filename.append(files)  # 文件名及其路径添加到数组
        elif (key_word == 'snx'):
            if re.match(r'igs[0-9]+\.snx',files):
                filename.append(files)  # 文件名及其路径添加到数组
    return filename  # 返回数组

# 经纬度转化为xyz(参考RTKLIB)
def llh2xyz(lat,lon,h):
    RE_WGS84 = 6378137.0
    FE_WGS84 = 1.0/298.257223563
    lat = lat * pi / 180
    lon = lon * pi / 180
    sinp = sin(lat)
    cosp = cos(lat)
    sinl = sin(lon)
    cosl = cos(lon)
    e2 = FE_WGS84*(2.0-FE_WGS84)
    v = RE_WGS84 / sqrt(1.0 - e2 * sinp * sinp)
    x = (v+h)*cosp*cosl
    y = (v+h)*cosp*sinl
    z = (v*(1.0-e2)+h)*sinp
    return [x,y,z]


# 从pos文件中读取坐标结果，并以xyz坐标形式输出
def readpos(posfilepath) :
    f = open(posfilepath,encoding='gb18030', errors='ignore')
    ln = f.readline()
    while ln:
        if '%  GPST' in ln:
            if 'x-ecef(m)' in ln:
                posmode = 'xyz'
            elif 'latitude(deg)' in ln:
                posmode = 'llh'
            break
        ln = f.readline()
    xyz = []
    while ln:
        ln = f.readline()
        if not ln:
            break
        #content = ln.split(' ')
        if posmode == 'xyz':
            x = float(ln[24:38])
            y = float(ln[39:53])
            z = float(ln[54:69])
            xyz.append([x,y,z])
        elif posmode == 'llh':
            lat = float(ln[24:38])
            lon = float(ln[38:53])
            h = float(ln[53:64])
            xyz.append(llh2xyz(lat,lon,h))
    f.close()
    return xyz


# 根据测站id在snx文件中查找测站精确坐标
def getcrd(siteid,snxfilepath,xyz):
    snxcrd=[]
    if snxfilepath == '':
        print('[WARNING] Not find the snxfile, use the average pos as substitute')
    else:
        f = open(snxfilepath,encoding='gb18030', errors='ignore')
        ln = f.readline()
        while ln:
            ln = f.readline()
            if not ln:
                print('[WARNING] Not find the siteid',siteid,', use the average pos as substitute')
                break
            if ln[14:18]==siteid:
                snxcrd.append(float(ln[47:68]))
                ln = f.readline()
                snxcrd.append(float(ln[47:68]))
                ln = f.readline()
                snxcrd.append(float(ln[47:68]))
                break
        f.close()
    if snxcrd == []:
        x = 0
        y = 0
        z = 0
        for i in range(len(xyz)):
            x = x + xyz[i][0]
            y = y + xyz[i][1]
            z = z + xyz[i][2]
        snxcrd = [x/len(xyz),y/len(xyz),z/len(xyz)]
    else:
        print('[INFO] Find the sitecrd in the snx file')
    print('[INFO] The sitecrd is', snxcrd)
    return snxcrd


# xyz转换为llh（经纬度）
def xyz2llh(ecef):
    aell = 6378137 # WGS - 84 not ITRF
    fell = 1 / 298.257223563
    deg = pi / 180
    u = ecef[0]
    v = ecef[1]
    w = ecef[2]
    esq = 2*fell-fell*fell
    if w == 0:
        lat = 0
    else :
        lat0 = atan(w/(1-esq)*sqrt(u*u+v*v))
        j = 0
        delta = 10^6
        limit = 0.000001/3600*deg
        while delta > limit:
            N = aell / sqrt(1 - esq * sin(lat0)*sin(lat0))
            lat = atan((w / sqrt(u*u + v*v)) * (1 + (esq * N * sin(lat0) / w)))
            delta = abs(lat0 - lat)
            lat0 = lat
            j = j + 1
            if j > 10:
                break
    if u == 0 and v == 0:
        long = 0
    elif u > 0 and v >= 0:
        long = atan(v/u)
    elif u < 0:
        long = pi + atan(v/u)
    elif u > 0 and v < 0:
        long = 2*pi
    elif u == 0 and v > 0:
        long = pi/2
    elif u == 0 and v < 0:
        long = 3*pi/2
    h=(sqrt(u*u+v*v)/cos(lat))-N
    llh=[lat,long,h]
    return llh


# xyz转换至以测站精确坐标为基准的enu坐标
def xyz2enu(xyz,snxcrd):
    enu=[]
    llhcrd = xyz2llh(snxcrd)
    phi = llhcrd[0]
    lam = llhcrd[1]
    sinphi = sin(phi)
    cosphi = cos(phi)
    sinlam = sin(lam)
    coslam = cos(lam)
    for i in range(len(xyz)):
        difxyz=[xyz[i][0]-snxcrd[0],xyz[i][1]-snxcrd[1],xyz[i][2]-snxcrd[2]]
        e = -sinlam*difxyz[0]+coslam*difxyz[1]
        n = -sinphi*coslam*difxyz[0]-sinphi*sinlam*difxyz[1]+cosphi*difxyz[2]
        u =  cosphi*coslam*difxyz[0]+cosphi*sinlam*difxyz[1]+sinphi*difxyz[2]
        enu.append([e,n,u])
    return enu

# 保存enu误差结果为CSV文件
def saveenu(enu,posfilepath):
    f = open(posfilepath[:-4] + '.csv', 'a', newline="")
    csv_write = csv.writer(f)
    for i in range(len(enu)):
        csv_write.writerow([enu[i][0],enu[i][1],enu[i][2]])
    f.close()
    return 0


# 绘制enu误差时间序列图
def plotenu(enu,posfilepath):
    e = []
    n = []
    u = []
    for i in range(len(enu)):
        e.append(enu[i][0])
        n.append(enu[i][1])
        u.append(enu[i][2])
    fig = plt.figure()
    ax = fig.add_subplot(1, 1, 1)
    plt.axis([0, len(enu)+1, -1, 1])
    ax.plot(range(1,len(enu)+1), e)
    ax.plot(range(1,len(enu)+1), n)
    ax.plot(range(1,len(enu)+1), u)
    ax.grid(True, linestyle='--')
    plt.xlabel('[Epoch]')
    plt.ylabel('[Error]')
    plt.legend(['E','N','U'])
    #plt.show()
    plt.savefig(posfilepath[:-4] + '.png', dpi=400)
    plt.close()
    return 0


if __name__ == '__main__':
    # posfilepath = 'D:\\data\\nav\\CEDU.pos'
    # snxfilepath = 'D:\\data\\nav\\CEDU.pos'
    # window = Tk()
    # window.withdraw()
    # filepath = filedialog.askdirectory(title='选择数据所在文件夹')

    # 此处修改文件夹路径，将要处理的pos文件和下载的snx坐标文件统一放于此文件夹下
    filepath = 'D:\\data\\all'
    posfilelist = findfile(filepath,'pos')
    snxfilelist = findfile(filepath,'snx')
    if snxfilelist == []:
        snxfilepath = ''
    else:
        snxfilepath = filepath + '\\' + snxfilelist[0]
        print('[INFO] Find the snxfile :',snxfilelist[0])

    for posfile in posfilelist:
        fileindex = posfilelist.index(posfile) + 1
        posfilepath = filepath + '\\' + posfile
        print('[INFO] Process the '+str(fileindex)+'th posfile :',posfile)
        siteid = posfile[0:4].upper()
        print('[INFO] The siteid is :',siteid)
        xyz = readpos(posfilepath)
        snxcrd = getcrd(siteid,snxfilepath,xyz)
        enu = xyz2enu(xyz,snxcrd)
        saveenu(enu,posfilepath)
        plotenu(enu,posfilepath)
        print('[INFO] Finish the '+str(fileindex)+'th posfile processing successfully')