Load and plot Galileo satellite phase centres from an Antex file

load_plot_antex.py

import numpy as np
from matplotlib import pyplot as plt
import time
antexfilename='C:\\Users\\tabbott\\Desktop\\antex\\ngs14.atx'


def readuntil(atx,tofind):
    comment=''
    while comment!=tofind:
        try:
            lin=atx.readline()
            if len(lin)==0:
                print 'end of file '
                break
        except:
            print 'other error ',traceback.print_exc()
            time.sleep(2)
            exit(0)
        comment=lin[60:-1].strip()
    return comment,lin[:60]


atx=open(antexfilename,'r')
print 'opened file',atx.name

numstore=[]
neustore=np.empty((0,3))
maxplots=5
galcount=0
lin=' '
while (len(lin)>0):
    comment,lin=readuntil(atx,'START OF ANTENNA')
    
    if len(lin)>0:
        comment,lin=readuntil(atx,'TYPE / SERIAL NO')
        antname=lin[:20].strip()
        antnum=lin[20:40].strip()
        antnumlong=lin[20:60].strip()
        if antname[:7]=='GALILEO':
            galcount+=1
            comment,lin=readuntil(atx,'DAZI')
            dazi=float(lin[:20].strip())
            comment,lin=readuntil(atx,'ZEN1 / ZEN2 / DZEN')
            zen=np.fromstring(lin[:60],sep=' ')
            comment,lin=readuntil(atx,'# OF FREQUENCIES')
            nfreqs=int(lin[:20])
            print 'Line ',atx.tell(),antname,antnumlong
            if galcount<maxplots:
                fig,ax=plt.subplots(figsize=(8,6))
            for f in range(nfreqs):
                comment,lin=readuntil(atx,'START OF FREQUENCY')
                freqname=lin[3:20].strip()
                comment,lin=readuntil(atx,'NORTH / EAST / UP')
                neu=np.fromstring(lin[:60],sep=' ')
                if True: #freqname=='E01':
                    print '  freq',freqname,'has NEU',neu
                    numstore.append(antnum)
                    neustore = np.vstack((neustore,neu))
                if galcount<maxplots:
                    lin=atx.readline()
                    if lin[3:8]=='NOAZI':
                        noazi=np.fromstring(lin[8:],sep=' ')
                        theta=np.linspace(zen[0],zen[1],num=int((zen[1]-zen[0])/zen[2])+1)
                        ax.plot(theta,noazi,label=freqname)
            if galcount<maxplots:
                ax.legend(loc=3)
                plt.xlabel('nadir angle, degrees (12.5 deg is the limb of the earth')
                plt.ylabel('phase centre delta, mm')
                plt.xlim([0,12.5]);  plt.ylim([-2,1])
                plt.title('%s - %s.\nPhase centre from CoM is N %.1f E %.1f U %.1f mm\n Deviation from phase centre, by frequency is as follows:'
                          % (antname,antnum,neu[0],neu[1],neu[2]))
                ax.grid()
                plt.show()
                
        comment,lin=readuntil(atx,'END OF ANTENNA')

atx.close()