119 lines
3.1 KiB
Matlab
119 lines
3.1 KiB
Matlab
function [time, dt, sats, eof] = fepoch_0(fid)
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% FEPOCH_0 Finds the next epoch in an opened RINEX file with
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% identification fid. From the epoch line is produced
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% time (in seconds of week), number of sv.s, and a mark
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% about end of file. Only observations with epoch flag 0
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% are delt with.
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%Kai Borre 09-14-96; revised 03-22-97; revised Sept 4, 2001
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%Copyright (c) by Kai Borre
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%$Revision: 1.0 $ $Date: 1997/09/22 $
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%fide = fopen(fid,'rt');
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% 该函数只返回ｏ文件中一个历元的以下参数：
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% time：周内秒
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% dt：接收机钟差（该参数为可选项，不一定所有的o文件中都有）
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% sats：当前历元所观测到的卫星
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% eof：是否到文件末尾
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global sat_index;
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time = 0;
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dt = 0;
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sats = [];
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NoSv = 0;
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eof = 0;
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%循环读取o文件的每一行
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while 1
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lin = fgets(fid); % earlier fgetl 先读一行
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if (feof(fid) == 1); % 若到文件末尾，则结束
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eof = 1;
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break
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end;
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% 跳过空行
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if length(lin) <= 1
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continue;
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end
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% answer = findstr(lin,'COMMENT'); % 判断该行中是否有字符串“COMMENT”
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%
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% if ~isempty(answer); % 若有“COMMENT“，则继续读下一行
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% lin = fgetl(fid);
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% end;
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% 如果该行数据第29个字符不为0（0代表改历元正常），
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% 或者总长度只有29（也就是没有后面的卫星PRN数据），
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% 则结束。
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% if ((strcmp(lin(29),'0') == 0) & (size(deblank(lin),2) == 29))
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% eof = 1;
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% break
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% end; % We only want type 0 data
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% 如果该行第二个字符是1，或者第29个字符是0，则说明
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% 这一行是某一历元的开始行，接下来就可以从该行中提取时间、PRN等参数
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if ((strcmp(lin(2),'1') == 1) & (strcmp(lin(29),'0') == 1))
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ll = length(lin)-2;
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if ll > 60, ll = 60; end;
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linp = lin(1:ll);
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%fprintf('%60s\n',linp);
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%使用strtok函数获得间隔符前面的字符串，
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% 首先是获得当前时间
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[nian, lin] = strtok(lin);
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% year;
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[month, lin] = strtok(lin);
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% month;
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[day, lin] = strtok(lin);
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% day;
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[hour, lin] = strtok(lin);
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% hour
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[minute, lin] = strtok(lin);
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% minute
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[second, lin] = strtok(lin);
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% second
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[OK_flag, lin] = strtok(lin);
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% OK_flag就是第29个字符，如果是0，则该历元正常
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%将时间转成数值型，然后再计算出GPS周和周内秒
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h = str2num(hour)+str2num(minute)/60+str2num(second)/3600;
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jd = julday(str2num(nian)+2000, str2num(month), str2num(day), h);
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[week, sec_of_week] = gps_time(jd);
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time = sec_of_week;
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%获得该历元卫星数
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[NoSv, lin] = strtok(lin,'G');
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%储存该历元每颗卫星的PRN
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for k = 1:str2num(NoSv)
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[sat, lin] = strtok(lin,'G');
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prn(k) = str2num(sat);
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end
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% prn是1行NoSv列的矩阵，sats是其转置
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sats = prn(:);
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% 接收及钟差，有的o文件中没有该参数
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dT = strtok(lin);
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if isempty(dT) == 0 %如果dT不为0，则将其记录
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dt = str2num(dT);
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end
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break % 跳出while循环
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end
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end;
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% datee=[str2num(nian) str2num(month) str2num(day) str2num(hour) str2num(minute) str2num(second)];
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%%%%%%%% end fepoch_0.m %%%%%%%%%
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