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function [gpsEph,iono] = ReadRinexNav(fileName) |
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% [gpsEph,iono] = ReadRinexNav(fileName) |
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% |
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% Read GPS ephemeris and iono data from an ASCII formatted RINEX 2.10 Nav file. |
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% Input: |
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% fileName - string containing name of RINEX formatted navigation data file |
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% Output: |
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% gpsEph: vector of ephemeris data, each element is an ephemeris structure |
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% structure order and orbit variable names follow RINEX 2.1 Table A4 |
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% clock variable names af0, af1, af2 follow IS GPS 200 |
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% gpsEph(i).PRN % SV PRN number |
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% gpsEph(i).Toc % Time of clock (seconds) |
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% gpsEph(i).af0 % SV clock bias (seconds) |
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% gpsEph(i).af1 % SV clock drift (sec/sec) |
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% gpsEph(i).af2 % SV clock drift rate (sec/sec2) |
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% gpsEph(i).IODE % Issue of data, ephemeris |
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% gpsEph(i).Crs % Sine harmonic correction to orbit radius (meters) |
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% gpsEph(i).Delta_n % Mean motion difference from computed value (radians/sec) |
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% gpsEph(i).M0 % Mean anomaly at reference time (radians) |
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% gpsEph(i).Cuc % Cosine harmonic correction to argument of lat (radians) |
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% gpsEph(i).e % Eccentricity (dimensionless) |
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% gpsEph(i).Cus % Sine harmonic correction to argument of latitude (radians) |
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% gpsEph(i).Asqrt % Square root of semi-major axis (meters^1/2) |
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% gpsEph(i).Toe % Reference time of ephemeris (seconds) |
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% gpsEph(i).Cic % Sine harmonic correction to angle of inclination (radians) |
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% gpsEph(i).OMEGA % Longitude of ascending node at weekly epoch (radians) |
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% gpsEph(i).Cis % Sine harmonic correction to angle of inclination (radians) |
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% gpsEph(i).i0 % Inclination angle at reference time (radians) |
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% gpsEph(i).Crc % Cosine harmonic correction to the orbit radius (meters) |
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% gpsEph(i).omega % Argument of perigee (radians) |
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% gpsEph(i).OMEGA_DOT% Rate of right ascension (radians/sec) |
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% gpsEph(i).IDOT % Rate of inclination angle (radians/sec) |
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% gpsEph(i).codeL2 % codes on L2 channel |
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% gpsEph(i).GPS_Week % GPS week (to go with Toe), (NOT Mod 1024) |
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% gpsEph(i).L2Pdata % L2 P data flag |
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% gpsEph(i).accuracy % SV user range accuracy (meters) |
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% gpsEph(i).health % Satellite health |
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% gpsEph(i).TGD % Group delay (seconds) |
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% gpsEph(i).IODC % Issue of Data, Clock |
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% gpsEph(i).ttx % Transmission time of message (seconds) |
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% gpsEph(i).Fit_interval %fit interval (hours), zero if not known |
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% |
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% iono: ionospheric parameter structure |
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% iono.alpha = [alpha0, alpha1, alpha2, alpha3] |
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% iono.beta = [ beta0, beta1, beta2, beta3] |
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% if iono data is not present in the Rinex file, iono is returned empty. |
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fidEph = fopen(fileName); |
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[numEph,numHdrLines] = countEph(fidEph); |
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%Now read from the begining again, looking for iono parameters |
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frewind(fidEph); |
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iono = readIono(fidEph,numHdrLines); |
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%initialize ephemeris structure array: |
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gpsEph = InitializeGpsEph; |
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gpsEph = repmat(gpsEph,1,numEph); |
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%now read each ephemeris into gpsEph(j) |
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%RINEX defines the format in terms of numbers of characters, so that's how we |
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%read it, e.g. "gpsEph(j).PRN = str2num(line(1:2));" and so on |
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for j = 1:numEph |
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line = fgetl(fidEph); |
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gpsEph(j).PRN = str2num(line(1:2)); |
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%NOTE: we use str2num, not str2double, since str2num handles 'D' for exponent |
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%% get Toc (Rinex gives this as UTC time yy,mm,dd,hh,mm,ss) |
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year = str2num(line(3:6)); |
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%convert year to a 4-digit year, this code is good to the year 2080. |
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%From 2080 RINEX 2.1 is ambiguous and shouldnt be used, because is has a |
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%2-digit year, and 100 years will have passed since the GPS Epoch. |
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if year < 80, |
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year = 2000+year; |
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else |
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year = 1900+year; |
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end |
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month = str2num(line(7:9)); |
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day = str2num(line(10:12)); |
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hour = str2num(line(13:15)); |
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minute = str2num(line(16:18)); |
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second = str2num(line(19:22)); |
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%convert Toc to gpsTime |
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gpsTime = Utc2Gps([year,month,day,hour,minute,second]); |
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gpsEph(j).Toc = gpsTime(2); |
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%% get all other parameters |
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gpsEph(j).af0 = str2num(line(23:41)); |
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gpsEph(j).af1 = str2num(line(42:60)); |
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gpsEph(j).af2 = str2num(line(61:79)); |
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line = fgetl(fidEph); |
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gpsEph(j).IODE = str2num(line(4:22)); |
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gpsEph(j).Crs = str2num(line(23:41)); |
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gpsEph(j).Delta_n = str2num(line(42:60)); |
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gpsEph(j).M0 = str2num(line(61:79)); |
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line = fgetl(fidEph); |
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gpsEph(j).Cuc = str2num(line(4:22)); |
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gpsEph(j).e = str2num(line(23:41)); |
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gpsEph(j).Cus = str2num(line(42:60)); |
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gpsEph(j).Asqrt = str2num(line(61:79)); |
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line=fgetl(fidEph); |
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gpsEph(j).Toe = str2num(line(4:22)); |
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gpsEph(j).Cic = str2num(line(23:41)); |
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gpsEph(j).OMEGA = str2num(line(42:60)); |
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gpsEph(j).Cis = str2num(line(61:79)); |
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line = fgetl(fidEph); |
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gpsEph(j).i0 = str2num(line(4:22)); |
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gpsEph(j).Crc = str2num(line(23:41)); |
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gpsEph(j).omega = str2num(line(42:60)); |
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gpsEph(j).OMEGA_DOT = str2num(line(61:79)); |
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line = fgetl(fidEph); |
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gpsEph(j).IDOT = str2num(line(4:22)); |
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gpsEph(j).codeL2 = str2num(line(23:41)); |
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gpsEph(j).GPS_Week = str2num(line(42:60)); |
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gpsEph(j).L2Pdata = str2num(line(61:79)); |
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line = fgetl(fidEph); |
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gpsEph(j).accuracy = str2num(line(4:22)); |
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gpsEph(j).health = str2num(line(23:41)); |
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gpsEph(j).TGD = str2num(line(42:60)); |
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gpsEph(j).IODC = str2num(line(61:79)); |
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line = fgetl(fidEph); |
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gpsEph(j).ttx = str2num(line(4:22)); |
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gpsEph(j).Fit_interval = str2num(line(23:41)); |
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end |
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fclose(fidEph); |
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end %end of function ReadRinexNav |
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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function [numEph,numHdrLines] = countEph(fidEph,fileName) |
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%utility function for ReadRinexNav |
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%Read past the header, and then read to the end, counting ephemerides: |
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numHdrLines = 0; |
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bFoundHeader = false; |
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while ~bFoundHeader %Read past the header |
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numHdrLines = numHdrLines+1; |
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line = fgetl(fidEph); |
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if ~ischar(line), break, end |
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k = strfind(line,'END OF HEADER'); |
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if ~isempty(k), |
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bFoundHeader = true; |
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break |
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end |
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end |
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if ~bFoundHeader |
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error('Error reading file: %s\nExpected RINEX header not found',fileName); |
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end |
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%Now read to the end of the file |
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numEph = -1; |
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while 1 |
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numEph = numEph+1; |
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line = fgetl(fidEph); |
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if line == -1, |
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break; |
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elseif length(line)~=79 |
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%use this opportunity to check line is the right length |
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%because in the rest of ReadRinexNav we depend on line being this length |
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error('Incorrect line length encountered in RINEX file'); |
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end |
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end; |
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%check that we read the expected number of lines: |
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if rem(numEph,8)~=0 |
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error('Number of nav lines in %s should be divisible by 8',fileName); |
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end |
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numEph = numEph/8; %8 lines per ephemeris |
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end %end of function countEph |
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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function iono = readIono(fidEph,numHdrLines) |
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%utility function to read thru the header lines, and find iono parameters |
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iono = []; %return empty if iono not found |
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bIonoAlpha=false; bIonoBeta=false; |
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for i = 1:numHdrLines, |
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line = fgetl(fidEph); |
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% Look for iono parameters, and read them in |
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if ~isempty(strfind(line,'ION ALPHA')) %line contains iono alpha parameters |
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ii = strfind(line,'ION ALPHA'); |
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iono.alpha=str2num(line(1:ii-1)); |
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%If we have 4 parameters then we have the complete iono alpha |
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bIonoAlpha = (length(iono.alpha)==4); |
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end |
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if ~isempty(strfind(line,'ION BETA'))%line contains the iono beta parameters |
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ii = strfind(line,'ION BETA'); |
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iono.beta=str2num(line(1:ii-1)); |
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%If we have 4 parameters then we have the complete iono beta |
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bIonoBeta = (length(iono.beta)==4); |
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end |
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end |
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if ~(bIonoAlpha && bIonoBeta) |
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%if we didn't get both alpha and beta iono correctly, then return empty iono |
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iono=[]; |
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end |
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end %end of function readIono |
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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function gpsEph = InitializeGpsEph |
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%utility function to initialize the ephemeris structure |
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gpsEph.PRN = 0; |
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gpsEph.Toc = 0; |
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gpsEph.af0 = 0; |
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gpsEph.af1 = 0; |
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gpsEph.af2 = 0; |
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gpsEph.IODE = 0; |
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gpsEph.Crs = 0; |
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gpsEph.Delta_n = 0; |
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gpsEph.M0 = 0; |
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gpsEph.Cuc = 0; |
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gpsEph.e = 0; |
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gpsEph.Cus = 0; |
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gpsEph.Asqrt = 0; |
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gpsEph.Toe = 0; |
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gpsEph.Cic = 0; |
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gpsEph.OMEGA = 0; |
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gpsEph.Cis = 0; |
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gpsEph.i0 = 0; |
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gpsEph.Crc = 0; |
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gpsEph.omega = 0; |
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gpsEph.OMEGA_DOT = 0; |
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gpsEph.IDOT = 0; |
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gpsEph.codeL2 = 0; |
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gpsEph.GPS_Week = 0; |
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gpsEph.L2Pdata = 0; |
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gpsEph.accuracy = 0; |
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gpsEph.health = 0; |
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gpsEph.TGD = 0; |
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gpsEph.IODC = 0; |
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gpsEph.ttx = 0; |
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gpsEph.Fit_interval= 0; |
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end %end of function InitializeEph |
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%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% |
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% Copyright 2016 Google Inc. |
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% |
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% Licensed under the Apache License, Version 2.0 (the "License"); |
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% you may not use this file except in compliance with the License. |
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% You may obtain a copy of the License at |
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% |
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% http://www.apache.org/licenses/LICENSE-2.0 |
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% |
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% Unless required by applicable law or agreed to in writing, software |
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% distributed under the License is distributed on an "AS IS" BASIS, |
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% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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% See the License for the specific language governing permissions and |
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% limitations under the License.
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