yumaread
Description
Examples
Read GPS Navigation Message Data from YUMA Almanac File
Download the YUMA almanac file from the NAVCEN website and parse it. Specify the date for which to download the file.
d = datetime("today") - 2;
Create the URL.
baseURL = "https://www.navcen.uscg.gov/sites/default/files/gps/almanac/"; almanacType = "/yuma/"; almanacExtension = ".alm"; url = baseURL + d.Year + almanacType + num2str(day(d,"dayofyear"),'%03d') + ... almanacExtension;
Specify a filename for the saved almanac file.
filename = "yumaAlmanac" + "_" + d.Year + "-" + ... d.Month + "-" + d.Day + ".alm";
Save the file.
websave(filename,url);
Get the orbital parameters from the downloaded YUMA almanac file.
data = yumaread(filename)
data=31×13 timetable
Time PRN Health Eccentricity TimeOfApplicability OrbitalInclination RateOfRightAscen SQRTA RightAscenAtWeek ArgumentOfPerigee MeanAnom Af0 Af1 Week
____________________ ___ ______ ____________ ___________________ __________________ ________________ ______ ________________ _________________ _________ ___________ ___________ ____
27-Jan-2023 19:56:30 1 0 0.012259 5.0381e+05 0.98919 -7.6575e-09 5153.6 -1.7636 0.93699 -1.3324 0.00021935 -3.638e-12 2246
27-Jan-2023 19:56:30 2 0 0.020082 5.0381e+05 0.96693 -7.8289e-09 5153.6 -1.86 -1.3346 -2.3153 -0.00062466 3.638e-12 2246
27-Jan-2023 19:56:30 3 0 0.004446 5.0381e+05 0.9773 -7.8746e-09 5153.7 -0.73153 1.0233 -2.4793 -0.00036907 3.638e-12 2246
27-Jan-2023 19:56:30 4 0 0.0022964 5.0381e+05 0.96264 -7.8975e-09 5153.7 0.34944 -3.0639 0.47758 -4.0054e-05 7.276e-12 2246
27-Jan-2023 19:56:30 5 0 0.0057855 5.0381e+05 0.9643 -8.0232e-09 5153.5 -0.77652 1.1341 1.2373 -0.00011349 0 2246
27-Jan-2023 19:56:30 6 0 0.0028877 5.0381e+05 0.98846 -7.6346e-09 5153.6 -1.7719 -0.86284 -1.0726 0.00056458 3.638e-12 2246
27-Jan-2023 19:56:30 7 0 0.016655 5.0381e+05 0.95017 -7.8746e-09 5153.5 1.3653 -2.2286 -1.9321 0.00025177 -7.276e-12 2246
27-Jan-2023 19:56:30 8 0 0.0082297 5.0381e+05 0.96065 -8.0803e-09 5153.6 -2.8518 0.20048 0.91139 -0.00010586 -3.638e-12 2246
27-Jan-2023 19:56:30 9 0 0.0025482 5.0381e+05 0.95586 -7.9889e-09 5153.6 0.29373 1.9652 1.2322 -0.00022888 7.276e-12 2246
27-Jan-2023 19:56:30 10 0 0.0084252 5.0381e+05 0.97706 -7.8746e-09 5153.6 -0.73421 -2.4529 2.8739 -2.1935e-05 0 2246
27-Jan-2023 19:56:30 11 0 0.00078106 5.0381e+05 0.96453 -7.8746e-09 5153.7 -1.7278 -2.6895 0.14565 -8.8692e-05 -1.0914e-11 2246
27-Jan-2023 19:56:30 12 0 0.0088811 5.0381e+05 0.96648 -8.0003e-09 5153.6 2.48 1.3307 -2.7255 -0.00033283 -3.638e-12 2246
27-Jan-2023 19:56:30 13 0 0.0067534 5.0381e+05 0.96972 -7.8175e-09 5153.6 0.45204 0.94145 0.42546 0.00046635 7.276e-12 2246
27-Jan-2023 19:56:30 14 0 0.002604 5.0381e+05 0.94981 -8.1489e-09 5153.6 2.4432 -3.0813 -2.6751 -4.0054e-05 7.276e-12 2246
27-Jan-2023 19:56:30 15 0 0.014733 5.0381e+05 0.93207 -8.2861e-09 5153.6 0.17855 1.1759 -0.076497 8.5831e-06 3.638e-12 2246
27-Jan-2023 19:56:30 16 0 0.013348 5.0381e+05 0.96625 -8.0003e-09 5153.7 2.4984 0.75825 1.7264 -0.00052261 0 2246
⋮
View Satellite Positions Visible from Receiver Position Using YUMA Almanac File
Read GPS and QZSS navigation message data from a YUMA almanac file.
gpsQzssData = yumaread("qg2022309.alm");
Get the satellite positions, velocities, and IDs at the specified time.
t = datetime(2022,11,10,8,12,00);
[satPos,satVel,satID] = gnssconstellation(t,gpsQzssData,GNSSFileType="YUMA");
Specify a GNSS receiver position in geodetic coordinates (latitude, longitude, and altitude).
recPos = [35.67 139.73 50]; % Tokyo
Get the azimuth and elevation look angles of the satellite positions for the specified receiver position. The isVis
output indicates which satellites are visible. Find the total number of visible satellites by using nnz
.
[az,el,isVis] = lookangles(recPos,satPos);
fprintf('%d satellites visible at %s.\n',nnz(isVis),t);
12 satellites visible at 10-Nov-2022 08:12:00.
Specify the PRN as the label for each point. Specify the categorical groups.
prn = gpsQzssData.PRN; GPSPrn = (prn <= 32); group = categorical(GPSPrn,[true false],["GPS" "QZSS"]);
Visualize the visible satellites. Show the legend.
skyplot(az(isVis),el(isVis),satID(isVis),GroupData=group(isVis)) legend("GPS","QZSS")
Extract GPS and QZSS Data from YUMA Almanac File
Read a YUMA almanac file containing GPS and QZSS data, downloaded from the QZSS website.
filenameQG = "qg2022309.alm";
dataQG = yumaread(filenameQG)
dataQG=35×13 timetable
Time PRN Health Eccentricity TimeOfApplicability OrbitalInclination RateOfRightAscen SQRTA RightAscenAtWeek ArgumentOfPerigee MeanAnom Af0 Af1 Week
____________________ ___ ______ ____________ ___________________ __________________ ________________ ______ ________________ _________________ ________ ___________ __________ ____
08-Nov-2022 16:50:54 1 0 0.01204 2.3347e+05 0.98919 -7.5089e-09 5153.6 -0.38418 0.94107 0.45277 0.00025463 -7.276e-12 2235
08-Nov-2022 16:50:54 2 0 0.02012 2.3347e+05 0.96699 -7.7603e-09 5154.9 -0.47885 -1.3867 -0.44223 -0.00063896 3.638e-12 2235
08-Nov-2022 16:50:54 3 0 0.0044513 2.3347e+05 0.97615 -7.5889e-09 5153.7 0.64757 1.0521 -0.66094 -0.00037193 -3.638e-12 2235
08-Nov-2022 16:50:54 4 0 0.0021377 2.3347e+05 0.96147 -8.0232e-09 5153.7 1.7292 -3.1181 2.3566 -8.9645e-05 7.276e-12 2235
08-Nov-2022 16:50:54 5 0 0.0059276 2.3347e+05 0.9632 -7.726e-09 5153.5 0.60365 1.1404 2.9734 -0.00010395 0 2235
08-Nov-2022 16:50:54 6 0 0.0026011 2.3347e+05 0.98847 -7.5317e-09 5153.5 -0.39246 -0.91841 0.726 0.00051308 1.0914e-11 2235
08-Nov-2022 16:50:54 7 0 0.016459 2.3347e+05 0.95087 -7.7375e-09 5153.6 2.7459 -2.2384 -0.16947 0.00028992 -3.638e-12 2235
08-Nov-2022 16:50:54 8 0 0.0077338 2.3347e+05 0.96113 -8.3432e-09 5153.6 -1.4706 0.16515 2.7185 -9.2506e-05 -3.638e-12 2235
08-Nov-2022 16:50:54 9 0 0.0026331 2.3347e+05 0.95461 -8.1032e-09 5153.7 1.6741 1.9245 3.0836 -0.0002718 7.276e-12 2235
08-Nov-2022 16:50:54 10 0 0.0081372 2.3347e+05 0.97593 -7.5546e-09 5153.6 0.64487 -2.5026 -1.554 -1.1444e-05 0 2235
08-Nov-2022 16:50:54 11 0 0.00080109 2.3347e+05 0.9645 -7.726e-09 5153.6 -0.34663 -2.9148 2.172 -3.7193e-05 -7.276e-12 2235
08-Nov-2022 16:50:54 12 0 0.0085993 2.3347e+05 0.96761 -7.886e-09 5153.7 -2.4237 1.3193 -0.90595 -0.00030231 -3.638e-12 2235
08-Nov-2022 16:50:54 13 0 0.0066509 2.3347e+05 0.96872 -7.9432e-09 5153.6 1.8313 0.95082 2.2082 0.00042057 7.276e-12 2235
08-Nov-2022 16:50:54 14 0 0.0023918 2.3347e+05 0.95102 -8.0003e-09 5153.6 -2.4592 -3.0426 -0.9278 -8.5831e-05 3.638e-12 2235
08-Nov-2022 16:50:54 15 0 0.014719 2.3347e+05 0.9307 -8.3661e-09 5153.6 1.5609 1.157 1.7184 -1.4305e-05 3.638e-12 2235
08-Nov-2022 16:50:54 16 0 0.012957 2.3347e+05 0.9674 -7.9089e-09 5153.7 -2.4053 0.73788 -2.6905 -0.00052643 0 2235
⋮
Extract GPS data from the timetable based on valid GPS PRNs between 1
and 32
.
GPSdata = dataQG((dataQG.PRN >= 1 & dataQG.PRN <= 32),:)
GPSdata=31×13 timetable
Time PRN Health Eccentricity TimeOfApplicability OrbitalInclination RateOfRightAscen SQRTA RightAscenAtWeek ArgumentOfPerigee MeanAnom Af0 Af1 Week
____________________ ___ ______ ____________ ___________________ __________________ ________________ ______ ________________ _________________ ________ ___________ __________ ____
08-Nov-2022 16:50:54 1 0 0.01204 2.3347e+05 0.98919 -7.5089e-09 5153.6 -0.38418 0.94107 0.45277 0.00025463 -7.276e-12 2235
08-Nov-2022 16:50:54 2 0 0.02012 2.3347e+05 0.96699 -7.7603e-09 5154.9 -0.47885 -1.3867 -0.44223 -0.00063896 3.638e-12 2235
08-Nov-2022 16:50:54 3 0 0.0044513 2.3347e+05 0.97615 -7.5889e-09 5153.7 0.64757 1.0521 -0.66094 -0.00037193 -3.638e-12 2235
08-Nov-2022 16:50:54 4 0 0.0021377 2.3347e+05 0.96147 -8.0232e-09 5153.7 1.7292 -3.1181 2.3566 -8.9645e-05 7.276e-12 2235
08-Nov-2022 16:50:54 5 0 0.0059276 2.3347e+05 0.9632 -7.726e-09 5153.5 0.60365 1.1404 2.9734 -0.00010395 0 2235
08-Nov-2022 16:50:54 6 0 0.0026011 2.3347e+05 0.98847 -7.5317e-09 5153.5 -0.39246 -0.91841 0.726 0.00051308 1.0914e-11 2235
08-Nov-2022 16:50:54 7 0 0.016459 2.3347e+05 0.95087 -7.7375e-09 5153.6 2.7459 -2.2384 -0.16947 0.00028992 -3.638e-12 2235
08-Nov-2022 16:50:54 8 0 0.0077338 2.3347e+05 0.96113 -8.3432e-09 5153.6 -1.4706 0.16515 2.7185 -9.2506e-05 -3.638e-12 2235
08-Nov-2022 16:50:54 9 0 0.0026331 2.3347e+05 0.95461 -8.1032e-09 5153.7 1.6741 1.9245 3.0836 -0.0002718 7.276e-12 2235
08-Nov-2022 16:50:54 10 0 0.0081372 2.3347e+05 0.97593 -7.5546e-09 5153.6 0.64487 -2.5026 -1.554 -1.1444e-05 0 2235
08-Nov-2022 16:50:54 11 0 0.00080109 2.3347e+05 0.9645 -7.726e-09 5153.6 -0.34663 -2.9148 2.172 -3.7193e-05 -7.276e-12 2235
08-Nov-2022 16:50:54 12 0 0.0085993 2.3347e+05 0.96761 -7.886e-09 5153.7 -2.4237 1.3193 -0.90595 -0.00030231 -3.638e-12 2235
08-Nov-2022 16:50:54 13 0 0.0066509 2.3347e+05 0.96872 -7.9432e-09 5153.6 1.8313 0.95082 2.2082 0.00042057 7.276e-12 2235
08-Nov-2022 16:50:54 14 0 0.0023918 2.3347e+05 0.95102 -8.0003e-09 5153.6 -2.4592 -3.0426 -0.9278 -8.5831e-05 3.638e-12 2235
08-Nov-2022 16:50:54 15 0 0.014719 2.3347e+05 0.9307 -8.3661e-09 5153.6 1.5609 1.157 1.7184 -1.4305e-05 3.638e-12 2235
08-Nov-2022 16:50:54 16 0 0.012957 2.3347e+05 0.9674 -7.9089e-09 5153.7 -2.4053 0.73788 -2.6905 -0.00052643 0 2235
⋮
Extract QZSS data from the timetable based on valid QZSS PRNs between 193
and 202
.
QZSSData = dataQG((dataQG.PRN >= 193 & dataQG.PRN <= 202),:)
QZSSData=4×13 timetable
Time PRN Health Eccentricity TimeOfApplicability OrbitalInclination RateOfRightAscen SQRTA RightAscenAtWeek ArgumentOfPerigee MeanAnom Af0 Af1 Week
____________________ ___ ______ ____________ ___________________ __________________ ________________ ______ ________________ _________________ ________ ___________ ___ ____
08-Nov-2022 08:53:02 194 0 0.076374 2.048e+05 0.72544 -2.343e-09 6492.9 -2.4966 -1.5847 2.5734 0 0 2235
08-Nov-2022 08:53:02 195 0 0.074928 2.048e+05 0.71092 -2.3772e-09 6493.5 -0.78221 -1.5662 0.8499 -3.8147e-06 0 2235
08-Nov-2022 08:53:02 196 0 0.074762 2.048e+05 0.60598 -3.383e-09 6493.2 0.94933 -1.559 -0.93973 0.00011253 0 2235
08-Nov-2022 08:53:02 199 0 0.00022411 2.048e+05 0.0011924 1.0286e-09 6493.4 3.1171 0.38448 1.0834 0 0 2235
Plot Trajectories of Satellites over Time from YUMA Almanac File
Read GPS navigation message data from a YUMA almanac file.
gpsData = yumaread("yumaAlmanac_2022-9-27.alm");
Use the initial GPS timestamp from the almanac data to determine the absolute GPS times for each 60 second time step across 12 hours.
startTime = gpsData.Time(1); numHours = 12; secondsPerHour = 3600; dt = 60; timeElapsed = 0:dt:(numHours*secondsPerHour); t = startTime + seconds(timeElapsed);
Specify a GNSS receiver position in geodetic coordinates (latitude, longitude, and altitude).
recPos = [42 -71 50]; % Natick, MA
Get the azimuth and elevation look angles for the positions of all satellites for the specified receiver position.
numSats = numel(gpsData.PRN); % Number of satellites [allAz,allEl] = deal(NaN(numel(t),numSats)); for i = 1:numel(t) [satPos,~,satID] = gnssconstellation(t(i),gpsData,GNSSFileType="YUMA"); [az,el,vis] = lookangles(recPos,satPos); allAz(i,:) = az; allEl(i,:) = el; end
Mark all satellites below the horizon as NaN
for no visibility.
allEl(allEl < 0) = NaN;
Visualize the trajectories of the satellites.
figure skyplot(allAz,allEl,satID)
Animate the trajectories of the satellites.
figure sp = skyplot(allAz(1,:),allEl(1,:),satID); for i = 1:size(allAz,1) set(sp,AzimuthData=allAz(1:i,:),ElevationData=allEl(1:i,:)) drawnow end
Input Arguments
filename
— YUMA almanac filename
string scalar | character vector
YUMA almanac filename, specified as a string scalar or character vector. You can specify a relative or an absolute path, but if you specify only the filename itself, the function saves the file in the current working directory. The filename can also include a file extension.
Example: "yumaAlmanac_2022-4-20.alm"
Example: "mydir/yumaAlmanac_2022-4-20.alm"
Example: "C:/mydir/yumaAlmanac_2022-4-20.alm"
Data Types: char
| string
refdate
— Reference date
"06-Jan-1980"
| "21-Aug-1999"
| "06-Apr-2019"
Reference date, specified as one of these valid datetime
strings that coincide with the GPS week number rollover
dates:
"06-Jan-1980"
"21-Aug-1999"
"06-Apr-2019"
These dates occur every 1024 weeks, starting from January 6, 1980 at 00:00 (UTC).
The default value is a datetime
string that coincides with the most
recent GPS week number rollover date before the current day.
Example: GPSWeekEpoch="21-Aug-1999"
Data Types: char
| string
Output Arguments
data
— Parameters of each satellite
timetable
Parameters of each satellite, returned as a timetable
with a row for each record and a column for each parameter in that
record.
Parameter | Data Type | Description |
---|---|---|
Time | datetime | GPS Time, calculated using |
PRN | double | Satellite pseudorandom noise number. |
Health | double | Satellite vehicle health data code. |
Eccentricity | double | Eccentricity of the orbit. |
TimeOfApplicability | double | Number of seconds since beginning of GPS week number. |
OrbitalInclination | double | Inclination angle at reference time, in radians. |
RateOfRightAscen | double | Rate of change in measurement of angle of right ascension, in radians per second. |
SQRTA | double | Square root of semimajor axis, in meters1/2. |
RightAscenAtWeek | double | Geographic longitude of orbital plane at weekly epoch, in radians. |
ArgumentOfPerigee | double | Angle from equator to perigee, in radians. |
MeanAnom | double | Angle from position of satellite in its orbit relative to perigee, in radians. |
Af0 | double | Satellite almanac zeroth-order clock correction term, in seconds. |
Af1 | double | Satellite almanac first order clock correction term, in seconds per second. |
Week | double | GPS week number, continuous, not
|
Tips
To download YUMA almanac files from the NAVCEN website for the current date, you must specify a date two days before the current date because the GPS time of applicability is approximately 70 hours later than the transmission time of the almanac data set. See the Read GPS Navigation Message Data from YUMA Almanac File example for more details.
References
[1] Science Applications International Corporation. NAVSTAR GPS Space Segment/Navigation User Interfaces. IS-GPS-200M. Los Angeles, CA: United States Space Force Space Systems Command, approved May 21, 2021. https://www.navcen.uscg.gov/sites/default/files/pdf/gps/IS_GPS_200M.pdf.
[2] Science Applications International Corporation. NAVSTAR GPS Space Segment/Navigation User Interfaces. ICD-GPS-240D. Los Angeles, CA: United States Space Force Space Systems Command, approved May 21, 2021. https://www.navcen.uscg.gov/sites/default/files/pdf/gps/ICD_GPS_240D.pdf.
[3] United States Coast Guard. "GPS Almanacs, NANUs, and OPS Advisories Archives." US Coast Guard Navigation Center. Accessed May 6, 2022. https://www.navcen.uscg.gov/archives.
[4] Quasi-Zenith Satellite System(QZSS). "Satellite Positioning, Navigation and Timing Service." Accessed September 20, 2022. https://qzss.go.jp/en/technical/download/pdf/ps-is-qzss/is-qzss-pnt-004.pdf.
[5] QZSS almanac archives, Quasi-Zenith Satellite System(QZSS). "QZSS (Quasi-Zenith Satellite System) - Cabinet Office (Japan)" Accessed September 20, 2022. https://sys.qzss.go.jp/dod/en/archives/pnt.html.
Version History
Introduced in R2023a
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