[time-nuts] new gps sat prn30 svn64

tom jones epoch_time at yahoo.com
Wed Mar 5 11:19:20 EST 2014

I better explain how to interpet my programs output.
(parser of msg 30 and 41)
My C programming (turbo C for dos) isn't so great.

My program that parses out msg 30 and has wrap around problems in a dos window.
here is the latest data.

prn clk bias     freq drift    delta of      delta of   last    clk bias   time of
#                               2nd value     1st Value update  correction correction

01 2.444682e-06 1.805289e-12   2.008604e-14  2.1064e-10 0624  2.851728e-08 0221
02 4.822064e-04 -6.994180e-13  -2.559389e-14 -1.8880e-11 1247 3.825469e-07 0608
 3 3.338170e-04 -1.446530e-13  1.442900e-14  -3.0300e-12 0243 3.337789e-04 2209
04 5.925871e-06 -7.702133e-13  2.525866e-14  -3.0809e-12 1022 5.002867e-08 0413
05 -3.857823e-04 1.898869e-12  8.883085e-15  5.6970e-11 1313  2.585686e-07 0825

07 3.205445e-04 1.948962e-12   5.041540e-15  3.3130e-11 0524  -3.924453e-07 2140
08 1.216586e-05 -4.228136e-12  9.215718e-15  -1.0147e-10 0629 -2.275090e-07 2302
09 3.099688e-04 5.749916e-124  3.590357e-14  6.3250e-11 0643  1.115118e-08 0333
10 -1.169125e-04 -3.732148e-12 2.896208e-14  -1.3153e-10 1127 1.717084e-08 0635
11 -4.694415e-04 -7.678278e-12 1.505740e-14  -1.8699e-10 0515 -4.693428e-04 0000
12 1.902726e-04 3.823995e-12   -5.947500e-15 1.0672e-10 1229  2.884730e-07 0558
 3 2.347145e-05 -3.571864e-12  3.864378e-14  -3.9759e-10 0338 2.359677e-05 2029
14 1.933203e-04 -3.774090e-12  -1.775706e-14 -7.1700e-11 2109 1.933391e-04 0000
15 -1.665138e-04 -4.073153e-12 3.193192e-15  -1.2275e-10 1313 -1.699136e-08 1053
16 -2.290333e-04 2.271270e-125 1.784684e-14  6.8390e-11 1313  6.469004e-08 1219
17 -7.363667e-05 -4.552428e-12 -2.088173e-14 1.3657e-11 0925  -7.360009e-05 0211
18 3.055097e-04 6.184127e-12   2.091990e-14  1.8347e-10 1313  3.054834e-04 1054
19 -4.427305e-04 -2.738411e-12 2.424970e-14  -3.8340e-11 0351 -1.456134e-08 2302
20 1.671745e-04 3.410605e-12   -1.810003e-12 2.2216e-10 0731  8.188247e-08 0608
21 -3.475306e-04 4.271788e-124 -1.902558e-14 1.2182e-10 1313  -3.475719e-04 0944
22 2.174910e-04 3.388278e-12   1.535512e-14  1.0165e-10 1313  1.195895e-07 1224
23 -1.140106e-06 -5.962289e-12 8.155802e-15  -9.0458e-11 0226 -1.053358e-06 0000
24 -2.442550e-05 -1.579095e-13 -8.446098e-15 -1.1050e-12 1011 -2.441198e-05 0435
25 1.728555e-05 2.677246e-12   -7.713015e-16 8.0317e-11 1313  6.543547e-08 0737
26 1.475605e-04 -1.760653e-11  -1.706621e-14 -5.2820e-10 1313 -7.660844e-08 1040
 7 -1.999184e-05 -5.801356e-13 3.546626e-14  -4.8282e-10 0209 -1.998046e-05 2213
28 3.372821e-04 -3.165018e-13  -4.157156e-14 -1.3070e-11 0758 3.371151e-04 0005
29 5.157496e-04 3.405173e-12   -2.445526e-15 1.0216e-10 1313  5.156916e-04 0800
30 1.999639e-06 3.570054e-12   -3.170207e-16 1.0710e-10 0209  5.961562e-07 0110
31 3.336638e-04 2.788489e-124  -2.070761e-14 3.5211e-10 1140  3.336265e-04 0000
32 -4.751391e-04 9.189593e-12  -9.305317e-14 1.7504e-09 2332  -1.024028e-07 1930

36 41 1782 306881000 03 05 2014
 76135 78583 051 02240 cli04 hed00
 hpe522 vpe104 ck  307542303 dft 1832300
 cder0 dist0 derr0 hder0 sats9 hdop4  dop0

line three (above) is supposed to be prn 03 a wrap around of the second line erased the zero of prn 03.
My previous post I tried to clean up the wrap around effect for prn numbers and typed a 1 instead of zero for prn 4.

09 3.099688e-04 5.749916e-124  3.590357e-14  6.3250e-11 0643  1.115118e-08 0333
line 9 second item (frequency drift) 5.749916e-124 should be interpeted; was -x.xxxxxe-14 in a previous printf statement;
the current drift is actually 5.749916e-12 but hours or even minutes earlier it would have been something like -1.23456xxe-14
The negetive symbol takes up a valuable space in my limited dos window. When a value changes from a negative to positive 

number it frees up a space and the frequency drift value gets shifted left one space leaving a previous digit visiable.
I will clean this up someday. but I find it somewhat usefull.

line prn 25

25 1.728555e-05 2.677246e-12   -7.713015e-16 8.0317e-11 1313  6.543547e-08 0737

The last value (line 25) 0737 utc time of first correction and reception of prn25. 6.543547e-08 0737 = The svn's first daily 

clock bias (which agrees with usno's daily gps report) This last value is the same as the first value only on the first 

initial days prn reception (because it usually contains a major clk bias correction) as received from the gps receiver.

This last value shows large changes (corrections) in the svn clock bias example (actual code not the complete code);

else if ((daily_drift < -.00000001) && (daily_drift > -.001)) {
		    printf("%9le %02d%02d ",daily_drift,hour,minute);

8.0317e-11 1313 (fourth item)  change from previous sample of the first item (clock bias 1.728555e-05) at 1313 hrs utc.

Summary of prn25 (line25);
25 1.728555e-05 2.677246e-12   -7.713015e-16 8.0317e-11 1313  6.543547e-08 0737.

prn 25 was visiable from 0737 to 1313 its clock bias was corrected from what my gps receiver thought the bias should be by 

6.543547e-08 (65.4 ns) either by broadcast message or my gps receiver re-aquireing is signal.

31 3.336638e-04 2.788489e-124  -2.070761e-14 3.5211e-10 1140  3.336265e-04 0000

Interpettation of prn 31;

2.788489e-124 frequency drift was as good as e-14 but currently e-12 (2.0707e-124) this value mostly dopler. Swings as much 

as 6.8xxe-12 to -6.8xxe-12 on satellite pass's directly overhead.

Third value -2.070761e-14 delta of second item (2.788489e-12) from the previous sample which sometimes doesn't change for 90 

I believe this third value (60-90sec delta change of item 2) removes most doplar shift and somehow represents svn clock 

stability somewhat (not programmed for that purpose, may be interpeted lightly as such).

The new satellite prn30 has been consistant (x.xxe-16) on third item values (90second delta freq drift) even though is clk 

bias and frequency drift have changed for the worst. Third item values show prn30 has always had the best stability 


The last value 0000 ; I dont understand this as I dont believe my gps aquired three sats at this time.
three satellites could have gotten clk bias corrections from master control ?
Or message 41 where my program derives utc hour minutes was unavailable ?
it probably was empheris update from master control. I will look at this closer now that I've typed so much about it.

Notice sat 06 has stopped transmissions In the last 24 hours. prn06 was set unuaseable about two weeks ago but had been 

transmitting data.
I think the old prn30 is destined for prn06's slot even though the old prn 30 was unavialable for civilian use for several 

years now prn06 will be unuseable for civilian use...?

Well anyway thats about all I know about my programs intended and unintended information display.

I have all the documentation for sirf receivers, sirf mesages, sirfdemo,etc.  the clock bias and frequency drift is as the 

documentation says "clk bias and frequency drift per satellite" and the source is the gps receiver as well as the broadcast 


I have global sat (sirf-4) bu-353s4 dongle usb gps receiver which produce less radio frequency interference than my holux 

gr-213 sirf III receiver.

The global sat bu-353s4 spits out unwanted data (known bug to other internet users) into my logs. the sirf III didn't have 

this problem.

This is the serial tx messages I sent to the sirf-4 receiver to enable loging and stop unwanted data.

1st mess enables 30second clk status msg 7 
2nd mess enables 30second msg 30 updates (individual satellite data)
3rd mess enables 30sec update of msg 41	 (receiver lat long, tow, heading, speed, utc time date, etc.)
4th mess disable message 225          helps to disable random unwanted data 
5th mess disable mess 255 debug which helps to disable random unknown data spitting into logs

I'm using sirfdemo 3.87 evaluation software that logs satellite data and displays realtime information. It is very old 


More information about the time-nuts mailing list