NTPsec

Pi5/UputronicsV2

Report generated: Sun May 24 15:53:27 2020 UTC
Start Time: Sun May 17 15:53:02 2020 UTC
End Time: Sun May 24 15:53:02 2020 UTC
Report Period: 7.0 days

Daily stats   Weekly stats   24 Hour scatter plots ( 1, 2, 3 )

Local Clock Time/Frequency Offsets

local offset plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Time Offset -3.984 -2.219 -1.572 -0.260 3.147 5.126 9.680 4.719 7.345 1.420 -0.005 µs -2.131 7.87
Local Clock Frequency Offset -6.387 -6.340 -6.273 -5.980 -5.761 -5.684 -5.674 0.512 0.656 0.153 -5.995 ppm -6.48e+04 2.606e+06

The time and frequency offsets between the ntpd calculated time and the local system clock. Showing frequency offset (red, in parts per million, scale on right) and the time offset (blue, in μs, scale on left). Quick changes in time offset will lead to larger frequency offsets.

These are fields 3 (time) and 4 (frequency) from the loopstats log file.



Local RMS Time Jitter

local jitter plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local RMS Time Jitter 66.000 96.000 111.000 158.000 334.000 538.000 899.000 223.000 442.000 79.425 177.223 ns 8.905 45.65

The RMS Jitter of the local clock offset. In other words, how fast the local clock offset is changing.

Lower is better. An ideal system would be a horizontal line at 0μs.

RMS jitter is field 5 in the loopstats log file.



Local RMS Frequency Jitter

local stability plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local RMS Frequency Jitter 0.020 0.033 0.044 0.183 0.784 1.253 1.911 0.740 1.220 0.242 0.248 ppb 2.824 12.69

The RMS Frequency Jitter (aka wander) of the local clock's frequency. In other words, how fast the local clock changes frequency.

Lower is better. An ideal clock would be a horizontal line at 0ppm.

RMS Frequency Jitter is field 6 in the loopstats log file.



Local Clock Time Offset Histogram

local offset histogram plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Offset -3.984 -2.219 -1.572 -0.260 3.147 5.126 9.680 4.719 7.345 1.420 -0.005 µs -2.131 7.87

The clock offsets of the local clock as a histogram.

The Local Clock Offset is field 3 from the loopstats log file.



Local Temperatures

local temps plot

Local temperatures. These will be site-specific depending upon what temperature sensors you collect data from. Temperature changes affect the local clock crystal frequency and stability. The math of how temperature changes frequency is complex, and also depends on crystal aging. So there is no easy way to correct for it in software. This is the single most important component of frequency drift.

The Local Temperatures are from field 3 from the tempstats log file.



Local Frequency/Temp

local freq temps plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Frequency Offset -6.387 -6.340 -6.273 -5.980 -5.761 -5.684 -5.674 0.512 0.656 0.153 -5.995 ppm -6.48e+04 2.606e+06
Temp ZONE0 40.780 41.856 42.932 45.084 47.774 48.850 49.388 4.842 6.994 1.587 45.299 °C

The frequency offsets and temperatures. Showing frequency offset (red, in parts per million, scale on right) and the temperatures.

These are field 4 (frequency) from the loopstats log file, and field 3 from the tempstats log file.



Local GPS

local gps plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
nSats 7.000 8.000 9.000 11.000 12.000 13.000 15.000 3.000 5.000 1.235 10.562 nSat 453.9 3603
TDOP 0.490 0.600 0.670 0.950 1.420 1.770 4.460 0.750 1.170 0.254 0.988 34.12 144.8

Local GPS. The Time Dilution of Precision (TDOP) is plotted in blue. The number of visible satellites (nSat) is plotted in red.

TDOP is field 3, and nSats is field 4, from the gpsd log file. The gpsd log file is created by the ntploggps program.

TDOP is a dimensionless error factor. Smaller numbers are better. TDOP ranges from 1 (ideal), 2 to 5 (good), to greater than 20 (poor). Some GNSS receivers report TDOP less than one which is theoretically impossible.



Server Offsets

peer offsets plot

The offset of all refclocks and servers. This can be useful to see if offset changes are happening in a single clock or all clocks together.

Clock Offset is field 5 in the peerstats log file.



Server Offset 2001:470:e815::23 (pi3.rellim.com)

peer offset 2001:470:e815::23 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2001:470:e815::23 (pi3.rellim.com) -90.174 -27.355 -12.915 31.539 63.529 103.337 130.441 76.444 130.692 24.460 29.125 µs 0.5602 4.898

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 2001:470:e815::8 (spidey.rellim.com)

peer offset 2001:470:e815::8 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 2001:470:e815::8 (spidey.rellim.com) -221.973 -54.293 -40.289 0.334 69.326 113.668 274.063 109.615 167.961 34.746 6.059 µs -1.928 8.268

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 204.17.205.1

peer offset 204.17.205.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.17.205.1 -771.981 -658.096 -505.849 -128.064 496.127 708.632 848.245 1,001.976 1,366.728 303.841 -92.298 µs -5.554 13.12

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 204.17.205.16

peer offset 204.17.205.16 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.17.205.16 -969.598 -922.753 -868.484 -666.272 -303.418 -250.874 -173.893 565.066 671.879 185.923 -629.354 µs -97.09 480.3

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 204.17.205.24

peer offset 204.17.205.24 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.17.205.24 -170.101 -55.451 -31.733 27.378 81.264 93.063 120.186 112.997 148.514 30.823 26.397 µs -0.7956 4.907

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 204.17.205.27

peer offset 204.17.205.27 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.17.205.27 -10.508 -0.072 -0.061 -0.027 -0.006 0.046 56.323 0.055 0.118 1.151 0.002 ms 31.66 1403

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset 204.17.205.30

peer offset 204.17.205.30 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset 204.17.205.30 -39.157 -22.787 -10.526 18.850 35.998 83.289 132.576 46.524 106.076 16.949 16.303 µs 1.156 10.54

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset SHM(0)

peer offset SHM(0) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset SHM(0) -52.651 -45.255 -42.570 -32.946 -24.749 -22.588 -16.506 17.821 22.667 5.437 -33.040 ms -375.9 2817

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Offset SHM(1)

peer offset SHM(1) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Offset SHM(1) -3.985 -2.220 -1.573 -0.261 3.148 5.127 9.681 4.721 7.347 1.421 -0.005 µs -2.133 7.869

The offset of a server in seconds. This is useful to see how the measured offset is behaving.

The chart also plots offset±rtt, where rtt is the round trip time to the server. NTP can not really know the offset of a remote chimer, NTP computes it by subtracting rtt/2 from the offset. Plotting the offset±rtt reverses this calculation to more easily see the effects of rtt changes.

Closer to 0s is better. An ideal system would be a horizontal line at 0s. Typical 90% ranges may be: local LAN server 80µs; 90% ranges for WAN server may be 4ms and much larger.

Clock Offset is field 5 in the peerstats log file. The Round Trip Time (rtt) is field 6 in the peerstats log file.



Server Jitters

peer jitters plot

The RMS Jitter of all refclocks and servers. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 2001:470:e815::23 (pi3.rellim.com)

peer jitter 2001:470:e815::23 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2001:470:e815::23 (pi3.rellim.com) 1.800 3.434 4.866 16.098 54.000 79.976 127.152 49.134 76.542 16.819 21.335 µs 2.515 8.75

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 2001:470:e815::8 (spidey.rellim.com)

peer jitter 2001:470:e815::8 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 2001:470:e815::8 (spidey.rellim.com) 3.118 5.631 8.593 25.457 75.503 115.678 239.625 66.910 110.047 22.777 31.579 µs 3.437 15.85

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 204.17.205.1

peer jitter 204.17.205.1 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.17.205.1 3.774 7.635 11.059 26.286 88.515 116.424 157.151 77.456 108.789 26.476 36.697 µs 2.53 6.865

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 204.17.205.16

peer jitter 204.17.205.16 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.17.205.16 83.569 114.194 146.551 258.417 397.623 448.622 531.319 251.072 334.428 79.303 264.296 µs 19.96 67.21

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 204.17.205.24

peer jitter 204.17.205.24 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.17.205.24 1.248 2.830 4.066 15.439 64.868 81.213 136.263 60.802 78.383 19.766 23.084 µs 1.834 5.342

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 204.17.205.27

peer jitter 204.17.205.27 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.17.205.27 0.000 0.002 0.003 0.011 0.044 0.069 41.612 0.040 0.067 0.902 0.046 ms 31.67 1264

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter 204.17.205.30

peer jitter 204.17.205.30 plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter 204.17.205.30 2.523 6.434 8.763 18.181 42.042 58.360 245.490 33.279 51.926 11.818 21.155 µs 6.255 54.33

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter SHM(0)

peer jitter SHM(0) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter SHM(0) 0.222 0.626 0.899 2.119 4.762 6.308 10.611 3.863 5.683 1.224 2.382 ms 4.954 16.26

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Server Jitter SHM(1)

peer jitter SHM(1) plot

Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Server Jitter SHM(1) 0.028 0.065 0.087 0.187 0.647 1.740 4.914 0.560 1.675 0.294 0.266 µs 5.085 43.69

The RMS Jitter of a server. Jitter is the current estimated dispersion, in other words the variation in offset between samples.

Closer to 0s is better. An ideal system would be a horizontal line at 0s.

RMS Jitter is field 8 in the peerstats log file.



Summary


Percentiles...... Ranges...... Skew- Kurt-
Name Min1%5%50%95% 99%Max   90%98%StdDev  MeanUnits nessosis
Local Clock Frequency Offset -6.387 -6.340 -6.273 -5.980 -5.761 -5.684 -5.674 0.512 0.656 0.153 -5.995 ppm -6.48e+04 2.606e+06
Local Clock Time Offset -3.984 -2.219 -1.572 -0.260 3.147 5.126 9.680 4.719 7.345 1.420 -0.005 µs -2.131 7.87
Local RMS Frequency Jitter 0.020 0.033 0.044 0.183 0.784 1.253 1.911 0.740 1.220 0.242 0.248 ppb 2.824 12.69
Local RMS Time Jitter 66.000 96.000 111.000 158.000 334.000 538.000 899.000 223.000 442.000 79.425 177.223 ns 8.905 45.65
Server Jitter 2001:470:e815::23 (pi3.rellim.com) 1.800 3.434 4.866 16.098 54.000 79.976 127.152 49.134 76.542 16.819 21.335 µs 2.515 8.75
Server Jitter 2001:470:e815::8 (spidey.rellim.com) 3.118 5.631 8.593 25.457 75.503 115.678 239.625 66.910 110.047 22.777 31.579 µs 3.437 15.85
Server Jitter 204.17.205.1 3.774 7.635 11.059 26.286 88.515 116.424 157.151 77.456 108.789 26.476 36.697 µs 2.53 6.865
Server Jitter 204.17.205.16 83.569 114.194 146.551 258.417 397.623 448.622 531.319 251.072 334.428 79.303 264.296 µs 19.96 67.21
Server Jitter 204.17.205.24 1.248 2.830 4.066 15.439 64.868 81.213 136.263 60.802 78.383 19.766 23.084 µs 1.834 5.342
Server Jitter 204.17.205.27 0.000 0.002 0.003 0.011 0.044 0.069 41.612 0.040 0.067 0.902 0.046 ms 31.67 1264
Server Jitter 204.17.205.30 2.523 6.434 8.763 18.181 42.042 58.360 245.490 33.279 51.926 11.818 21.155 µs 6.255 54.33
Server Jitter SHM(0) 0.222 0.626 0.899 2.119 4.762 6.308 10.611 3.863 5.683 1.224 2.382 ms 4.954 16.26
Server Jitter SHM(1) 0.028 0.065 0.087 0.187 0.647 1.740 4.914 0.560 1.675 0.294 0.266 µs 5.085 43.69
Server Offset 2001:470:e815::23 (pi3.rellim.com) -90.174 -27.355 -12.915 31.539 63.529 103.337 130.441 76.444 130.692 24.460 29.125 µs 0.5602 4.898
Server Offset 2001:470:e815::8 (spidey.rellim.com) -221.973 -54.293 -40.289 0.334 69.326 113.668 274.063 109.615 167.961 34.746 6.059 µs -1.928 8.268
Server Offset 204.17.205.1 -771.981 -658.096 -505.849 -128.064 496.127 708.632 848.245 1,001.976 1,366.728 303.841 -92.298 µs -5.554 13.12
Server Offset 204.17.205.16 -969.598 -922.753 -868.484 -666.272 -303.418 -250.874 -173.893 565.066 671.879 185.923 -629.354 µs -97.09 480.3
Server Offset 204.17.205.24 -170.101 -55.451 -31.733 27.378 81.264 93.063 120.186 112.997 148.514 30.823 26.397 µs -0.7956 4.907
Server Offset 204.17.205.27 -10.508 -0.072 -0.061 -0.027 -0.006 0.046 56.323 0.055 0.118 1.151 0.002 ms 31.66 1403
Server Offset 204.17.205.30 -39.157 -22.787 -10.526 18.850 35.998 83.289 132.576 46.524 106.076 16.949 16.303 µs 1.156 10.54
Server Offset SHM(0) -52.651 -45.255 -42.570 -32.946 -24.749 -22.588 -16.506 17.821 22.667 5.437 -33.040 ms -375.9 2817
Server Offset SHM(1) -3.985 -2.220 -1.573 -0.261 3.148 5.127 9.681 4.721 7.347 1.421 -0.005 µs -2.133 7.869
TDOP 0.490 0.600 0.670 0.950 1.420 1.770 4.460 0.750 1.170 0.254 0.988 34.12 144.8
Temp ZONE0 40.780 41.856 42.932 45.084 47.774 48.850 49.388 4.842 6.994 1.587 45.299 °C
nSats 7.000 8.000 9.000 11.000 12.000 13.000 15.000 3.000 5.000 1.235 10.562 nSat 453.9 3603
Summary as CSV file


This server:

CPU: Rasberry Pi 3
OS: Gentoo stable
Kernel: 4.4.45, Config
GPS; RPI GPS Add-on V2 GPS HAT
GPS/PPS server: gpsd
NTP server: NTPsec
ntp.conf: current

Notes:

22:00 10 Feb 2017 UTC Change kernel PREEMTP Server to Low Latency
00:00  3 Feb 2017 Cloned from pi4

Glossary:

frequency offset:
The difference between the ntpd calculated frequency and the local system clock frequency (usually in parts per million, ppm)
jitter, dispersion:
The short term change in a value. NTP measures Local Time Jitter, Refclock Jitter, and Server Jitter in seconds. Local Frequency Jitter is in ppm or ppb.
kurtosis, Kurt:
The kurtosis of a random variable X is the fourth standardized moment and is a dimension-less ratio. ntpviz uses the Pearson's moment coefficient of kurtosis. A normal distribution has a kurtosis of three. NIST describes a kurtosis over three as "heavy tailed" and one under three as "light tailed".
ms, millisecond:
One thousandth of a second = 0.001 seconds, 1e-3 seconds
mu, mean:
The arithmetic mean: the sum of all the values divided by the number of values. The formula for mu is: "mu = (∑xi) / N". Where xi denotes the data points and N is the number of data points.
ns, nanosecond:
One billionth of a second, also one thousandth of a microsecond, 0.000000001 seconds and 1e-9 seconds.
percentile:
The value below which a given percentage of values fall.
ppb, parts per billion:
Ratio between two values. These following are all the same: 1 ppb, one in one billion, 1/1,000,000,000, 0.000,000,001, 1e-9 and 0.000,000,1%
ppm, parts per million:
Ratio between two values. These following are all the same: 1 ppm, one in one million, 1/1,000,000, 0.000,001, and 0.000,1%
‰, parts per thousand:
Ratio between two values. These following are all the same: 1 ‰. one in one thousand, 1/1,000, 0.001, and 0.1%
refclock:
Reference clock, a local GPS module or other local source of time.
remote clock:
Any clock reached over the network, LAN or WAN. Also called a peer or server.
time offset:
The difference between the ntpd calculated time and the local system clock's time. Also called phase offset.
σ, sigma:
Sigma denotes the standard deviation (SD) and is centered on the arithmetic mean of the data set. The SD is simply the square root of the variance of the data set. Two sigma is simply twice the standard deviation. Three sigma is three times sigma. Smaller is better.
The formula for sigma is: "σ = √[ ∑(xi-mu)^2 / N ]". Where xi denotes the data points and N is the number of data points.
skewness, Skew:
The skewness of a random variable X is the third standardized moment and is a dimension-less ratio. ntpviz uses the Pearson's moment coefficient of skewness. Wikipedia describes it best: "The qualitative interpretation of the skew is complicated and unintuitive."
A normal distribution has a skewness of zero.
upstream clock:
Any server or reference clock used as a source of time.
µs, us, microsecond:
One millionth of a second, also one thousandth of a millisecond, 0.000,001 seconds, and 1e-6 seconds.



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