NTPsec

Pi5/Uputronics

Report generated: Mon May 25 05:43:07 2020 UTC
Start Time: Sun May 24 05:43:02 2020 UTC
End Time: Mon May 25 05:43:02 2020 UTC
Report Period: 1.0 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 -2.645 -1.913 -1.411 -0.107 2.609 4.085 7.886 4.020 5.998 1.227 0.043 µs -2.283 7.703
Local Clock Frequency Offset -6.180 -6.175 -6.159 -5.845 -5.617 -5.616 -5.615 0.542 0.559 0.174 -5.848 ppm -4.124e+04 1.427e+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 97.000 111.000 156.000 316.000 529.000 841.000 205.000 432.000 76.396 173.831 ns 9.493 51.23

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 22.000 27.000 37.000 195.000 665.000 993.000 1,431.000 628.000 966.000 193.503 229.315 10e-12 2.964 13.25

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 -2.645 -1.913 -1.411 -0.107 2.609 4.085 7.886 4.020 5.998 1.227 0.043 µs -2.283 7.703

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 -6.180 -6.175 -6.159 -5.845 -5.617 -5.616 -5.615 0.542 0.559 0.174 -5.848 ppm -4.124e+04 1.427e+06
Temp ZONE0 42.932 42.932 44.008 47.236 49.388 49.926 49.926 5.380 6.994 1.892 46.864 °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 13.000 13.000 14.000 4.000 5.000 1.239 10.625 nSat 458 3645
TDOP 0.530 0.590 0.660 0.940 1.400 1.690 3.270 0.740 1.100 0.247 0.981 36.29 153.1

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) -31.891 -27.214 -13.178 31.141 59.488 106.713 171.689 72.666 133.927 24.876 28.192 µs 0.9513 7.17

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) -193.198 -57.331 -44.228 0.562 69.274 101.531 233.361 113.502 158.862 36.668 5.980 µs -2.492 8.943

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 -769.802 -757.506 -733.717 -272.718 359.545 455.860 519.961 1,093.262 1,213.366 319.516 -215.563 µs -9.439 25.09

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 -958.983 -896.954 -874.362 -675.532 -290.150 -213.769 -135.532 584.212 683.185 191.564 -633.395 µs -92.31 449.1

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 -56.561 -45.972 -29.041 28.014 82.357 92.991 123.580 111.398 138.963 31.031 28.367 µs -0.3218 3.367

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 -72.665 -65.378 -43.291 -24.575 -0.749 46.480 60.606 42.542 111.858 16.088 -23.883 µs -20.86 66.93

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 -20.696 -16.806 -5.639 19.441 35.574 95.575 114.575 41.213 112.381 15.596 17.941 µs 2.437 14.94

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) -48.555 -45.664 -42.847 -33.193 -25.046 -22.801 -16.948 17.801 22.863 5.347 -33.379 ms -401.9 3074

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) -2.646 -1.914 -1.412 -0.108 2.610 4.086 7.887 4.022 6.000 1.228 0.043 µs -2.285 7.701

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) 2.571 3.141 4.538 15.951 54.733 74.512 128.814 50.195 71.371 17.182 21.266 µs 2.558 10.16

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) 3.228 6.381 9.198 29.197 75.796 109.530 257.599 66.598 103.149 23.635 34.149 µs 4.215 26.02

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 4.116 7.224 12.108 30.742 97.335 131.072 307.869 85.227 123.848 32.466 42.675 µs 3.486 20.61

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 97.037 110.046 143.989 267.318 414.194 469.071 587.482 270.205 359.025 84.049 270.178 µs 17.8 58.81

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 1.709 2.782 4.175 17.128 66.276 80.908 106.218 62.101 78.126 20.304 25.081 µs 1.742 4.564

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 1.454 2.463 3.506 9.891 39.658 66.486 102.007 36.152 64.023 12.404 13.539 µs 3.249 15.74

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 5.138 7.465 9.690 18.973 43.323 104.762 269.560 33.633 97.297 21.515 22.811 µs 8.308 90.46

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) 0.311 0.623 0.925 2.152 4.807 6.437 10.876 3.882 5.814 1.221 2.410 ms 5.176 17.56

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) 0.033 0.064 0.086 0.173 0.562 1.743 4.552 0.476 1.679 0.291 0.244 µs 5.854 54.92

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 -6.180 -6.175 -6.159 -5.845 -5.617 -5.616 -5.615 0.542 0.559 0.174 -5.848 ppm -4.124e+04 1.427e+06
Local Clock Time Offset -2.645 -1.913 -1.411 -0.107 2.609 4.085 7.886 4.020 5.998 1.227 0.043 µs -2.283 7.703
Local RMS Frequency Jitter 22.000 27.000 37.000 195.000 665.000 993.000 1,431.000 628.000 966.000 193.503 229.315 10e-12 2.964 13.25
Local RMS Time Jitter 66.000 97.000 111.000 156.000 316.000 529.000 841.000 205.000 432.000 76.396 173.831 ns 9.493 51.23
Server Jitter 2001:470:e815::23 (pi3.rellim.com) 2.571 3.141 4.538 15.951 54.733 74.512 128.814 50.195 71.371 17.182 21.266 µs 2.558 10.16
Server Jitter 2001:470:e815::8 (spidey.rellim.com) 3.228 6.381 9.198 29.197 75.796 109.530 257.599 66.598 103.149 23.635 34.149 µs 4.215 26.02
Server Jitter 204.17.205.1 4.116 7.224 12.108 30.742 97.335 131.072 307.869 85.227 123.848 32.466 42.675 µs 3.486 20.61
Server Jitter 204.17.205.16 97.037 110.046 143.989 267.318 414.194 469.071 587.482 270.205 359.025 84.049 270.178 µs 17.8 58.81
Server Jitter 204.17.205.24 1.709 2.782 4.175 17.128 66.276 80.908 106.218 62.101 78.126 20.304 25.081 µs 1.742 4.564
Server Jitter 204.17.205.27 1.454 2.463 3.506 9.891 39.658 66.486 102.007 36.152 64.023 12.404 13.539 µs 3.249 15.74
Server Jitter 204.17.205.30 5.138 7.465 9.690 18.973 43.323 104.762 269.560 33.633 97.297 21.515 22.811 µs 8.308 90.46
Server Jitter SHM(0) 0.311 0.623 0.925 2.152 4.807 6.437 10.876 3.882 5.814 1.221 2.410 ms 5.176 17.56
Server Jitter SHM(1) 0.033 0.064 0.086 0.173 0.562 1.743 4.552 0.476 1.679 0.291 0.244 µs 5.854 54.92
Server Offset 2001:470:e815::23 (pi3.rellim.com) -31.891 -27.214 -13.178 31.141 59.488 106.713 171.689 72.666 133.927 24.876 28.192 µs 0.9513 7.17
Server Offset 2001:470:e815::8 (spidey.rellim.com) -193.198 -57.331 -44.228 0.562 69.274 101.531 233.361 113.502 158.862 36.668 5.980 µs -2.492 8.943
Server Offset 204.17.205.1 -769.802 -757.506 -733.717 -272.718 359.545 455.860 519.961 1,093.262 1,213.366 319.516 -215.563 µs -9.439 25.09
Server Offset 204.17.205.16 -958.983 -896.954 -874.362 -675.532 -290.150 -213.769 -135.532 584.212 683.185 191.564 -633.395 µs -92.31 449.1
Server Offset 204.17.205.24 -56.561 -45.972 -29.041 28.014 82.357 92.991 123.580 111.398 138.963 31.031 28.367 µs -0.3218 3.367
Server Offset 204.17.205.27 -72.665 -65.378 -43.291 -24.575 -0.749 46.480 60.606 42.542 111.858 16.088 -23.883 µs -20.86 66.93
Server Offset 204.17.205.30 -20.696 -16.806 -5.639 19.441 35.574 95.575 114.575 41.213 112.381 15.596 17.941 µs 2.437 14.94
Server Offset SHM(0) -48.555 -45.664 -42.847 -33.193 -25.046 -22.801 -16.948 17.801 22.863 5.347 -33.379 ms -401.9 3074
Server Offset SHM(1) -2.646 -1.914 -1.412 -0.108 2.610 4.086 7.887 4.022 6.000 1.228 0.043 µs -2.285 7.701
TDOP 0.530 0.590 0.660 0.940 1.400 1.690 3.270 0.740 1.100 0.247 0.981 36.29 153.1
Temp ZONE0 42.932 42.932 44.008 47.236 49.388 49.926 49.926 5.380 6.994 1.892 46.864 °C
nSats 7.000 8.000 9.000 11.000 13.000 13.000 14.000 4.000 5.000 1.239 10.625 nSat 458 3645
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
19:00 21 Dec 2016 UTC SD corruption, start all over again...

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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