This "project" provides status monitoring and graph visualization for two Raspberry Pi devices running ADS-B flight tracking and NTP time server services.
ADS-B (Automatic Dependent Surveillance-Broadcast) —
Aircraft broadcast their position, altitude, speed, and flight number via radio.
A Raspberry Pi with a software-defined radio receiver picks up these signals
and displays live air traffic on a map.
NTP (Network Time Protocol) —
A protocol used to synchronize computer clocks over a network.
This server uses a GPS receiver as a precise time source and acts as Stratum 1 to provide accurate time to other devices on the local network.
Pi 3B — ADS-B Feeder
This is an example of my "radar" screen with info I get from the ADS-B signal. (refreshed every 10 min)
Updated: 2026-08-19 15:53
Pi 5 — NTP Server
An example of some information the chrony software provides on the Pi 5 about the NTP server with GPS timing. (refreshed every 5 min)
=== CHRONY SOURCES (GPS & PPS only) ===
.-- Source mode '^' = server, '=' = peer, '#' = local clock.
/ .- Source state '*' = current best, '+' = combined, '-' = not combined,
| / 'x' = may be in error, '~' = too variable, '?' = unusable.
|| .- xxxx [ yyyy ] +/- zzzz
|| Reachability register (octal) -. | xxxx = adjusted offset,
|| Log2(Polling interval) --. | | yyyy = measured offset,
|| \ | | zzzz = estimated error.
|| | | \
MS Name/IP address Stratum Poll Reach LastRx Last sample
===============================================================================
#- GPS 0 4 377 15 -124ms[ -124ms] +/- 200ms
#* PPS 0 4 377 14 +695ns[+1158ns] +/- 90ns
=== CHRONY TRACKING ===
Reference ID : 50505300 (PPS)
Stratum : 1
Ref time (UTC) : Wed Aug 19 14:00:46 2026
System time : 0.000000323 seconds fast of NTP time (*)
Last offset : +0.000000473 seconds (*)
RMS offset : 0.000001748 seconds
Frequency : 0.619 ppm slow (*)
Residual freq : +0.001 ppm
Skew : 0.066 ppm
Root delay : 0.000000001 seconds
Root dispersion : 0.000016263 seconds
Update interval : 16.0 seconds
Leap status : Normal
(*) values used in NTP graphs
=== CHRONY SOURCESTATS (GPS & PPS only) ===
.- Number of sample points in measurement set.
/ .- Number of residual runs with same sign.
| / .- Length of measurement set (time).
| | / .- Est. clock freq error (ppm).
| | | / .- Est. error in freq.
| | | | / .- Est. offset.
| | | | | | On the -.
| | | | | | samples. \
| | | | | | |
Name/IP Address NP NR Span Frequency Freq Skew Offset Std Dev
==============================================================================
GPS 64 45 1006 +20.227 63.321 -112ms 43ms
PPS 6 3 80 +0.001 0.069 +4ns 581ns
chronyc (chrony) version 4.3 (+READLINE +SECHASH +IPV6 -DEBUG)
Generated at 2026-08-19 16:01:02
Updated: 2026-08-19 16:01
