While public NTP servers provide decent time synchronization for most applications, GPS-based solutions offer several technical advantages:

• Atomic-clock accuracy: GPS satellites transmit time signals synchronized to atomic clocks with nanosecond precision
• Complete independence: Doesn't rely on network infrastructure or third-party servers
• Predictable latency:
  Fixed signal propagation time from satellites (unlike variable internet latency)

Here are three common approaches to implement GPS time sync:

1. Dedicated NTP server with GPS module:

# Sample chrony configuration for GPS time sync
refclock SHM 0 offset 0.0 delay 0.1 refid GPS 
server 0.pool.ntp.org iburst
server 1.pool.ntp.org iburst

2. Raspberry Pi with GPS dongle:

# Install required packages
sudo apt install gpsd gpsd-clients python-gps chrony

# Configure gpsd to use USB GPS
sudo systemctl stop gpsd.socket
sudo systemctl disable gpsd.socket
sudo gpsd /dev/ttyUSB0 -F /var/run/gpsd.sock

3. Commercial GPS NTP appliances:
Products like Microchip's SyncServer or Meinberg's LANTIME offer enterprise-grade solutions with PPS outputs.

Consider GPS synchronization when:

• Your application requires <10ms accuracy
• You need audit-compliant timestamps
• Operating in environments with unreliable internet
• Building distributed systems requiring clock coherence

For applications requiring extreme precision:

// C code example for PPS (Pulse Per Second) handling
#include <sys/ioctl.h>
#include <linux/pps.h>

int fd = open("/dev/pps0", O_RDWR);
struct pps_fdata fdata;
ioctl(fd, PPS_FETCH, &fdata);
printf("Precise timestamp: %ld.%09ld\n", 
       fdata.info.assert_tu.sec, 
       fdata.info.assert_tu.nsec);

Remember that GPS signals require clear sky view - indoor applications may need roof-mounted antennas.

When building distributed systems, accurate timekeeping becomes crucial for:

• Transaction ordering in financial systems
• Log correlation across microservices
• Scientific data collection

Traditional NTP over internet introduces multiple points of potential drift:

// Example of typical NTP stratification
Stratum 0: Atomic clocks (GPS satellites)
Stratum 1: GPS-synchronized servers
Stratum 2: Servers syncing with Stratum 1
Stratum 3+: Increasingly unreliable hops

A Raspberry Pi with GPS module can achieve Stratum 1 accuracy:

# GPSD configuration for NTP
sudo apt install gpsd gpsd-clients python-gps
sudo systemctl enable gpsd
sudo nano /etc/default/gpsd
# Add:
GPSD_OPTIONS="/dev/ttyACM0"
START_DAEMON="true"

Compared to internet NTP, GPS provides:

For mission-critical systems, consider fallback mechanisms:

// NTP configuration with GPS priority
server 127.127.28.0 minpoll 4 maxpoll 4 prefer
fudge 127.127.28.0 time1 0.420 refid GPS

# Internet fallback servers
server 0.pool.ntp.org iburst
server 1.pool.ntp.org iburst

Real-world latency measurements show:

• GPS lock time: 30-120 seconds (cold start)
• Internet NTP convergence: 2-5 minutes
• Long-term drift: GPS maintains <1μs, Internet varies by 5-100ms

Consider GPS time sources when:

1. Operating in regulated industries (FINRA, MiFID II)
2. Running high-frequency trading systems
3. Maintaining distributed databases across continents

For most web applications, internet NTP suffices. But as Kubernetes architect Martin Fowler notes: "Distributed systems should never trust local clocks - GPS provides the only truly authoritative time source."