NtpServer accuracy introduction

  • Our GPS Server time and date is joined with GPS UTC system time.
  • GPS system time is under Atomic Cesium Clocks accuracy.
  • Follow www.nist.gov for atomic clock description
  • GPS receiver 1 sec UTC epochal accuracy is 300nsec.
  • This means, that every rising edge of 1sec pulse has max error +/- 300 nsec to UTC rising edge pulse.
  • This accuracy assumes minimal 5 satellites signal from power on reset. Otherwise rising edge 1sec accuracy is not guaranteed. In other words Time Server from power on reset to first fix within 5 sats not guaranteed 1sec epochal accuracy.

NTP Time accuracy

NTP time counter is represented in 64bit data format:

  • NTP time counter is represented in 64bit data format.
  • 32 bit for fractional part of second

Therefore fractional theoretical NTP resolution is equal to: 1/2^32 = 200psec.

Internal Time server stamp processor counter, working on frequency 76kHz, and thereby practical resolution is 1/76000 sec = 13.2 usec.

NTP response processor calculates from above stamp resolution to 32bit time stamp.

NTP protocol version 3.

This is the main base built in protocol of GPS Time server. NTP Network Time Protocol is described on official web site - www.ntp.org

All devices can synchronize local time to GPS NTP time server.