Prime Meridian Day – 135 years

October 13, 2019

Written by Editor

Sir George Airy established a meridian at the Royal Greenwich Observatory in 1851 to serve as a common reference for astronomical observations and navigation. By 1884 two thirds of ships were using it as a reference on their charts.

US President Chester A. Arthur hosted the International Meridian conference in Washington, DC that same year. 41 delegates from 25 countries attended.  On October 13th the conference selected the Greenwich Meridian as the international Prime Meridian.

France abstained from the vote and continued to use the Paris meridian as a reference for several decades.

If you are ever in London, Greenwich is a short boat ride down the Thames (you can also take the tube, but why would you do that?)  The Observatory has marvelous exhibits and the UK National Maritime Museum is right next door. A great way for navigators to spend the day.

 

What Can YOU Do? How Can YOU Help?

PNT is the quiet backbone of everything but too many leaders still don’t see the risk.

But you do. You understand the systems, the dependencies, the failure chains. That insight is rare — and it’s exactly what your country needs right now. Contact your government leaders and industry decision-makers and tell them resilient PNT isn’t a feature — it’s the foundation everything else depends on.

Start the Conversation

Use our Resilient PNT Key Talking Points to make the case.

U.S. Advocates

Find your representatives at Congress.gov, then use our email template to reach them in minutes.

When you get a response, let us know. Every conversation strengthens the mission.

More PNT News

PNT cyber guidance update – NIST wants your input

PNT cyber guidance update – NIST wants your input

Image: RNT Foundation What's new: Draft updated PNT cyber guidance from NIST. They are seeking public comment and input. Why it's important: PNT and cyber are well intertwined. PNT is an essential tech infrastructure so protecting it from malicious cyber effects is...

GPS Is Not Guaranteed: Impact on ports (Webinar 21 May)

GPS Is Not Guaranteed: Impact on ports (Webinar 21 May)

Image: Shutterstock What's new: A webinar featuring our colleague Matt Shirley. Matt is a professional port pilot and has some interesting insights on maritime reliance on GPS/GNSS, how things could go wrong without resilient PNT, and how things could go better with...

Intl Airline Pilots Assn calls for changes & GPS backup

Intl Airline Pilots Assn calls for changes & GPS backup

Image: Aircraft near Delhi, India being spoofed 5 Nov 2025 - GPSWise What's new: The International Federation of Air Line Pilots’ Associations (IFALPA) called for actions to combat GNSS disruption from ICAO, nations, air navigation service providers, manufacturers,...

What is system “resilience”?

What is system “resilience”?

Image: Shutterstock What's new: Discussion of system "resilience," especially in the context of PNT. Why it's important: We sometimes hear folks ask for a definition of "resilience." Many are genuinely seeking to define terms to help in identifying solutions. Others...

RNT Foundation Annual Meeting a Huge Success

RNT Foundation Annual Meeting a Huge Success

Image: RNT Foundation What's new: Our recent annual meeting was a huge success featuring: Comments from Department of Defense/War Assistant Secretary for Space Policy, Hon. Marc Berkowitz, Comments from Department of Transportation Acting Assistant Secretary for...

Get PNT News in Your Inbox