A Journey Through Time and Space: The History of Measurement

As part of its work in air and space, the team at To70 is always interested in accurate time and position measurements. Whether that be interpreting radar or Flight Data Recorder information or plotting co-ordinates in different geospatial datums, the accuracy of data drives our work. To70’s senior safety consultant and amateur historian, Adrian Young looks at the history of measuring x, y, z and T.

The quest to measure time and position has been integral to human development, enabling advancements in navigation, agriculture, and science. The earliest known timekeeping devices date back to ancient civilizations. The Egyptians, for instance, used obelisks and sundials around 3500 BCE to track the movement of the sun, dividing the day into measurable parts. For a multitude of reasons, many described in David Duncan’s excellent 1998 book, Calendar, a significant leap in European timekeeping didn’t come about until the 14th century, when mechanical clocks began to appear in monasteries and towns.

Whilst the early age of measurement was driven by religion, it was transport and travel that drove it on from the 17th and 18th centuries. Navigators relied on the stars, using tools like the astrolabe and sextant, to determine their latitude. However, determining longitude remained a challenge. The famous Longitude Act of 1714 offered a reward for a practical solution, spurring innovation. John Harrison's marine chronometer, developed in the mid-18th century, revolutionized navigation by allowing sailors to keep precise time at sea, essential for calculating longitude accurately. Those that have not visited the Royal Observatory in London, have missed seeing these iconic timepieces; accurate to three seconds a day on a rolling & pitching ship. The train brought standardised time in the 19th century, with concepts like universal time; GMT, was introduced in 1884 ahead of Coordinated Universal Time (UTC) or Zulu time in aviation (from 1960 onwards).

In aviation, accuracy has increased over time too. Loran-C, a low frequency radio navigation system, could achieve positional accuracies of about 500 metres in the middle of the 20th century. Modern positioning took a giant leap forward with the development of the satellite navigation systems. The first was the Global Positioning System (GPS) developed by the United States Department of Defense. Since the 1980s, its accuracy, achieved by triangulating signals from a network of satellites in space, allows users to pinpoint their exact location anywhere on the planet with remarkable accuracy, in some cases around 30 cm. The European Galileo system, China’s Beidou system and Russian GLONASS system means that there are currently just over 100 navigation satellites orbiting the Earth at ?an altitude of about 20 000 km.

In aviation, whilst satellite systems delivers data accuracy down to tens of metres, the required accuracy of the procedure types that are applied for customers by our Instrument Flight Procedure design teams are usually stated in nautical miles or fractions thereof.

At a recent (summer 2024) meeting at the Netherlands Space Office, it became clear that some users of satellite position data require much more accuracy; down to a couple of metres. Full details were not shared, but Justice Ministry staff hope to track those convicted and wearing such bracelets to within a few metres of their true position. There is always someone needing a more accurate data signal than you!

Where the future of time and position accuracy will go is not wholly clear. The future will bring even greater precision. For example, quantum clocks, which utilize the properties of quantum mechanics, promise to surpass atomic clocks in accuracy. However, with the current menace of intended and unintended jamming of navigation equipment, traditional navigation aids; tried and tested equipment such as VOR and DME, will be needed to create a safe and robust back-up.

Future developments in satellite guidance for aviation may see CAT II/III operations with augmented GNSS doing away with expensive ground equipment and we see satellite guidance being useful in geo-fencing drone operations.

The history of time and position measurement reflects humanity's relentless pursuit of greater accuracy and understanding. As society continues to push the boundaries of precision, we open new possibilities for the future and To70 stands by its clients to support aviation policy makers and operational staff with advice and flight procedure designs.