GNSS Applications (Precise Timing 1)

In addition to longitude, latitude, and altitude, the GNSS systems provide a critical fourth dimension – time. Each GNSS satellite carries two atomic clocks that contribute very precise time data to the GNSS signals. GNSS receivers decode these signals, effectively synchronising each receiver to the atomic clocks. This enables users to determine the time to within 100 billionths of a second, without the cost of owning and operating atomic clocks.

In June 2012, at the US Track & Field Trials for the London Olympics, Allyson Felix and

Jeneba crossed the finishing line of the 100m both with a time of 11.068 seconds. Even using a high speed camera shooting

3,000 frames per second (fps), the pair could not be separated. 3,0000 fps is ~3 times faster than the time

it takes the average human to blink an eye; however, even this is slow when compared to GNSS time, which can measure time in nanoseconds, that is one billionth of a second

To put nanoseconds into perspective, if a nanosecond was scaled up to one second, at this scale a second would be 31 years long. Other units of time include: Decisecond 0.1s

Centisecond 0.01s Millisecond 0.001s Microsecond 10-6s -9 Nanosecond 10 s Picosecond 10-12s

Femtosecond 10-15s The Planck Time Unit (5.39 × 10-44s) is Attosecond 10-18s (the shortest the time it takes light to travel one -35 length of time currently measurable) Planck length (1.616199 × 10 m)

GNSS Applications (Financial Markets) ‘Time is money’ so the saying goes and with the advent of GPS (Global Positioning System) becoming publicly available in 1983, this has become increasingly true in a truly surprising way. All the financial transactions in the world conducted electronically are now time stamped using GPS time. This is critical when the sums of money are huge; knowing who owns what and at what interest rate or at what price can potentially mean the difference between making or losing millions in less than the blink of an eye.

On the afternoon of May 6, 2010, starting at 2:42 p.m. EDT (Eastern Daylight Time), the value of the New York Dow Jones stock index dropped by $1 trillion in just 6 minutes. This was the deepest single-day decline in that market’s 114-year history. By 3:07 p.m., the index had rebounded. To put this in perspective, from the chart opposite, if you owned one share in Procter & Gamble worth $55 and sold it at 14:36:30, bought it back at 14:47:15 and then sold it again at 14:48:12, you would have earned $36.32 in just over 11 minutes. With public access to GPS time and the invention of super- fast computer chips, trading on the financial markets now occur at <950milliseconds, too fast to be conducted by humans. Instead, computer algorithms analyse the market buying and selling according to market trends, with instructions from the trader’s computer travelling to the market at the speed of light. At these sorts of speeds, the distance a trader’s computer iiss from the market is critical; a message from a trader 1km from the market will take 16microseconds longer than one from a trader 500m distant. For this reason, market and traders are now often co-located in the same building.