In the 1990s, soldiers in the Gulf War were equipped with GPS technology that transformed their ability to manoeuvre in a featureless, unmapped landscape. How did the use of satellite navigation affect the conflict, as well as civilian life?
What is GPS?
GPS stands for Global Positioning System. It is a method of satellite navigation which can be used to pinpoint the user’s location anywhere in the world. GPS uses signals transmitted from satellites orbiting Earth.
Signals transmitted from different satellites simultaneously will reach a point on the ground at slightly different times. A GPS receiver computes its location from a combination of these time differences and the known bearings of the satellites.
Why was new navigation technology needed?
Navigating in the desert is like navigating a ship at sea: your only points of reference are the positions of the Sun, stars and planets. You need to keep track of your compass bearing and the distance you have covered, and plot your position on a map.
This method is known as ‘dead reckoning’. It was how, in August 1990 during the First Gulf War, American, British and other coalition troops arriving in Saudi Arabia en route to Kuwait had been trained to navigate.
To measure the distance they had travelled, they learned to count the number of paces they took to cover a kilometre. However, measuring distance travelled in a tank was more problematic. Although the soldiers had instruments to measure speed, it was difficult to drive in a straight line in soft sand, and this often led to errors.
To ensure a constant direction, soldiers took bearings from visible landmarks using a compass.
However, the metal hull of the tank interfered with the magnetic reading, so their progress was hampered by the need to stop and get out in order to use the compass.
Of course, there often were no landmarks: the desert is a constantly shifting landscape of dunes, rearranged with every sandstorm.
Despite their best efforts, soldiers often got lost. If they came across an oasis, one of the few features likely to be marked on a map, they saw it as a godsend.
How was GPS technology developed?
The American military had been experimenting with forms of GPS, for navigation at sea or missile targeting, since the 1960s.
The system in place today was initiated with the launch of the first NAVSTAR satellites in 1978. The idea was to establish a constellation of 24 satellites, guaranteeing that anywhere in the world you could receive signals from at least four.
By August 1990, when the troops went into Saudi Arabia, the constellation consisted of only 14 satellites, but the system was good enough to be useful.
How did GPS work in practice?
Publicly available GPS signals were deliberately scrambled so that they were accurate to only 100 metres or so—a practice known as Selective Availability.
Even so, GPS had already been adopted by the crews of ocean-going yachts.
Surprisingly, given that the US Department of Defense had funded the NAVSTAR network, it struggled to meet the need for multiple GPS receivers in the Gulf. Manufacturers rushed to make new receivers and send them out to the troops. Often there were as few as two instruments for 100 vehicles.
Some soldiers relied on members of their families to buy civilian GPS systems and ship them out—even though these were less accurate.
Recognising this, the American authorities temporarily turned off Selective Availability, so that civilian GPS receivers could locate positions accurately.
The military equipment was not well designed for use in a theatre of war—some tank crews and helicopter pilots stuck the devices to their vehicles with gaffer tape.
What was the impact of the technology?
Even the meal trucks that brought food to the soldiers on the front line used GPS to locate units quickly and easily. The most basic receivers did not incorporate maps, but gave an accurate reading of latitude and longitude, and an indicator to show which way you were going.
Despite its imperfections, the technology was enough to transform the progress of the coalition troops.
When did GPS become available to civilians?
With the war over, the American military reinstated Selective Availability. However, by this time, a huge civilian market had built up for GPS—partly influenced by the success of the technology in the Gulf.
In May 2000 President Bill Clinton authorised the army to discontinue the scrambling of signals, so that everyone could benefit from the pin-sharp accuracy of GPS data.
Satnav in cars and GPS-enabled chart plotters in boats, GPS-enabled cameras and now smartphones all mean that we no longer need to rely on maps, charts and compasses to know where we are.
We may still look to the sky, but the heavenly bodies we rely on are now electronic.