Smart Bombs
Satellites Give U.S. Airstrikes Dead-On AimBy Ned Potter
March 22 — When the USS Bunker Hill, stationed in the Persian Gulf, launched some of the first missiles of the Iraq war, it got guidance from satellites 10,000 miles overhead.
In the first Gulf War 12 years ago, global positioning was used in about 10 percent of the airstrikes, but this time around, all the bombs and missiles dropped so far have been smart munitions.
The Pentagon has confirmed that the ship's missiles were aimed at military targets in downtown Baghdad. They hit with a level of precision measured in yards.
The problem was that those targets — like many in this war — were surrounded by buildings the United States wanted to leave intact.
To avoid hitting them, U.S. missiles have to rely on the Global Positioning System — GPS for short.
"The whole intent here is to maximize the impact on military targets while minimizing collateral damage," said U.S. Navy Capt. Scott Swift, aboard the USS Abraham Lincoln.
Plotting a Path The Global Positioning System is a constellation of satellites whose signals can be used to plot the location of any object on Earth. A missile uses the satellites' signals to plot the path to its target. The military says chances are better than 50-50 that the missile will hit within 40 feet of its intended target.
"In a crowded neighborhood, the difference between the satellite-guided bomb and the dumb bomb can be the difference between hitting the secret police headquarters, and hitting an orphanage," said John Pike, an ABCNEWS consultant who is also the director of GlobalSecurity.org.
Every platoon racing north into Iraq also has a GPS receiver. It is an essential tool to get thousands of troops across open desert. If soldiers know precisely where they are, and where their comrades are, it's less likely that they will fire on each other by accident.
Mistakes Are Part of Odds A soldier in an armored vehicle demonstrated how he had only to push on a touch screen to show his location.
"This basically tells me where all the other similarly equipped units are, all over the battlefield, so if they have the same type of computer, I can maintain situational awareness," he said.
But military analysts warn that no matter how smart the weapons, there will inevitably be mistakes.
If a particular building is targeted for destruction by a U.S. missile, the odds are about 50 percent that the warhead will go off within 40 feet of it. But that also means the odds are 50 percent that the weapon will miss, perhaps by enough to destroy civilian buildings.
"Even if every one of the 3,000 bombs that we say we're going to drop just hits one Iraqi, you're talking about 3,000 dead Iraqis," said Joseph Cirincione, director of the Non-Proliferation Project at the Carnegie Endowment for International Peace in Washington.
"A great deal depends on our intelligence," said Cirincione. "Did we really pick out the right targets? Is that really a Republican Guard barracks, and not a school?"
So GPS is a key tool in the U.S. arsenal. But for all the technology brought to bear, war is still an unpredictable business
http://abcnews.go.com/sections/wnt/World/iraq_GPS_030322.html____________________________________________________
It was also reported that the GPS signals can be interfered by external "electric noise", and can affect the accuracy of these weapons that depend on GPS guidance.
For Singapore to use GPS dependent weapon systems, we will be dependent on GPS satellites that are developed and owned largely by the USA, who can easily modify the codes and control its access.
While we may not need GPS satellites to cover the entire globe, it will be sufficient for our immediate theatre of expected operation.