LOS ANGELES — Without it, ATMs would stop spitting out cash, Wall Street could blunder billions of dollars in stock trades and clueless drivers would get lost.

Most people may associate the Global Positioning System with the navigation devices that are becoming standard equipment on new cars. But GPS has become a nerve center for the 21st century rivaling the Internet — enabling cargo companies to track shipments, guiding firefighters to hot spots and even helping people find lost dogs.

"It's a ubiquitous utility that everybody takes for granted now," said Bradford W. Parkinson.

He should know. Three decades ago, as a baby-faced Air Force colonel just out of the Vietnam War, Parkinson led the Pentagon team that developed GPS at a military base in El Segundo, Calif.

Now, scientists and engineers — including those at a sprawling satellite-making factory in El Segundo — are developing an $8 billion GPS upgrade that will make the system more reliable, more widespread and much more accurate.

The new system is designed to pinpoint a location within an arm's length, compared with a margin of error of 20 feet or more today. With that kind of precision, a GPS-enabled mobile phone could guide you right to the front steps of Starbucks, rather than somewhere on the block.

"This new system has the potential to deliver capabilities we haven't seen yet," said Marco Caceres, senior space analyst for aerospace research firm Teal Group. "Because GPS touches so many industries, it's hard to imagine what industry wouldn't be affected."

The 24 satellites that make up the GPS constellation — many of them built at the former Rockwell plant in Seal Beach — will be replaced one by one. The first replacement was scheduled to be launched from Cape Canaveral this weekend. The overhaul will take a decade and is being overseen by engineers at Los Angeles Air Force Base in El Segundo, where Parkinson and his team developed the current system.

"We know that the world relies on GPS," said Col. David B. Goldstein, the chief engineer for the upgrade.

San Diego found out firsthand in 2007, when the Navy accidentally jammed GPS signals in the area, knocking out cell phone service and a hospital's emergency paging system for doctors.

New York experienced a similar problem a year later.

The upgrade is designed in part to prevent such outages by increasing the number of signals beamed to Earth from satellites orbiting 12,000 miles above.

By triangulating the signals from four satellites, GPS receivers — and there are now more than a billion of them — can pinpoint your exact location on the ground.

Although "positioning" is an obvious application of the technology, it's also become a crucial timekeeper for the financial industry.

Transactions made everywhere, as varied as ATM withdrawals and Wall Street stock trades, are time-stamped using precise atomic clocks ticking within the GPS satellites. The clocks are accurate to one-billionth of a second. It's a crucial technology for Wall Street, where a fraction of a second could mean billions of dollars.