Lockheed Martin Corp. said yesterday that it had won a $1.46 billion contract to build next-generation global-positioning satellites, with a big chunk of the work planned for the Philadelphia suburbs.

The first contract, awarded by the Air Force, is for the first two of the initial constellation of eight orbiting spacecraft, designated GPS-IIIA, which will begin replacing GPS-II satellites in 2014.

The program envisions 16 more - eight GPS-IIIBs and eight GPS-IIICs.

The spacecraft are designed to be more resistant to attacks that could disrupt the system's increasingly vital service to the military and private commerce.

Lockheed's Commercial Space Systems complex in Newtown, Bucks County, will get 30 percent of the work, said U.S. Rep. Patrick Murphy (D., Bucks), who said he worked to steer the project to his district as a member of the House Armed Services Committee.

Lockheed's King of Prussia Space Systems unit is also expected to participate, but the company would not say last night to what extent.

Winning the contract gives Lockheed a leg up over rival Boeing Co., which has been a more prolific builder of satellites, for future work on the massive GPS program.

Many details about improvements the next-generation GPS will bring are classified.

But it is clear the system is intended to allow the military to be more precise in hitting targets. It will also let commercial and individual users - on land, water or in the air - more precisely determine their location, even moving at high speeds. Existing technology is already accurate to within 3.28 feet.

A constellation of orbiting satellites accomplishes this feat by precisely determining each satellite's location in space, based on signals from land stations. The satellites in turn broadcast precise time-and-location signals. GPS receivers, in a growing variety of devices, triangulate data from multiple satellites.

Many new cars, trucks and airplanes come equipped with GPS navigation devices. The technology is also at the heart of robotic farm equipment as well as cargo tracking and security systems.

Lockheed Martin has more than 12,000 employees in the Philadelphia region. Besides Newtown and King of Prussia, its major operations include ballistic missile defense, homeland security, and logistics programs in Moorestown and its Advanced Technology Laboratories and Information systems units in Cherry Hill.

Lockheed shares closed at $109.06, up 35 cents.