What is the main idea of the passage?

Gladys West’s careful satellite calculations helped build the Earth models that later supported GPS. (The passage traces West’s mathematical work from satellite data to the Earth models used by GPS.)

Why did West need many measurements to model Earth?

Earth is not a perfect ball. (The text directly explains that Earth’s uneven shape requires many measurements.)

What does “foundation” mean in the final paragraph?

an underlying part that later work depends on (West’s models were an underlying basis for later GPS technology, not a building floor.)

Where did West begin working in 1956?

at a United States Navy laboratory (The opening paragraph says she joined a United States Navy laboratory in 1956.)

Gladys West Measures the Earth: Level 1 Reading Comprehension Questions

Gladys West grew up on a farm in Virginia. She excelled in mathematics at school. After college, she joined a United States Navy laboratory in 1956. Few women there did complex calculations.

West studied information sent by satellites. Earth is not a perfect ball, so finding its exact shape requires many measurements. West helped turn satellite observations into mathematical models of the planet. She checked results and improved the calculations as information arrived.

Those models later supported the Global Positioning System, or GPS. A phone can show a location only because satellites and receivers agree on a detailed model of Earth. West did not build a map app. Her patient work created part of the mathematical foundation beneath it. Years later, her contribution became widely known. Her story shows that a familiar tool may rest on careful work most users never see.

Comprehension questions