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The NOAA survey ship Thomas Jefferson is named after the third President of the United States who, in 1807, started the survey agency that would later become NOAA.

 

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Historical drawing of surveyor conducting lead line survey
A surveyor gets ready to cast a lead line. Lead line depths were usually taken from slow-moving boats and could take a long time.

How Did We Map the Sea Floor in the Past?

The first survey to map the sea floor in the United States was completed in 1834 on the south shore of Long Island, New York.

It was done using lead lines and sounding poles.

Lead lines were ropes with numbers marked along them, like a ruler. A lead weight was attached at the end.

Sounding poles are like big rulers.

Surveyors used these tools for a long time. A surveyor lowered a line into the ocean. When it hit the bottom, he marked the measurement and pulled it up. He wrote down measurements from different parts of the ocean. Then he put them on a chart to create a “picture” of the ocean floor. The measurements were often right, but the uncharted spaces between them were really big. Many objects were missed. Some were rocks as big as your house! These objects caused many shipwrecks.

Modern tools let us see all of the sea floor.


Historical drawing of wire-drag surveying method.
Historical drawing of wire-drag surveying method. Click image for larger view.

Did you know?

Surveyors also used a method of surveying called "wire-drag." Click on the image to learn more.









 






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