Geoid

High school (ages 12+)
Geography

Name:

Date:

Step 1 · Read the article

Open the article and read it at the level above. Then answer the questions below in your own words.

https://smallwhale.org/articles/geoid

Write what each word means, using the article.

Do not copy the article. Write two things you learned, the way you would explain them to a friend.

Answers below are taken from the article’s stored facts, so they match what the student read.

1. What is the determined by?Gravitational attraction of Earth's mass and centrifugal force from rotation
2. What is the reference for?Orthometric heights (heights above mean sea level)
3. Why does the geoid have bumps and dips?The bumps and dips come from places where there is more or less mass inside the Earth, such as big continents or ocean trenches. More mass pulls the surface up (positive undulation), less mass pulls it down (negative undulation).
4. How do scientists measure the geoid?Scientists use very precise gravity measurements from the ground and from satellites like GRACE and GOCE, and then use computers to build a model of the geoid.

Equipotential Surface: A surface where the gravitational potential energy of an object is constant.
Reference Ellipsoid: A simplified, smooth mathematical model of Earth's shape used as a base for mapping.
Gravitational Anomaly: The difference between the observed gravitational force and the force predicted by a reference model.
Orthometric Height: The height of a point above the geoid, representing actual elevation.