## Earth geometry

##### DM-43 - Approximating the geoid with spheres and ellipsoids • Identify the parameters used to define an ellipsoid
• Differentiate the Clarke 1866 and WGS 84 ellipsoids in terms of ellipsoid parameters
• Differentiate between a bi-axial and tri-axial ellipsoid and their applications
• Explain why spheres and ellipsoids are used to approximate geoids
• Distinguish between a geoid, an ellipsoid, a sphere, and the terrain surface
• Describe an application for which it is acceptable to use a sphere rather than an ellipsoid
##### DM-42 - History of understanding Earth's shape • Describe how scientists’ understanding of the Earth’s shape has evolved throughout history
• Describe the contributions of key individuals (e.g., Eratosthenes, Newton, Picard, Bouguer, LaPlace, La Candamine) to scientists’ understanding of the Earth’s shape
• Explain how technological and mathematical advances have led to more sophisticated knowledge about the Earth’s shape
• Describe and critique early efforts to measure the Earth’s size and shape
##### DM-43 - Approximating the geoid with spheres and ellipsoids • Identify the parameters used to define an ellipsoid
• Differentiate the Clarke 1866 and WGS 84 ellipsoids in terms of ellipsoid parameters
• Differentiate between a bi-axial and tri-axial ellipsoid and their applications
• Explain why spheres and ellipsoids are used to approximate geoids
• Distinguish between a geoid, an ellipsoid, a sphere, and the terrain surface
• Describe an application for which it is acceptable to use a sphere rather than an ellipsoid
##### DM-44 - Approximating the Earth's shape with geoids • Explain why gravity varies over the Earth’s surface
• Explain how geoids are modeled
• Explain the role that the U.S. National Geodetic Survey plays in maintaining and developing geoid models
• Explain the concept of an equipotential gravity surface (i.e., a geoid)
##### DM-42 - History of understanding Earth's shape • Describe how scientists’ understanding of the Earth’s shape has evolved throughout history
• Describe the contributions of key individuals (e.g., Eratosthenes, Newton, Picard, Bouguer, LaPlace, La Candamine) to scientists’ understanding of the Earth’s shape
• Explain how technological and mathematical advances have led to more sophisticated knowledge about the Earth’s shape
• Describe and critique early efforts to measure the Earth’s size and shape
##### DM-44 - Approximating the Earth's shape with geoids • Explain why gravity varies over the Earth’s surface
• Explain how geoids are modeled
• Explain the role that the U.S. National Geodetic Survey plays in maintaining and developing geoid models
• Explain the concept of an equipotential gravity surface (i.e., a geoid)
##### DM-43 - Approximating the geoid with spheres and ellipsoids • Identify the parameters used to define an ellipsoid
• Differentiate the Clarke 1866 and WGS 84 ellipsoids in terms of ellipsoid parameters
• Differentiate between a bi-axial and tri-axial ellipsoid and their applications
• Explain why spheres and ellipsoids are used to approximate geoids
• Distinguish between a geoid, an ellipsoid, a sphere, and the terrain surface
• Describe an application for which it is acceptable to use a sphere rather than an ellipsoid
##### DM-42 - History of understanding Earth's shape • Describe how scientists’ understanding of the Earth’s shape has evolved throughout history
• Describe the contributions of key individuals (e.g., Eratosthenes, Newton, Picard, Bouguer, LaPlace, La Candamine) to scientists’ understanding of the Earth’s shape
• Explain how technological and mathematical advances have led to more sophisticated knowledge about the Earth’s shape
• Describe and critique early efforts to measure the Earth’s size and shape
##### DM-44 - Approximating the Earth's shape with geoids • Explain why gravity varies over the Earth’s surface
• Explain how geoids are modeled
• Explain the role that the U.S. National Geodetic Survey plays in maintaining and developing geoid models
• Explain the concept of an equipotential gravity surface (i.e., a geoid)
##### DM-43 - Approximating the geoid with spheres and ellipsoids • Identify the parameters used to define an ellipsoid
• Differentiate the Clarke 1866 and WGS 84 ellipsoids in terms of ellipsoid parameters
• Differentiate between a bi-axial and tri-axial ellipsoid and their applications
• Explain why spheres and ellipsoids are used to approximate geoids
• Distinguish between a geoid, an ellipsoid, a sphere, and the terrain surface
• Describe an application for which it is acceptable to use a sphere rather than an ellipsoid