1. The physical surface of the earth is called the _________.

2. The term, __________, describes gravity on the earth’s measured surface.

3. The mathematical approximation of the surface of the earth is called an _____________.

4. Geoid measurements are found via _________ ___________ (gravimeters) or from measurements of ____________ (ephemerides.)

5. The ellipsoid approximation is a required element of any ______________ system.

6. In modern geodesy, the measurement of the earth’s perameters always begins at it’s _______.

7. Name the four most important perameters of the earth: • _____________________ • _____________________ • _____________________ • _____________________

8. The oldest ellipsoid is __________ _______, which works well for only North America.

9. The two very similar ellipsoid systems that are most commonly used today are _______ _______ and _______ _______.

10. The difference between the geoid and ellipsoid height is calcuated by subtracting the ___________(h) height from the ____________(H) height (N=h-H.)

Answer Key:

1. Terrain

2. Geoid

3. Ellipsoid

4. Surface Instruments, Satellites

5. Coordinate

6. Center

7. Semi-Minor Semi-Major Flattening Eccentricity Squared

8. Clark 1866 (’66)

9. GRS 1980, WGS 1984

10. Geodetic, Orthometric

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