FUNDAMENTAL SURVEYING Geodesy and Map Projections

Question 1

What shape best approximates the Earth for geodetic purposes?

Accepted Answer

An oblate spheroid (ellipsoid)

Answer

The Earth is best approximated as an oblate spheroid (ellipsoid of revolution), flattened at the poles and bulging at the equator.

Question 2

What is the geoid?

Accepted Answer

The equipotential surface of Earth's gravity field that approximates mean sea level

Answer

The geoid is the equipotential surface of Earth's gravity field that most closely corresponds to mean sea level.

Question 3

What is the difference between an orthometric height and an ellipsoid height?

Accepted Answer

Orthometric height is measured above the geoid; ellipsoid height is measured above the reference ellipsoid

Answer

Orthometric height (H) is measured above the geoid (mean sea level), while ellipsoid height (h) is measured above the reference ellipsoid; h = H + N (geoid undulation).

Question 4

What is the current official horizontal datum for the conterminous United States?

Accepted Answer

NAD83

Answer

NAD83 (North American Datum of 1983) is the official horizontal geodetic datum for the conterminous US.

Question 5

What is the current official vertical datum in the United States?

Accepted Answer

NAVD88

Answer

NAVD88 (North American Vertical Datum of 1988) is the official vertical datum for the US, replacing NGVD29.

FUNDAMENTAL SURVEYING Practice Test

FUNDAMENTAL SURVEYING Practice Test

FUNDAMENTAL SURVEYING Geodesy and Map Projections