Lecture 9 - Geodetic Calculations on the Ellipsoid

Question 1

What is ellipsoidal geodesy?

Answer 1

Part of geometric geodesy which is concerned withe describing locations in terms of geometry - the study of coordinate systems and angular and linear relationships of geodesic curves on ellipsoids of rotation which best approximate the shape of the whole planet or parts thereof (these mathematically defined surfaces are datums)

Question 2

Why does one need a reference ellipsoid in geodesy?

Answer 2

For calculations on the Earth’s ellipsoid.

Question 3

What are the basic elements of a reference ellipsoid?

Answer 3

Semi-major axis, inverse flattening, angular velocity, geocentric gravitational constant.

Question 4

What are two normal sections whose curvatures are maximum and minimum?

Answer 4

Meridian section, prime vertical section.

Question 5

What is geodesic?

Answer 5

The shortest line between two points on the Earth’s ellipsoid.

Question 6

Why do we need to perform measurement reductions?

Answer 6

Part of preliminary processing. The quality of a control network relies on the quality of measurements inclusive of the quality of their reduction.

Question 7

What are the three basic requirements in terms of measurement reductions?

Answer 7

Plumbline-aligned (normal aligned)

Geometrically ground based (H does not equal 0)

Geometrically normal aligned (geodesic aligned)

Question 8

What is deflection of vertical?

Answer 8

Deflection of the plumb line, a measure of how far the direction of the local gravity field has been shifted by local anomalies such as nearby mountains or underground irregularities.

The angle between the true zenith and the line perpendicular to the surface of the reference ellipsoid.

Question 9

What is the ellipsoid?

Answer 9

A surface of revolution created by rotating an ellipse about its minor axis.

Question 10

What are the curvilinear coordinates?

Answer 10

Latitude, B

Longitude, L

Altitude, H

Question 11

What are the meridian plane coordinates?

Answer 11

Assuming a meridian plane with the longitude, L

L, x, y

Question 12

What are cartesian coordinates?

Answer 12

x, y, z

Question 13

What is a normal section?

Answer 13

A curve on the ellipsoid cut by the normal plane. The radius of curvature of a normal section depends on the azimuth of the normal plane.