ANGLE REDUCTION ANDMERIDIAN CONVERGENCE

Learning Objectives

After this lecture you will be able to:

Reduce measured angles for geodetic calculations

Apply meridian convergence

Lecture Outline

SP1 Reducing observed angles to spheroid Diagrams Meridian Convergence Geodetic Traverses Conclusion

SP1 Requirements In Study Book

Reduction of Measured Angles to the Spheroid Deflection of Verticals Correction

– Geoid and ellipsoid normals different Skew Normals Correction

– Normals at each end not parallel– Correct to eliminate effect of two normal

sections Laplace Correction

– Relationship between astronomical observed and geodetic azimuths

– Used to correct astronomical azimuths

Sample Data

We will cover these in next Prac/Tutorial Indicative order of magnitude

– Deflection correction 0”.063– Skew normal correction 0”.003– Laplace correction -6”0.72

Diagrams

Diagrams

Meridian Convergence

Geodetic Traverse - Several Diagrams

Usual Diagram

Another way of depicting the same diagram is:

Geodetic Traverse - Single Diagram

Meridian Convergence - ()

Meridian Convergence - ()

Meridian Convergence - ()

Summary

We investigated: SP1 requirements Corrections for

– Deflection of Verticals– Skew Normals– Laplace Corrections

Meridian Convergence Geodetic diagrams

Conclusion

You can now:

Reduce measured angles to a form in which they can be used for geodetic calculations

Calculate and apply meridian convergence

Self Study

Read relevant module in study materials

Review Questions