ANGLE REDUCTION AND MERIDIAN 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 – Skew normal correction – Laplace correction 0”.063

0”.003

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 - (

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Meridian Convergence - (

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Meridian Convergence - (

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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