1. ANGLE REDUCTION AND MERIDIAN CONVERGENCE

2. Learning Objectives After this lecture you will be able to: n Reduce measured angles for geodetic calculations n Apply meridian convergence

3. Lecture Outline n SP1 n Reducing observed angles to spheroid n Diagrams n Meridian Convergence n Geodetic Traverses n Conclusion

4. SP1 Requirements n In Study Book

5. Reduction of Measured Angles to the Spheroid n Deflection of Verticals Correction –Geoid and ellipsoid normals different n Skew Normals Correction –Normals at each end not parallel –Correct to eliminate effect of two normal sections n Laplace Correction –Relationship between astronomical observed and geodetic azimuths –Used to correct astronomical azimuths

6. Sample Data n We will cover these in next Prac/Tutorial n Indicative order of magnitude –Deflection correction0”.063 –Skew normal correction0”.003 –Laplace correction-6”0.72

7. Diagrams

9. Meridian Convergence

10. Geodetic Traverse - Several Diagrams

11. Usual Diagram Another way of depicting the same diagram is:

12. Geodetic Traverse - Single Diagram

13. Meridian Convergence - (  )

16. Summary We investigated: n SP1 requirements n Corrections for –Deflection of Verticals –Skew Normals –Laplace Corrections n Meridian Convergence n Geodetic diagrams

17. Conclusion You can now: n Reduce measured angles to a form in which they can be used for geodetic calculations n Calculate and apply meridian convergence

18. Self Study n Read relevant module in study materials

19. Review Questions