The Computation of Geoidal Undulation Deflection of Vertical and Gravity Anomalies Using Clenshaw Summation

In the pysical geodesy,spherical harmonic series are frequently used to compute geoidal undulation,deflection of vertical and gravity anomalies.However if the Clen-shaw summation were used,the computation could be made more convenient. Some comparisons have been made between the initially developed models A and B in our country and Rapp model,by 5°×5°mean geoidal undulation and deflection of vertical,covering an area of 80°-120°east longitude and 20°-40°north latitude.Each model has been truncated up to 22 degree and order.The comparison of mean gravity anomalies has been made between observational and each one of three models. The results show that:(1)ΔN_A,the difference of geoidal undulations between A model and Rapp model,has a systematic tilt near east-west direction.ΔN_B,the dif-ference between B model and Rapp model,has a strong ascent in North-West China and a descend in North-West China.(2)Δξ_B,the difference of components ξ,between B model and Rapp model,has a descend in Central China,and Δη_A,the differnce of components η,between A model and Rapp model,has a systematic tilt.(3)The mean errors of the differences of mean gravity anomalies obtained by obsevations and each one of three models separately are similar. The conclusion is that A and B models are not more suitable than Rapp model for our country.