HARMONIC ANALYSIS OF THE GRAVITY TIDAL DATA OBSERVED AT THE SHANGHAI STATION FROM APRIL TO AUGUST, 1978

The shanghai gravity tidal station is located at =31.1°N, =112.2°E, using a gravimeter type GS-15 No. 227 installed in a tunnel. The annual mean temperature in the tunnel is 18.8℃, the annual deviation of which is 0.3℃. The scale value of the gravimeter is 2.99 gal/mm. The data continuously observed from April to August in 1978 (142 days) were analysed by both the methods of Lecolazet and Venedikov. The results of analysis by the method of Lecolazet are as follows: δ(M₂)= 1.142, δ(K₁)= 1.164, δ(O₁)= 1.192, δ(O₁)-(K₁)= 0.028, while that by the method of Venedikav are:  δ(M₂)=1.142, δ(K₁)=1.166, δ(O₁)=1.189, δ(O₁)-δ(K₁)=0.023. Besides, the accuracy of methods of Lecolazet and Venedikov were tested on the electronic computer DJS-18 of the Peking university. The test results are as follows:(1) For method of Lecolazet, the accuracy of determination of gravimetric factor δ of the main waves M₂, S₂, N₂, K₁, O₁, is about 1%, while the accuracy of determination of the phase difference of the same main wave is about 1.(2) For method of Venedikov, the accuracy of analysis depends on the length of the observational data, in general the longer the data, the more accurate the result. When the length of the data is 90 days, the accuracy of determination of the gravimetric factor δ  of the main waves M₂, S₂, N₂, K₁, O₁ is about 1% the accuracy of determination of phase difference of the same main wave is about 0.5°.