Gravimetric Network Research Articles

AN EVALUATION STUDY OF THE CORRECT COMPUTATIONAL APPROACH FOR THE CONVERSION OF GRAVIMETRIC DATA FROM ONE REFERENCE DATUM TO ANOTHER

Abstract The major deficiencies besetting most gravimetric networks as a result of non-adherence to the use of the correct computational approach for the conversion of the gravity data from one reference datum to another are discussed. In order to evaluate the computational models developed for the correct conversion, a typical gravity network was used as a case study. Field observations were carried out at the same sites as had been used initially in observing the typical gravity network. Observations were tied to the nearby standard gravity network so as to calibrate and monitor the behaviour of the gravimeter used for the survey. Analysis of the data shows that there are flaws in the original data set. Typical values of corrections required at each site to convert the network to the IGSN 71 standard using the GRS 67 are obtained. Some recommendations that will aid the proper harmonisation of gravimetric data are given. It is concluded that gravimetric work of reasonable size should always be referred t...

The establishment of the national gravity standard base net of Egypt (N.G.S.B.N.-77)

The earliest gravity measurements in Egypt were carried out by the Anglo-Egyptian Oil Company using Holweck-Lejay pendulum in the period 1937–1940. The measurement comprised few stations (about 41) in restricted areas along both the Western and Eastern coasts of the Gulf of Suez. During the period 1950–1951 Prof. G. Woolard made 21 gravimetric measurements in Egypt as a part of the world-wide gravity base net. Thi was refeered to Potsdam absolute value which was considered as the World Gravity Datum. In 1974, a new world-wide gravity net was published (I.G.S.N.71) which introduced a new concept for the world gravity reference datum, and consequently has replaced the Potsdam System. Since then, it was recommended that a national gravimetric network of base stations in Egypt on the basis of the I.G.S.N.-71 be established within the frame of establishing a gravity map of Egypt. In the period from January 1975, The General Petroleum Company carried out 624 gravity observations throughout the country. These measurements have been combined with the I.G.S.N.-71 values to form 65 gravity base points which in turn from the N.G.S.B.N. (Fig. 1).

Establishment of a Precise. Gravimetric Network in the Tokai District, Central Japan

Establishment of a Precise. Gravimetric Network in the Tokai District, Central Japan

THE USE OF THE GRAPHIC CHART FOR THE ANALYSIS OF OBSERVATIONS IN A GRAVIMETRIC NETWORK

AbstractThis paper presents a graphic chart designed for the analysis of observations in a gravimetric network. Features of observations which can be evaluated with the graphic chart are observational completeness, homogeneity and symmetry. The underlying theories of the evaluation are given and a test application of the chart is made using the data from the primary gravity network of Nigeria.

THE USE OF THE GRAPHIC CHART FOR THE ANALYSIS OF OBSERVATIONS IN A GRAVIMETRIC NETWORK

This paper presents a graphic chart designed for the analysis of observations in a gravimetric network. Features of observations which can be evaluated with the graphic chart are observational completeness, homogeneity and symmetry. The underlying theories of the evaluation are given and a test application of the chart is made using the data from the primary gravity network of Nigeria.

Structure of the inner core inferred from observations of its spheroidal shear modes

Spheroidal modes of elastic‐gravitational oscillation that have an energy partition dominated by shear energy in the inner core are called core modes. Recordings from the IDA gravimeter network of an earthquake in the Tonga region on June 22, 1977 have provided the first unambiguous observations of core modes. They conclusively show that, at low frequencies, the inner core has a very high Q (about 3500). They also tightly constrain the ratio of the inner core radius to the mean shear velocity to be 345s with an uncertainty of 0.5%.

The Equiprobable Interval Method of Sample Classification and the Validity of the χ2 Test

The equiprobable interval method of sample classification is examined and applied to a large sample of residuals from a gravimeter network adjustment. This method seems to possess several advantages over the commonly used constant interval method insofar as the validity of the χ2 test is concerned.

Report on the gravimetric measurements in the basic gravimetric network during 1950

The report gives a brief review of gravimetric work carried out in 1950 by the former State Institute of Geophysics (now the Central Institute of Physics) in cooperation with the State Geodetic and Cartographic Institute in the basic gravimetric network of 1st and 2nd order on the territory of Czechoslovakia.

Report on gravimetric measurements carried out at points of the basic gravimetric net-work during 1948 and 1949 on the territory of Czechoslovakia

A survey of gravimetric work conducted during 1948 and 1949 over the basic gravimetric net-work of 1st and 2nd order on the territory of Czechoslovakia is given. The choice of the gravimetric points, the way of carrying out systematic gravimetric work of basic character and measurements on the gravimetric points are described. Further the joining of the basic network to the pendulum stations, the measurement of the vertical gradient of gravity and other detailed measurements together with various checks on the Norgaard gravimeter used are also described.