1988 Vol. 13, No. 1
In this paper the author discusses the possibility of the improvement of the accuracy of the fictitious single layer density by collocation method using various kinds of gravity data. The uniquness of the solution is proved and the eovariance between the single layer density and the linear functionals of the disturbing potential are derived.In the second part of the paper, the computation of the single density and terrain correction by Fast Fourier Transform method is proposed. Simulating test shows that the FFT method is very fast and accurate.
This paper discusses the necessary and sufficient condition for the existence of a non-negative definite quadratic unbiased estimator (MINQE(U,NND)) of variance components, and explains theoretically why some negative estimators arise in MINQE (I,U) at times. From this conclusion variance components ma2 and mb2 of distance observations cannot be determined simultaneously and accurately by the MINQE in the direction-distance net adjustment. Furthermore, the analysis of some examples in the paper gives the same result. Therefore, considering the ease that ma2 is known generally, an improved variance component estimation model is provided for the direction-distance net adjustment, according to which we can obtain unbiased estimates of both direction and distance variance components and arrive at a reasonable solution to the above examples. In orther words, we can determine more appropriate and reasonable weights in the direction-distance net adjustment.
This paper puts emphasis on the measurement and the applications of MTF of the photographic system. Two filtering methods, i.e. the spatial domain filter and the speetral domain filter, have been compared and the result shows that the spectral domain filtering method is practical and effective. With regard to its, the paper proposes using the equivalent width of line spread function (EQW) as an image quality evaluating stan dard) the tests indicate that there is certainly similarity between 1/EQW and the resolution of the photograph. A tentative study of copy quality has also been made.
The least squares estimator, as an optimal estimator, has been widely used in the data processing of surveying science. Unfortunately the reliability of the least squares estimator may easily be destoryed by gross errors since its mathematic model is based on the prior assumption that errors of observations must be normally distributed. To avoid this problem, the robust estimator has been created and applied to various fields. The repeated median estimator (belongs to robust estimator family) has been studied in this article. An example of the transformation of coordinates between two systems using the repeated median was chosen to illustrate its principle and applications.
This paper starts its discussion from Lagrangian function expressed by different variables, and then it goes on to expounds and proves the uniformity of the two forms of Hamilton's principle for nonholonomic mechanical system. It also pats forward a re vision of the expression of Suslough's (Cycлов) form of Hamilton's principle for nonholonomic system and analyzes the nature of relevant controversies.
This paper puts forward the quick "table-seeking" principle and a set of methods for the electronic division of the Moré-fringe signal. The measurement accuracy is mainly dependent on the quality of the grating signal. The system can perform the real-time data sampling with fourty divisions of the Moré-fringe signal. The exeprimental results show that the "table-seeking" method can measure the grating displacement quickly and accurately.
This paper discusses the problem how mapping serves town planning and construction. Emphasis is placed on the selection of themes for maps to be used in town planning. The problem is approached from two different angles:the point and the area.
The paper deals with the effects on the adjusted results by using different adjustment models. Based on this theory, it gives a criterion of the selection and rejection of dynamic parameters:the smaller the estimator of unit weight variance factor σ02, the better the model. Then, by using the scan calculation technique, some unnecessary parameters are sifted out from the dynamic adjustment of leveling networks. In addition, the method have been applied to test calculation of leveling networks in some regioes. Compared with the former dynamic adjustment, the new method is more suitable to divide the points in the field into two kinds:stable points and dynamic points.
Based on the principle of the combination of the qualitative and quantitative determination, a system structure and a mathematical model for determination and evaluation engineering combining both fuzzy and precision aspeds has been developed by using the theory of fuzzy set and the method of statistic analysis. The determination and evaluation tests have shown that the system structure and its mathematical model can correctly represent the real situation with noticeable efficiency and its computation is both simple and rapid.
In this paper, the test method and the computation formula of eccentric errors in vertical axes series are briefly described, and the precision of the formula is discussed as well. This paper also presents the result of the calculation of the eccentric element (f) by means of the observed data and the mean value and variance are computed by using three method on the same instrument. Not only normal examination, gross error examination but also variance examination, are made with respect to measuring errors. Finally, while relevant data are analysed by way of variance, a comparison of the three methods is made with regard to their precision, and the applicability of each method is also analysed.