1985 Vol. 10, No. 4
It is an important mission of Geodesy to improve an accuracy of control networks and to establish the geocentric coordinate system via combined satellite and terrestrial network adjustment.This paper discusses various approches for performing the combined adjusment in three-dimensional rectangular coordinate system,based on the results of separate adjustment of the two types of networks,and proposes the relevant models for transformation.
This paper lays emphasis upon reference datum of dynmic geodetic network.Included in this paper are the discussion of the relation between the adjustment of free network and reference datum,the derivation of a general estimation formula of the coordinate parameters of arbitrary reference datum of free network,and the derivation of the transformation formula of the coordinate parameters and its cofactor matrix from the theory of reference datum.In addition,a procedure for analysis of displacement has been proposed,a practical example has been illustrated and the influence of different reference datum to the solution of displacement has been explained.
In order to calculat the accuracy of high precision traverse,several schemes have been adopted in this paper.As a result of these calculations,three methods for increasing the accuracy of high precision traverse are analyzed and two best schemes for establishing high precision traverse in China are recommended.
With problems in geodesy and surveying,if the position of stations can be determined many,many times and adjusted by the sequential method,the results can be proved to be the same as with Kalman filter.In fact,with such problems sequential adjustment and Kalman filter can be proved to be one the same thing.Since in the short-arc Doppler satellite positioning computations,the positions of the satellites and ground points are all considered known only approximately,and corrections to these unknowns are sought,thus they are in nature same as the so-called "Free network adjustment",the problem can be solved by first making the sum of the squares of the observed residuals minimum and then make the sum of the squares of the corrections to the unknowns(corrections to its ground points) minimum.Since the minimum requirements are made one after another,the auther suggests this method may be called the method of separate minimization.This method has been discussed by many geodetists of the world.With Doppler satellite positioning adjustments,we can solve this problem by requiring the sum of the residuals of observations and the sum of squares of the corrections to the approximate initial Positions of the stations minimum at the same time.This method,the auther calls the method of sum minimization.Viewed from the theory of Kalman filter,the method of semishort-arc sum-minimization is uniformally completely controlable.And it is proaved in this paper it is also uniformally completely observable.Then from the theory of Kalman filter,the solutions in this case,the position of the ground points are uniformally asymtotic stable.That is,however large the error of the approximate initial points may be,when the number of times of observing the NNSS passes are large enough,the erronous initial points will converge to the theoretical best estimate,i.e.best point positions.An obvious reason for this,in the case of single point determination using Doppler satellites,many,as much as 50 or 100 of satellite passes are observed.The random errors would be eliminated mostly,and the result will converge to the theoretical best points.
This paper deals with the following problems,1)The necessity of taking the influence of initial datum error into account when estimating the accuracy of a control network.2)Is it necessary to reestablish the principal network when its accuracy is lower than that of the secondary one?For the first problem five examples have been given to show the importance and to negate the traiditional requirment that the influence of the initial datum error must be much less than that of the observation error,when establishing a control network.As for the second problem,two measures have been proposed,i.e.to compensate low accuracy of the principal network by high accuracy of the secondary one and to change the configuration of the network using an appropriate observation accuracy.It is believed that the reestablishment of the principal network can be avoided.
This paper deals with the mathematical structure of adjustment computations and is rather an introductory treatise.It is divided into four sections.The first section mainly introduces the nature of some spaces in adjustments.The second section discusses the classification problem of adjustment models.The third section is the focal point in this paper and describes how to use the commutative diagram to write down the main formulas of adjustment directly,the concepts of the two preceding sections being used here.In the last section of this paper some complementary related problems are discussed.
The method introduced in this paper may be used for determining simultaneously the wobbling error of a vertical axis and the sensibility of a tubular level by the automatic vertical index of a theodolite.This method is also suitable for the theodolite with a contract index level.
In order to obtain a high quality objective or optical system,it is of vital importance in theory and practice of the optical design that the designing results should satisfy the evaluator of the image quality accorded with the use requirements.In this paper,several objectives and optical systems designed by the anther and manufactured since 1978 are taken as the examples to discuss the adaptation between image quality and the receiver;the scheme of the optimal equilibrium of abberations and the principle of comprehensive consideration for the individual abberation.The designing results and their evaluation of the above-mentioned objectives and optical systems are cited.
In this paper the motion differential equations,transfer functions and frequency characteristics of the tracking follower system of G171 Satellite Laser ranger are analyzed and calculated.It also analyzes the linearity and dead band of the system.On the basis of these analyses,it indicates that theoretic and measuring values of the system's dynamic quality index are well consistent,and the system's steadiness and briskness are fine.
This paper introduces and justifies the evaluation of classification using the normal distribution model which is the most fundamental one in the probability distribution functions.Then it puts forward the design method of classifying map content using the principle of normal distribution.In a concrete example,the author adopted two control areas in the course of design and dealt with the non-equal intervals the way for the equal intervals to make it more widely applicable.Finally taking the x2 distribution function as an example,the author further suggested a designing method of classification using other distribution functions to meet the needs of some special classification needs.
The cloud distribution in the atmosphere is an important basis for the weather forecast.This paper discusses the probability of analysing the cloud distribution utilizing the satellite cloud picture,and gives the method for tracing the cloud contours.Finally,some experimental results are presented.
In this paper,the forward,backward and intermediate difference formulae of the function F(x,y) are given.It points out:one argument equal step difference formula is a special example of the mapping difference and the mapping difference is obtained by one argument difference by mapping .By the use of these formulae the approximate evaluation of points in a plane stoping line can be solved.