1980 Vol. 5, No. 2
This paper mainly deals with the principle of some methods of parameter estimation and analyses thier inner relationship.In addition the methods of modern adjustment of observation,including filtering,least squares collocation and Kalman filtering are described.
This paper tries to prove theoretically and practically that the current widely used mode of weighting in levelling nets adjustment is quite inappropriate.It requires more work done and reduces the efficiency of adjustment on the contrary.Basing on the mechanism of errors in levelling.a rigorous first derived for calculating the mean accidental error per kilometer η.And thence by the help of data of several repeating levellings,an analys is further made for the characteristic of the mean systematic error per kilometer σ.As σ is practically yet undeterminahle for the cuent levelling practice,cases of different modes of weighting with σ neglected are studied.The effect of these approximations of weighting on the efficiency of final adjustment is estimated and tested in actual examples.The result reveals that the currently used mode of weighting is the worst.Better ones are suggested.
Owing to the increasing use of laser alignment technique in engineering surveying,the problems of how to utilize it properly and to improve its precision have been raised.Further study of laser alignment is necessary.This paper deals with three major problems,the circular zone plate,the atmospheric effect and the detection of laser beam.Having derived the formulae to compute the intensity of the image formed by a circular zone plate,the author has come to the preliminary conclusion that a circular zone plate with 5-7 clear zones and opaque central zone is considered most suitable in practice and by properly designing zone plate,the number of the plates used on an aligned line can be minimized.Then atmospheric refraction and air turbulence causing random deflections are discussed in the paper,for they impose restrictions on alignment accuracy,The effect of atmospheric refraction is mathematically analyzed,some measures to reduce the effect are introduced and the design of the detector is discussed.
After a station adjustment according to the method of complete set of directions,a set of independent directions ought to be obtained.But because of lateral refraction and other kinds of systematic errors,directions in a station are really correlated.Using statistical theory and according to the charactoristics of error sources,we have obtained that the correlation coefficient between two directions is ρ=cos(i,j)/1+K,the rms of an angel is 0."55√1-1/1+Kcosα/1-1/2(1+K),here α is the value of the angle,and K is the ratio of random error and systimatic error.In China the average value of K is about 0.9.That is,the rms of an angle is dependent upon the value of the angle itself,larger angle having larger rms.In a traverse line,the angles all approximate to 180º,so their rms must be larger than those of a triangulation of the same class.Because of this kind of systematic error,the accuracy of the classical optical observation of traverse angles can hardly be improved.Lastly a model of correlated weight matrix is given,when we do the adjustment of an astro-geodetic network,we may take either angles or directions as independent elements,but they both have some degrees of approximation.
In a block adjustment by the method of polynomials,the author has adopted simulated photographs containing.respectively either systematic errors(affinity,parallelogram,trapezoidal,radial) or random errors(σ0=±10μm) or both.In the adjustment some typical block figures with different distribution of control points are employed.From the analyses of the result of the adjustment computation have been found:1) For the planimetric coordinate,the effect of systematic eliminated by adopting third order conformal polynomials errors can be efficiently eliminated by adopting third order conformal polynomials.2) As to the height adjustment,in order to eliminate the effect of systematic errors it is better to use the second order polynomials rather than the third order.3) The effect of systematic errors inside the block is greater than that around the block.
In this paper a new concept of working mode of the compensating function of an automatic level is introduced.After having investigated several kinds of typical and actual working mode,the author got a method of converting the above actual working mode into a fundamental one by an equivalent transformation.Through analysing two types of automatic levels Ni-007 and Ni-1,the author derived a formula respectively for computing the total amount of compensation and the geometrical condition of realizing the automatic levelling.
In this paper the author gives a method of dynamic allocation for the array storage of ALGOL compiler system for computer TQ-16 and also the direction for its use.Static allocation is usually adopted for the array storage of ALGOL compiler system for TQ-16.If we now use the dynamic allocation for the array storage,the internal storage will more efficiently be utilized.From the result of debugging and practice the expected aim and purpose can be achieved.For most practical programs,the real computing time does not increase evidently,while the compiling time reduces comparatively.
There are five methods of measuring land surface area on topographical maps.A paper  has made a detailed comparision between the complicateness of the various methods;it has,however,not indicated their internal relationships nor made a comparision between the results obtained by the various methods,as to what extent they approach the actual surface area.The author of the present paper attempts to prove by the fundamental formula of area and the principles of approximate calculation the mutual relationships between the various methods;accordingly,derives the non-equality between the values obtained by them and at the same time,compares their merits and defects according to their approximation to the actual area.Furthermore,the author makes a study by elementary method of the closeness of different asymmptotic numeral values to the actual area for ditffterent shapes of surface,which enables us to choose the most reasonable formulae of calculation in practice.Then,the author suggests a graphical method,based on the same principle of he above analysis,which simplifies the calculation work of the most accurate but more complicated Hua Lokeng and Wang Yuan s method.Lastly,based on the same principle,the anthor derives a set of new formulae,which are as accurate as the existed fomulae,but do not require the process of area on topographical maps.Hence they are especially useful in case of having no planimeter.