1990 Vol. 15, No. 4
The quality characteristics(accuracy,relialility and separalility) of combined adjustment with photogrammetric and geodetic observations are throughout studied with simulated data.A scheme for the practical design of the comlined network is suggested.The investigation is beneficial to the practical applicataon and the intelligent realization of combined adjustment.
The modulation frequency and additive constant of an electronic tacheometer Wild Tachymat TC 1600 were tested versus temperature and supply voltage.The differences between measured and predicted frequencies did vary by only ±1.4 Hz(or±0.1ppm) from the average difference across the entire temperature range from-10℃ to +50℃.Thevariation of the additive constant over the same temperature range was very small(±0.23mm) and statistically insignificant.No significant effects of supply voltage on frequency and additive constant were found.In addition,the additive constant was tested versus signal strength.Changes of 1 mm maximum were found at very low signal strengths creating scale errors of less than 0.5ppm under field conditions.When establishing the frequency-versus-temperature characteristic,full use was made of the accessibility of internally measured temperatures and internally computed predicted frequencies.Internal temperatures differ between 0 and +11.5℃ from ambient temperatures,depending on length of operation,previous temperature exposure and present temperature.The warm-up effects on the difference frequency and the additive constant were also insignificant with 0.2ppm per 30 min.and 0.24mm per 100 min.,respectively.A standard deviation of a single TC 1600 distance observation("DIST" mode) of±0.5mm was found during laboratory tests.On an EDM calibration baseline,average standard deviations of(±0.4mm+0.4ppm) were realized for means of 4 to 8 distance measurements.Short periodic errors were found to change with distance but did not exceed 1 mm amplitude.
There are still two problems unsolved in the precise gravity networks:One is how to weight various observations;the other is how to cancal the unecessary parameters of the retative gravity meters.It is discussed in this paper to define the weights of various observations by use of vaviance component estimation and to select the additional parametrers by use of several kinds of hypothesis test.Through computation,comparision and analysis,some results have been obtained.
In the synthesis assessment of urban environmental qualities,there are a lot of factors impacting urban enviromental qualities.Each of them might play the defferent roles in the defferent layers.Generally,the relationship among them always is fuzzy.It is difficult to get a absolute result using general mathematics and even more difficult to compare the environmental qualities among several cities.In this paper,the mathematical model for multilayer fuzzy comprehensive judgements is applied to the synthesis assessment of urban environmental qualitie sin several layers.The result reflects the environmental qualities of defferent urbans in the subordinate level.
In this paper,various formulation of multibody space-time geodetic boundary value problems are presented,and the solutions to them are derived by taking spherical approximation and neglnecting topographic effects.Some discussions are made to these Solutions,which take some known solutions as special cases.
The paper has evaluated the relationships among three terrain reduction procedures(terrain correction,isostatic reduction,residual terrain reduction(RTM) and given the methods of their data processing.The emphasis has been laid to speed the computation and deal with the singular integration properly.Our major conclusions are as follows:——To the near zone of the computated point,or the'innermost zone',the terrain heights have a critical effect on the terrain reduction results,and the discrete integration need to be done particularly.The(terrain) height data in the innermost zone must be densified to decrease discrete error,the best method is bicubic spline function.——It is necessary to obtain detailed terrain height data in the innermost zone.(generally speaking,within 10~50km radius is enough).——It is highly important to consider the speed of computation.If there are many terain reduction points to be computated and the points are regular arranged,FFT algorithm is effective to save computer time.
This paper described the principle that made use of the microcomputer controlling teckniques for detecting starch level,real-time processing data and providing starch automaticallz.Then we presented the implementation techniques.
The design matrix may be a rank-defect matrix and the co-variance matrix of the observations may be the singular matrix,this generalized Gauss-Markov model is a uniformity model with simple form.Based on the principle of the Least-square estimation VTQ-V=min,this paper deals with the parameter estimation theory and method of the generalized G-M Model,explaines the coincidency of various adyustment rules such as VTQ-V=min and Rao and Bjeharmmar's.The paper discusses also the solution of the generalized G-M model and its charecters.
In this paper,we study the relation ships between the exereme stability of a giren differential equation and its limiting eqnations.Especially,we prove that,under some reasonable assumptions,the uniform x-asymptotin stability with respect to(H*,H) of a giren olifferential equation is implied by the similar stability of its limiting equaions.
A method for fast chosing optimal additional observations was advanced,in accordance with digital analysing results of the precision of areal geodetic networks.In terms of this method,the analytical simulation method was sucessfully applied to optimal design and improvement of middle large-scale areal geodetic networks.