Understanding Adjustment from an Information Theoretic Perspective
Objects:It is tried to understand the adjustment from an information theoretic viewpoint.Methods:Besides the concepts of covariance matrix,cofactor matrix and weight matrix,which are often in-troduced in"Surveying Adjustment"courses,we introduce the concept of Fisher information matrix(or simply information matrix)in this paper.Results:Several important properties of the information matrix are shown;the population and the sample information matrices are distinguished.The information matrix under the assumption of multivariate normal distribution is derived;the links among the population/sample infor-mation matrix,the population/sample covariance matrix and the cofactor/weight matrix are explained;and it is revealed that the weight matrix can be viewed as a normalized information matrix.Based on the infor-mation matrix,the concept of information vector is introduced;the adjustment in information domain is de-rived in which the information matrix and the information vector are calculated rather than the parameter vector and the covariance matrix calculated in standard adjustment.Though equivalent with the standard ad-justment in terms of the results,the information-domain adjustment has simpler format and clearer struc-ture;this provides a new perspective for understanding the traditional adjustment;more importantly the in-formation-domain method has special merits in solving under-determined model and also in initializing the recursive adjustment method.Finally,the dynamic adjustment in information domain is derived for filtering a dynamic state space model;it is nothing but the information filter whih is equivalent to the standard Kal-man filter.Conclusions:Information theory provides new insights for comprehensively and thoroughly un-derstanding the surveying adjustment theory.
indirect/parameter adjustmentFisher information matrixmultivariate normal distributioninformation vectorinformation-domain adjustmentinformation filtering