bundle block adjustment with 3d natural cubic splines

bundle block adjustment with 3d natural cubic splines bundle block adjustment with 3d natural cubic splines

13.07.2015 Views

The extended collinearity equations are a mathematical model for bundle blockadjustment.The mathematical model of bundle block adjustment consists of twomodels, a functional model and a stochastic model. The functional model representsgeometrical properties and the stochastic model describes statistical properties. Therepeated measurements at the same location in the image space are represented withrespect to the functional model and the redundant observations of image locationsin the image space are expressed with respect to the stochastic model. While theGauss-Markov model uses indirect observations, condition equations such as coordinatetransformations, and the coplanarity condition can be employed in the adjustment.The Gauss-Markov model and the condition equation can be combined intothe Gauss-Helmert model. In addition, functional constraints such as points havingthe same height or straight railroad segments can be added into the block adjustment.The difference between condition equations and constraint equations is that conditionequations consist of observations and parameters, and constraint equationsconsist of only parameters. With the advances of technology, the input data in photogrammetryhas been increased so adequate formulation of adjustment is required.All variables are involved in the mathematical equations and the weight matrix ofvariables is changed from zero to infinity depending on variances. Variables with thenear to zero weight are considered as unknown parameters and variables with thenear to infinite weight are considered as constants. Most actual observations are inexistence between two boundary cases. Assessment of adjustment, post-adjustmentanalysis, is important in photogrammetry to analyze the results. One of the assessmentmethods is to compare the estimated variance with the two-tailed confidence66

interval based on the normal distribution. The two-tailed confidence interval is computedby a reference variance σ 2 o with χ 2 distribution asr̂σ 2 oχ 2 r,α/2< σ 2 o < r̂σ2 oχ 2 r,1−α/2(4.6)where r is degrees of freedom and α is a confidence coefficient (or a confidence level).If σo 2 has the value outside of the interval, we can assume the mathematical modelof adjustment is incorrect such as the wrong formulation, the wrong linearization,blunders or systematic errors.4.3 Pose estimation with ICP algorithmUnlike the previous case with spline segments which the correspondence betweenspline segments in the image and the object space are assumed, now it is unknownwhich image points belong to which spline segment. ICP algorithm can be utilized forthe recovery of EOPs since the initial estimated parameters of the relative pose canbe obtained from orientation data in general photogrammetric tasks. The originalICP algorithm steps are as follows. The closest point operators search the associatepoint by the nearest neighboring algorithm and then the transformation parametersare estimated using mean square cost function.The point is transformed by theestimated parameters and this step is iteratively established until converging into alocal minimum of the mean square distance. The transformation including translationand rotation between two clouds of points is estimated iteratively converging into aglobal minimum. In other words, the iterative calculation of the mean square errorsis terminated when a local minimum falls below a predefined threshold. The smallerglobal minimum or the fluctuated curve requires more memory intensive and timeconsuming computation. In every iteration step, a local minimum is calculated with67

The extended collinearity equations are a mathematical model for <strong>bundle</strong> <strong>block</strong><strong>adjustment</strong>.The mathematical model of <strong>bundle</strong> <strong>block</strong> <strong>adjustment</strong> consists of twomodels, a functional model and a stochastic model. The functional model representsgeometrical properties and the stochastic model describes statistical properties. Therepeated measurements at the same location in the image space are represented <strong>with</strong>respect to the functional model and the redundant observations of image locationsin the image space are expressed <strong>with</strong> respect to the stochastic model. While theGauss-Markov model uses indirect observations, condition equations such as coordinatetransformations, and the coplanarity condition can be employed in the <strong>adjustment</strong>.The Gauss-Markov model and the condition equation can be combined intothe Gauss-Helmert model. In addition, functional constraints such as points havingthe same height or straight railroad segments can be added into the <strong>block</strong> <strong>adjustment</strong>.The difference between condition equations and constraint equations is that conditionequations consist of observations and parameters, and constraint equationsconsist of only parameters. With the advances of technology, the input data in photogrammetryhas been increased so adequate formulation of <strong>adjustment</strong> is required.All variables are involved in the mathematical equations and the weight matrix ofvariables is changed from zero to infinity depending on variances. Variables <strong>with</strong> thenear to zero weight are considered as unknown parameters and variables <strong>with</strong> thenear to infinite weight are considered as constants. Most actual observations are inexistence between two boundary cases. Assessment of <strong>adjustment</strong>, post-<strong>adjustment</strong>analysis, is important in photogrammetry to analyze the results. One of the assessmentmethods is to compare the estimated variance <strong>with</strong> the two-tailed confidence66

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