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

Generally the larger noise level the more accurate approximations are required toachieve the ultimate convergence of the results. The worst case scenario for estimatingis that the large noise level leads the proposed model not to converge into thespecific estimates since the convergence radius is proportional to the noise level. Theparameter estimation is sensitive to the noise of the image measurement. Error propagationrelated with the noise error in the image space observation is one of the mostimportant elements in the estimation theory. The proposed bundle block adjustmentcan be evaluated statistically using the variances and the covariances of parameterssince a small variance represents that the estimated values have a small range anda large variance means that the estimated values are not calculated properly. Therange of the parameter variance is from zero in case of error free parameters to infinitein case of completely unknown parameters. The result of one spline segmentis expressed as table 5.4 with ξ 0 the initial values and ˆξ the estimates. The estimatedspline and spline location parameters along with their standard deviations areestablished without the knowledge of the point-to-point correspondence.If no random noise is added to image points, the estimates are converged to thetrue values. The quality of initial estimates is important in least squares system sinceit determines the iteration number of the system and the accuracy of the convergence.The assumption is that two points on one spline segment are measured ineach image so the total number of equations are 2 × 6(the number of images)×2(thenumber of points) +6(the number of the arc-length) and the total number of unknownsare 12(the number of spline parameters)+12(the number of spline locationparameters).The redundancy (= the number of equations - the number of parameters),the degrees of freedom, is 6. While some of geometric constraints such as80

Spline location parametersImage 1 Image 2 Image 3t 1 t 7 t 2 t 8 t 3 t 9ξ 0 0.02 0.33 0.09 0.41 0.16 0.47ˆξ 0.0415 0.3651 0.0917 0.4158 0.1412 0.4617±0.0046 ±0.0016 ±0.0017 ±0.0032 ±0.0043 ±0.0135Image 4 Image 5 Image 6t 4 t 10 t 5 t 11 t 6 t 12ξ 0 0.18 0.51 0.28 0.52 0.33 0.57ˆξ 0.2174 0.4974 0.2647 0.5472 0.3133 0.6157±0.0098 ±0.0079 ±0.0817 ±0.0317 ±0.0127 ±0.1115Spline parametersa 10 a 11 a 12 a 13 b 10 b 11ξ 0 3322.17 72.16 -45.14 27.15 4377.33 69.91ˆξ 3335.0080 70.4660 -48.8529 16.5634 4343.0712 63.0211±0.0004 ±0.0585 ±0.8310 ±1.2083 ±0.0004 ±0.0258b 12 b 13 c 10 c 11 c 12 c 13ξ 0 -17.49 13.68 48.82 10.15 -27.63 21.90ˆξ -28.7770 9.8893 51.9897 8.1009 -39.3702 13.3904±0.2193 ±0.2067 ±0.0006 ±0.0589 ±0.7139 ±1.0103Table 5.4: Spline parameter and spline location parameter recovery81

Generally the larger noise level the more accurate approximations are required toachieve the ultimate convergence of the results. The worst case scenario for estimatingis that the large noise level leads the proposed model not to converge into thespecific estimates since the convergence radius is proportional to the noise level. Theparameter estimation is sensitive to the noise of the image measurement. Error propagationrelated <strong>with</strong> the noise error in the image space observation is one of the mostimportant elements in the estimation theory. The proposed <strong>bundle</strong> <strong>block</strong> <strong>adjustment</strong>can be evaluated statistically using the variances and the covariances of parameterssince a small variance represents that the estimated values have a small range anda large variance means that the estimated values are not calculated properly. Therange of the parameter variance is from zero in case of error free parameters to infinitein case of completely unknown parameters. The result of one spline segmentis expressed as table 5.4 <strong>with</strong> ξ 0 the initial values and ˆξ the estimates. The estimatedspline and spline location parameters along <strong>with</strong> their standard deviations areestablished <strong>with</strong>out the knowledge of the point-to-point correspondence.If no random noise is added to image points, the estimates are converged to thetrue values. The quality of initial estimates is important in least squares system sinceit determines the iteration number of the system and the accuracy of the convergence.The assumption is that two points on one spline segment are measured ineach image so the total number of equations are 2 × 6(the number of images)×2(thenumber of points) +6(the number of the arc-length) and the total number of unknownsare 12(the number of spline parameters)+12(the number of spline locationparameters).The redundancy (= the number of equations - the number of parameters),the degrees of freedom, is 6. While some of geometric constraints such as80

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