bundle block adjustment with 3d natural cubic splines

Hessian. Interest point operators which detect well-defined point, edges and cornersplay an important role in automated triangulation and stereo matching. For example,the Harris operator is defined as a measurement of corner strength asH(x, y) = det(M) − α(trace(M)) 2 (2.1)where M is the local structure matrix and α is a parameter so that H ≥ if 0 ≤ α ≤0.25. A default value is 0.04. The gradients of x and y direction areg x = ∂I∂x ,g y = ∂I∂y(2.2)with I is an image. The local structure matrix M isM =with A = gx, 2 B = gy, 2 and C = g x g y .A corner is detected when[A CC B](2.3)H(x, y) > H thr (2.4)where H thr is the threshold parameter on corner strength.The Harris operator searches points where variations in two orthogonal directions arelarge using the local auto-correlation function and providing good repeatability undervarying rotation, scale, and illumination. Förstner corner detector is also based onthe covariance matrix for the gradient at a target point.A preliminary weight iscomputed asw pre ={ det(M), trace(M)p > p thr0, otherwise(2.5)11