Yang et al. [8] argue that small (in area) elements are needed in image region where the second directional directive is large and have introduced the error diffusion (ED) scheme.
So, the eigenvalues of the Hessian matrix are exactly the two extreme of u α ″ and the corresponding eigenvectors are the directions along which the second directional derivative reaches its extreme.
The formulae for the second directional derivative of the curvature in the isophote direction and its gradient direction are thus begin{array}rcl@ K_{zetazeta} = frac{-2K_{x}K_{xy}K_{y} + K_{xx}{K_{y}^{2}}+{K_{x}^{2}}K_{yy}}{{K_{x}^{2}}+{K_{y}^{2}}} end{array} (7).
Now using the isophote orientation vectors (f i s o,x,f i s o,y ) at each pixel, we obtain the following noise-resistant approximation of the second directional derivative of the curvature in the isophote direction K_{zetazeta} approx f^{2}_{iso,x}K_{xx} + 2f_{iso,x}f_{iso,y}K_{xy} + f^{2}_{iso,y}K_{yy} (11).
The values of the second directional derivatives of the curvature in its isophote and gradient directions can be computed without actually calculating the isophote and gradient angles.
Posted near the city airport, the Confederate Boulevard markers were the first directional signs many visitors to Little Rock encountered.
Note, though, that street names (on street signs, for example) do not include the first directional component, although some maps do.
This summed signal is then fed through a LNA and a LPF and finally reaches the second directional coupler.
Both leakage and compensation signals were routed to the front end of our RFID receiver [27] where they combine in the first directional coupler.
Second, directional and background reflectance effects, induced by the interactions between the sun-sensor geometry and the observed canopy surface, make up-scaling of empirically derived relationships between changes in spectral reflectance and vegetation conditions difficult.
