**diffx**- numerical aproximation to first derivative of TOS in x using (-1,0,1) filter.**diffy**- numerical approximation to first derivative of TOS in y.**grdsq**- sum squared of diffx and diffy of TOS image.**lap**- sum of the second derivatives in x and y of TOS image.**ddn**- second order image derivative invariant of TOS image.**ddt**- second order image derivative invariant of TOS image.**crv**- curvature of TOS image with IP(Precision).

root 2017-11-23