Abstract
In order to reduce the errors in numerical calculations of Laplacian and Jacobian, an attempt is made to extend the gridpoint system from 5 to 9 or 25 points. The truncation errors are divided into two kinds; one is symmetrical and the other orientational. The author asserts that in order to get high accuracy of calculation, not only the former error but also the latter must be reduced, which has been apt to be neglected. Taking some examples of patterns, numerical calculation schemes of Laplacian and Jacobian are tested by comparing the numerical with the analytical values.
