  In this paper, the evolution of a polygonal spiral curve by the crystalline
curvature flow with a pinned center is considered with two view points,
discrete model consist of an ODE system of facet lengths and a level set
method. We investigate the difference of these models numerically by
calculating the area of the region enclosed by these spiral curves. The area
difference is calculated by the normalized L1 norm of the difference of
step-like functions which are branches of arg(x) whose discontinuities are only
on the spirals. We find the differences of the numerical results considered in
this paper are very small even though the evolution laws of these models around
the center and the farthest facet are slightly different.
