We show both experimentally and theoretically that the sampling-induce
d hidden cycles can exist in scale-invariant rough surfaces having a c
orrelation length xi. If the sampling size L is sufficiently large, th
e oscillatory behavior will diminish with the fluctuation within an or
der of (xi/L)(d/2). This is consistent with the law of large numbers f
or the correlated systems: the average of N-correlated variables havin
g a correlation length xi will converge to their mean within an order
of root xi(d)/N. Based on this result, we propose that in order to dis
tinguish the mound surface from the self-affine surface, the sampling
condition root xi(d)/N much less than 1 and an average of a large numb
er of images are required.