  We examine the effectiveness of the ground-plane invisibility cloak generated
from quasiconformal mapping of electromagnetic space. This cloak without
anisotropy will generally lead to a lateral shift of the scattered wave, whose
value is comparable to the height of the cloaked object, making the object
detectable. This can be explained by the fact that the corresponding virtual
space is thinner and wider than it should be. Ray tracing on a concrete model
shows that for a bump with a maximum height of 0.2 units to be hidden, the
lateral shift of a ray with 45 degree incidence is around 0.15 units.
