  We compare the behaviour of a small truncated coupled map lattice with random
inputs at the boundaries with that of a large deterministic lattice essentially
at the thermodynamic limit. We find exponential convergence for the probability
density, predictability, power spectrum, and two-point correlation with
increasing truncated lattice size. This suggests that spatio-temporal embedding
techniques using local observations cannot detect the presence of spatial
extent in such systems and hence they may equally well be modelled by a local
low dimensional stochastically driven system.
