  For a spatiotemporal process $\{X_j(s,t) | ~s \in S~,~t \in T \}_{j =1,
\ldots , n} $, where $S$ denotes the set of spatial locations and $T$ the time
domain, we consider the problem of testing for a change in the sequence of mean
functions. In contrast to most of the literature we are not interested in
arbitrarily small changes, but only in changes with a norm exceeding a given
threshold. Asymptotically distribution free tests are proposed, which do not
require the estimation of the long-run spatiotemporal covariance structure. In
particular we consider a fully functional approach and a test based on the
cumulative sum paradigm, investigate the large sample properties of the
corresponding test statistics and study their finite sample properties by means
of simulation study.
