The domain considered is [0,1] x [0,1], and an IDE is simulated on top of a fixed effect comprising of an intercept, a linear horizontal effect, and a linear vertical effect (all with coefficients 0.2). The measurement-error variance and the variance of the additive disturbance are both 0.0001. When a spatially-invariant kernel is used, the following parameters are fixed: \(\theta_{p,1} = 150\), \(\theta_{p,2} = 0.002\), \(\theta_{p,3} = -0.1\), and \(\theta_{p,4} = 0.1\). See IDE
for details on these parameters. When a spatially-varying kernel is used, \(\theta_{p,1} = 200\), \(\theta_{p,2} = 0.002\), and \(\theta_{p,3}(s), \theta_{p,4}(s)\) are smooth spatial functions simulated on the domain.