Because the model is fitted internally, i.e., using the terrestrial sample 𝑠2s2 of the inventory area, this leads to the important zero mean residual property of the theoretical model residuals over the inventory domain F, i.e., ∫𝐹𝑅𝑐(𝑥)𝑑𝑥∫FRc(x)dx. Mandallaz [30]...