Figure 6.1 Conversion of a discontinuous land use distribution (A) into a continuous isarithmic surface (B) with regional trends (C) and locad residuals(D).Sample guarat of sobreiro woodland in the Tagus-Sado balmcentral Portugal, with contours of five-degree intervals and areas allow the mean sh ded. Source: Haggett, 1961b, p. 20.