ABSTRACT
When we talk about error, everybody has an intuitive understanding of what is meant by it, but is it really clear? It is worthwhile to examine this matter more closely, and to define clearly what we mean by ‘error’. Here, error will be defined as the difference between reality and our representation of reality. Although this definition does not always make sense (for instance, there are huge irrelevant differences between a city and a city map, even when the map is ‘error-free’), it is appropriate for describing quantitative errors. For instance, if the nitrate concentration of the shallow groundwater at some location equals 68.6 g/m3, while according to the map it is 62.9 g/m3, then there will be no disagreement that in this case the error is 68.6 - 62.9 = 5.7 g/m3. Generalising this example, let the true value of a spatial attribute at some location x be a(x), and let the representation of it be b(x). Then, according to the definition, the error v(x) at x is simply the arithmetical difference v(x) = a(x) - b(x).
