The working methods commonly used in geodesy, as well as the procedures recently developed for use in geographic information systems (GIS), are based on geometrical and physical models which are more or less adequate approximations of reality.
The difference between the model and the reality is called uncertainty. In the traditional methods the uncertainty is modelled as a random variable and it is described and analysed by means of well-known statistical methods, for example using distributions, least squares estimation, univariate and multivariate analysis.
Alessandro Carosio
Fuzzy Techniques Robust Statistics