Although mathematical models of surfaces are widely used in the process of estimating the values of attributes at all locations, typically the data is represented in grid form for the purposes of subsequent analysis. Whilst this does not have the elegance of a mathematical model, and is far less compact as a form of representation, it is extremely well-suited to computer-based analysis. As a result, almost all GIS-based surface analysis, including purely geometric processing, tends to be based on the grid representation of a surface rather than equations, level sets (contours) or triangulations (TINs).