Control is imposed on one or more dimensions so another dimension can be measured.
The imposition of control results in a loss of information that contributes to the uncertainty about the variable or phenomena being described. Work on uncertainty has tended to focus on measurement errors, yet the effects of control may be more substantial particularly for spatial and spatio-temporal representations. In other words the imperfections in the measurements are less cause for concern than that which is not measured. Attempts to monitor and measure the reliability of geographic representations need to track the effects of control and the interaction of multiple control effects. This paper develops an approach using the example of spatial control which can be generalized to temporal and some forms of thematic control.