Both horizontal and vertical calculation grids are needed for obtrusive light calculations and must be able to be positioned according to the site feature they represent. A calculation grid may be required which represents the wall of a dwelling which is at some odd angle to the co-ordinate system being used in the design. Application programs do not necessarily have this ability. Calculation grids need to handle more than one light parameter. E.g. a grid representing a window may need vertical illuminance and intensity from each luminaire to be calculated.
Some application programs handle only one parameter per run.
Thus using conventional programs for both the application and obtrusive parameters becomes tedious as factors need to be included then excluded depending on the current parameter being calculated. The effect of obstructions needs to be considered. Application design less frequently requires obstructions to be considered, hence not all programs have this capability. Application design is usually evaluated over an area with average, minimum, and maximum values being used to assess compliance with design objectives. Isolines, shaded diagrams etc are often used to evaluate the pattern to permit design adjustments.