Derived variables can be collected directly from ground surveys. Mean of a variable is the value where half of the observations are smaller than this value and half are greater. Proportion is an outcome of the division of one variable by another. In the ratio scale the zero value indicates the lack of a variable. Some geographic information is divided into hierarchical classifications .
Geometric primitives are spatial objects that are too simple to be represented in the raster format.
Fuzzy modelling refers to an incorrect design of cause-effect GIS analysis. When conclusions are drawn about individuals in the area based on non-individual data an ecological fallacy is committed. Modifiable areal unit problem occurs when statistical characteristics of a variable are different at different levels of a variable s spatial aggregation. Aspect is the compass direction toward which a slope faces and it is measured in degrees from the east in a clockwise fashion. Database time refers to the exact definition of date and time of the database creation that is needed for appropriate data management.