TYPES OF ATTRIBUTE DATA:
Data types used in a GIS and in computer programming include character strings, integers, floating points or real numbers, dates and time intervals. Each field in an attribute table is defined with a data type, which applies to the domain of the field.Another method is to define attribute data by measurement scale. The measurement scale concept groups attribute data into nominal, ordinal, interval and ratio data.
(I) Nominal Data: - Nominal data describe different kinds of different categories of data such as land use types or soil types.
(II) Ordinal Data: - Ordinal data differentiate data by ranking relationship. For example-cities may be grouped into large, medium and small cities by population size.
(III) Interval Data: - Interval data have known intervals between values such as temperature reading. For example- a temperature reading of 700 F is warmer than 600 F by 100 F.
(IV) Ratio Data: - Ratio data are the same as interval data except that ratio data are based on a meaningful or absolute zero value. Population densities are an example of ratio data, because a density of 0 is an absolute zero.
