Proportional Symbol Proportional or graduated symbol is one of the most popular mapping techniques. It is a good way of representing both absolute and rate types of variables. Technique this however is not recommended when showing a density of distribution is important . A number of different shapes can be applied, circles, squares, triangles, bars and others. In most cases the area of the proportional symbol represents the magnitude of the phenomena.
Symbols can represent an aggregated value of a region or a value of a point feature.
Proportional maps can be used to represent many different kinds of variables such as socioeconomic, physical, demographic etc. Proportional symbol maps give plenty of flexibility to the mapping process. Area of the circle is usually scaled to the square root of the data. This is called absolute scaling. This problem can be addressed by using apparent-magnitude scaling, technique that makes the area of a circle grow relatively faster than the magnitude of the phenomena.