A key ingredient of systems aiming to cope with multiple representations of geographic features is some method for assessing the
correspondence and similarity of such representations. In other words, given two objects from two different data sources, one must be able to tell whether they model the same real world object and, in this case, measure their degree of similarity. 

This plugin is an implementation of the Equivalents Rectangles Method (ERM) to quantify the average distance between ambiguous cartographic representations and uses the Cartographic Similarity Index (CSI) or Geographic Similarity Index (CSI)  – an index based on areal distances – to evaluate how much a given geometric representation resembles another. At the moment this plugin works by comparing two layers. Each layer must have only one polygon.