Examples of possible source classes. The black outline shows the island threshold, the magenta ellipses show the individual Gaussian components fit to to the source, and the blue ellipses show the combined Gaussian describing the source. From left to right: (i) an elongated source fit by two Gaussian components. The combined Gaussian describes the source adequately, and it has been assigned the 'G' class. (ii) A likely FRI source with complex structure, better described by the island than the Gaussian components. It has been assigned the 'I' class. (iii) A point source with an additional noise peak that has been fitted with a Gaussian component. It has been assigned the 'P' class. (iv) An artefact caused by a nearby bright source. It has been assigned the 'A' class.