In this paper, some strategies to improve previous edge detection methods are given, and two different forms of improved theta map filters are presented. These filters use the power transform and the exponential transform of the theta map to recognise the edges of the sources. The new filters are demonstrated on synthetic and measured gravity and magnetic anomalies, and the resolving power of the new filters is tested by comparing the results with those obtained by the conventional theta map filter. The advantage of the new filters lies in their ability to delineate the source edges more clearly.