A method of atrial focal source detection is provided which includes detecting, via sensors, electro-cardiogram (ECG) signals over time. Each ECG signal is detected via one of the sensors and indicates electrical activity of a heart. The method also includes determining, for each ECG signal, local activation times (LATs) each indicating a time of one of a plurality of atrial activations of a corresponding ECG signal and detecting whether one or more focal source areas of activation in the heart is indicated based on the detected ECG signals and the one or more local LATs. S-waves can be distinguished from non-S-waves by generating models for each atrial activation and classifying atrial activations. Maps can be generated by visually indicating, for each sensor, a level of incidence of the atrial activations occurring before atrial activations of neighboring sensors within a period of time.
