1. A method for localizing an activation site of origin to a segment of the heart comprising: obtaining a body-surface potential map (BSPM) of interest based on a plurality of simultaneously recorded electrocardiographic (ECG) signals from a first plurality of at least three leads; calculating an integral of the signal recorded from a second plurality of leads selected from the first plurality of leads wherein the second plurality of leads comprises between two leads and one less than the first plurality of leads and identifying a condition of the integral as positive or negative for each of the second plurality of leads; comparing the identified condition of each of the second plurality of leads with a condition of a plurality of pre-determined sets of BSPM templates, each set comprising one BSPM template for each pre-defined segment of the heart, to identify a selected set of BSPM templates having matching conditions; comparing the body surface potential map of interest to each BSPM template of the selected set of BSPM templates, wherein comparing comprises, for each BSPM template of the set of BSPM templates: retrieving a BSPM template from memory from the selected set of BSPM templates; and calculating one or more comparison metrics for the BSPM template retrieved as compared to the BSPM of interest, wherein each of the BSPM templates was generated by averaging BSPMs of all pacing sites within the associated segment of the heart from a collection of BSPMs stored in memory; and identifying the BSPM template that most closely resembles the BSPM of interest using the one or more comparison metrics calculated in order to identify the segment of the heart in which the activation site of origin is likely to be located.