An anatomical mapping system comprising: a plurality of mapping electrodes disposed in or near the anatomical structure configured to detect activation signals during an instance of physiological activity; a processing system associated with the plurality of mapping electrodes, the processing system configured to record the detected activation signals and associate one of the plurality of mapping electrodes with each recorded activation signal, the processing system further configured to generate a vector field for each sensed activation signal during each instance of the physiological activity; determine an onset time and alternative onset time candidates for each activation signal; identify an initial vector field pattern template for each activation signal based on a degree of similarity between the generated vector field and at least one vector field template pattern; iteratively update or replace the initial onset time with corresponding onset time candidates, wherein a vector field candidate is generated for each onset time candidate, each vector field candidate is compared to the initial pattern template and a similarity index is determined, and, if the current similarity index is greater than the initial similarity index, the initial onset time is updated or replaced with the onset time candidate, the initial vector field is updated with the new initial onset time, and the similarity index is updated or replaced by the current similarity vector, until an optimized onset time is determined for each initial onset time. a plurality of mapping electrodes disposed in or near the anatomical structure configured to detect activation signals during an instance of physiological activity; a processing system associated with the plurality of mapping electrodes, the processing system configured to record the detected activation signals and associate one of the plurality of mapping electrodes with each recorded activation signal, the processing system further configured to generate a vector field for each sensed activation signal during each instance of the physiological activity; determine an onset time and alternative onset time candidates for each activation signal; identify an initial vector field pattern template for each activation signal based on a degree of similarity between the generated vector field and at least one vector field template pattern; iteratively update or replace the initial onset time with corresponding onset time candidates, wherein a vector field candidate is generated for each onset time candidate, each vector field candidate is compared to the initial pattern template and a similarity index is determined, and, if the current similarity index is greater than the initial similarity index, the initial onset time is updated or replaced with the onset time candidate, the initial vector field is updated with the new initial onset time, and the similarity index is updated or replaced by the current similarity vector, until an optimized onset time is determined for each initial onset time. generate a vector field for each sensed activation signal during each instance of the physiological activity; determine an onset time and alternative onset time candidates for each activation signal; identify an initial vector field pattern template for each activation signal based on a degree of similarity between the generated vector field and at least one vector field template pattern; iteratively update or replace the initial onset time with corresponding onset time candidates, wherein a vector field candidate is generated for each onset time candidate, each vector field candidate is compared to the initial pattern template and a similarity index is determined, and, if the current similarity index is greater than the initial similarity index, the initial onset time is updated or replaced with the onset time candidate, the initial vector field is updated with the new initial onset time, and the similarity index is updated or replaced by the current similarity vector, until an optimized onset time is determined for each initial onset time. a vector field candidate is generated for each onset time candidate, each vector field candidate is compared to the initial pattern template and a similarity index is determined, and, if the current similarity index is greater than the initial similarity index, the initial onset time is updated or replaced with the onset time candidate, the initial vector field is updated with the new initial onset time, and the similarity index is updated or replaced by the current similarity vector, until an optimized onset time is determined for each initial onset time.