1. A catheter system comprising: a plurality of mapping electrodes configured to detect activation signals of intrinsic cardiac activity, each of the plurality of mapping electrodes having an electrode location; a mapping processor associated with the plurality of mapping electrodes, the mapping processor configured to record the detected activation signals and associate one of the plurality of mapping electrodes with each recorded activation signal, the mapping processor further configured to generate a vector field map, comprising a plurality of vectors, which represents a direction of propagation of the activation signals at each electrode location, and identify a signature pattern and a target location in the vector field map according to at least one vector field template; and a display device configured to display the generated vector field map, wherein the mapping processor is further configured to determine a reliability index for each detected activation signal at an electrode location according to at least one of a contact between the corresponding electrode and an anatomical structure and a level of noise in the detected activation signal, and to modify the physical appearance of each of the plurality of vectors of the vector field map according to the corresponding reliability index to visually represent the reliability.