1. A method of detecting a location of a source of at least one cardiac rhythm disorder in a patient's heart using a system comprising at least one computing device, the computing device comprising at least one non-transitory computer readable medium configured to store instructions executable by at least one processor to determine the source and location of the cardiac rhythm disorder in the patient's heart, the system further comprising a monitor or screen operably connected to the computing device and a mapping electrode assembly, the method comprising: (a) acquiring electrogram signals inside the patient's heart using electrodes mounted on the mapping electrode assembly; (b) using the computing device, normalizing or adjusting the amplitudes of the electrogram signals acquired from the electrodes located inside the patient's heart; (c) using the computing device, assigning positions or identifiers for each of the electrodes to corresponding individual electrogram signals; (d) using the computing device, providing or generating a two-dimensional (2D) spatial map of the electrode positions; (e) using the computing device, and for each or selected discrete times over which the electrogram signals are being processed, processing the amplitude-adjusted electrogram signals to generate a plurality of three-dimensional electrogram surfaces corresponding at least partially to the 2D map, one surface being generated for each such time, and (f) using the computing device, processing the plurality of three-dimensional electrogram surfaces through time to generate and display on the monitor or screen a velocity vector map corresponding at least partially to the 2D map, the velocity vector map being configured to reveal the location of the source of the at least one cardiac rhythm disorder so that a user can diagnose or treat the patient.