An automatic method of determining local activation time (LAT) in multi-channel cardiac electrogram signals including at least two cardiac channels, one of the cardiac channels being a mapping channel and another cardiac channel being a reference channel, the method comprising: (a) estimating a cycle length CL in the reference channel (b) determining a mapping-channel fiducial time tM in the mapping channel signal (c) determining a plurality of reference-channel fiducial times tR (d) computing adjusted reference-channel fiducial times tRA by adding or subtracting multiples of cycle length CL to each time tR such that each time tRA is within a time window of length CL surrounding mapping-channel fiducial time tM (e) computing a single final reference-channel fiducial time tRF from the plurality of adjusted reference-channel fiducial times tRA and (f) computing the LAT as tM minus tRF.
