An automatic method of determining local activation time (LAT) in multi-channel cardiac electrogram signals including a plurality of cardiac channels, the method comprising: (a) storing the cardiac channel signals； (b) selecting a mapping channel, a ventricular channel, and a reference channel from among the plurality of cardiac channels； (c) using the selected channels to compute first LAT values at a plurality of mapping-channel locations； (d) monitoring the quality of at least one selected channel； (e) if the quality of a monitored cardiac channel falls below a standard, replacing the sub-standard channel with another channel of the plurality of channels having an above-standard quality； and (f) computing second LAT values based on the replacement cardiac channel.
