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) using a ventricular, a reference and a mapping channel to compute first LAT values at a plurality of mapping-channel locations; (c) monitoring the quality of at least one of the ventricular, reference and mapping channels; (d) 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 (e) computing second LAT values based on the replacement cardiac channel.