When treating atrial arrhythmias using catheter ablation it is standard practice to create local activation maps of a patient’s atrium to guide treatment. Generating these maps involves recording hundreds of electrograms from the inside surface of the chamber and then using automated algorithms to identify deflections in the signal and choose the activation time for each recording point. The activation times are then visually represented on a 3D model of the chamber which is used to guide treatment. However, uncertainty in the selection of the activation time is not considered by the algorithm and may lead to poor quality data collection. To the best of our knowledge, this is the first attempt to quantify and communicate the uncertainty of each activation time.