This disclosure provides one or more computer-readable media having computer-executable instructions for performing a method. The method includes storing geometry data representing a primary geometry of a cardiac envelope that includes nodes distributed across the cardiac envelope and geometry of a body surface that includes locations where electrical signals are measured. The body surface is spaced apart from the cardiac envelope. The method also includes perturbing the primary geometry of the cardiac envelope a given distance and direction to define the perturbed geometry of the cardiac envelope including nodes spaced from the nodes of the primary geometry. The method also includes computing reconstructed bipolar electrical signals on the nodes of the primary cardiac envelope based on the electrical signals measured from the body surface and the geometry data, including the primary and perturbed geometries of the cardiac envelope.