1. A method, comprising: recognizing touch input sensor data as a touch input on a touch-screen display; generating a sensor map from the touch input sensor data, the sensor map representing the touch input; modeling the sensor map as a Gaussian distribution; determining an ellipse that approximately encompasses the sensor map from the Gaussian distribution, the ellipse representing a contact shape of the touch input; and validating the ellipse based on an inaccuracy ratio (IAR) of the ellipse, the IAR of the ellipse determined from one or more regions that are within the bounds of the ellipse, but are not part of the sensor map.