1. A surface anomaly detection system for detecting anomalies on a surface, the detection system comprising: a synthetic aperture focusing device, the synthetic aperture focusing device configured to apply guided waves to the surface and generate image data of the surface, the image data comprising a plurality of pixels; a noise filter, the noise filter configured to receive the image data of the surface, the noise filter configured to generate a mean value for each of the plurality of pixels, wherein the noise filter comprises a modified Kalman filter configured to implement a stochastic model to estimate the mean value of each of the plurality of pixels; a threshold detector, the threshold detector configured to receive the mean value for each the plurality of pixels, the threshold detector configured to evaluate the mean value for each of the plurality of pixels using a threshold to determine which of said plurality of pixels exceed the threshold; a contour detector, the contour detector configured to determine a contour of pixels that exceed the threshold using a principal curves technique; and a severity estimator, the severity estimator configured to calculate an anomaly factor based on a parameter of the contour.