Third, gait energy image and PCA is computationally more
efficient than PCA and it can improve the speed of image feature
extraction significantly. Image representation and recognition
based on gait energy image and PCA is statistically dependent on
the evaluation of the covariance matrix (although for PCA the
explicit construction of the covariance matrix can be avoided).
The obvious advantage of gait energy image and PCA over PCA
is that the former evaluates the covariance matrix more
accurately. Also time needed to extract the feature is less in gait
energy image and PCA with respect to PCA.