A doubt about two methods about distance calculation

[yipwan]

Hi, I have a question about the distance calculation on bbox and Re-ID feature。When calculating distance between two bbox（prediction and detection）, the author use Mahalanobis distance. When calculating distance between two Re-ID feature, the author use cosine distance. I doubt that why the author use two different method to calculate distance. Is it due to the convenience that the Kalman Filter has already calculated the Covariance matrix which is used in calculating Mahalanobis distance ?