Unbiasing is done by subtracting 'direct component' in each segment from the pixel values. This 'direct component' is either mean or median determined from all pixels in the segment. Both, mean and median were tried and results are very similar. The mean is easier to determine, thus it is preferred over the median. In such a case, the features give absolute description of the texture and can be used directly for classification.
Sea changes from scene to scene depending on factors like time of the day, weather, place, etc.
This concludes in fact that the co-occurrence can be skipped as unnecessary step and features can be applied directly onto the pixels of the image. The features differ across the scenes but for a particular scene they are stable and similar. If there is an object in the scene then the features exhibit considerable difference. One might argue that the features as presented here might be highly correlated and therefore redundant. We are aware of this fact and the thorough evaluation based on statistical principles is undergoing.