Using this filter, reflections and glare can be reduced significantly from non-metallic surfaces. Also it will help to greatly reduce the softness caused by atmospheric haze.
PL filters achieve their greatest effect of eliminating glare when used at a 30-40 degree angle to a reflective surface (like glass or water). At midday when the sun is directly overhead, or at a 90 degree angle, the filter will have the least effect. These effects are easily visible by rotating the filter and looking through the viewfinder of the camera. Keep in mind that you will first need to adjust the polarizing filter before setting the exposure controls.