1. A method for processing stereo vision data using image density, the method comprising: collecting, by an image collection system, image data comprising left image data and right image data of a particular scene; estimating an evaluated three dimensional image density rating for one or more respective evaluated volumetric cells within the particular scene; estimating a reference three dimensional image density rating for corresponding reference volumetric cell within the particular scene at a reference range from an imaging unit; compensating, using an image processor, for the change in image density rating between the reference volumetric cell and each evaluated volumetric cell by using a compensated image density rating based on a range or relative displacement between the reference volumetric cell and the evaluated volumetric cell, and by establishing a compensation curve as a function of compensated three dimensional image density versus range, for volumetric cells between the reference volumetric cell and the evaluated volumetric cell; and identifying a presence or absence of an obstacle in a particular compensated volumetric cell in the particular scene if the particular compensated volumetric cell meets or exceeds a minimum three dimensional image density rating.