The amount in which a property changes in elevation. National Ramp installers measure the ground elevation at the start and ending points of the ramp to determine if there is a grade variation, and if more or less ramping will be required than the elevation alone would dictate. The starting elevation of the ramp (from the doorway, stairs, porch) plus or minus the change in grade variation determines the total rise with slope, or the amount needed to achieve a 4.8* angle.