A 3D volume rate control method and apparatus (10) for a slewing bucket-wheel stockpile reclaimer 16 is described. The apparatus (10) comprises four 3D image sensors (12) mounted adjacent a bucket-wheel (14) of the (reclaimer 16), which are adapted to provide 3D images of a stockpile bench face. The apparatus includes a data processor (20) for: (i) processing the 3D images produced by the 3D image sensors (12) to generate a 3D stockpile bench face profile, (ii) calculating a reclaim cut volume rate at which material is being cut from the stockpile face based on a measured change in volume of the 3D stockpile bench face profile in the area abutting the excavation tool, (iii) calculating a reclaim cut volume of material that will be cut from the stockpile face based on the shape of the excavation tool and the 3D stockpile bench face profile to determine a feed forward reclaim cut volume rate profile, and (iv) calculating an operating parameter for the reclaimer based on a desired reclaim cut volume rate compared to the measured reclaim cut volume rate and the feed forward reclaim cut volume rate profile. The method and apparatus provide accurate reclaim volume measurement so that the reclaim volume rate becomes independent of the product characteristics, stockpile bench face shape and bucket-wheel cutting parameters.