A method and apparatus for profiling the bed of a furnace involves the production of a digital image of the bed and background. The digital image is processed to determine transitions in the image which correspond to transitions between the bed and background and thereby to the boundary of the bed. Bed characteristics, such as the bed profile, the bed height, the slope of the bed and the volume of the bed are determined from the processed image. The image may be displayed for use in controlling the performance of a furnace. In addition, the determined bed characteristics may be compared with reference bed characteristics, with the differences being displayed, used in controlling the operation of the furnace, or in activating an indicator, such as an alarm, in the event the reference and determined bed characteristics differ by a threshold amount.