An agricultural harvesting machine, comprising: a controllable subsystem (102, 110, 113, 116, 118, 138); a forward-looking crop height sensor configured to detect an average height of the canopy of the crop over the sensed region in front of the harvesting machine in a direction of travel and generates a first sensor signal having a value indicative of the detected height of the crop canopy with respect to the sensor; volume generator logic configured to receive the first sensor signal and to generate a crop volume signal indicative of a volume of crop in the sensed region based on the detected height of the crop, the detected height of the crop determined based on the detected height of the crop canopy from which an elevation of the ground on which the crop is growing, with respect to the sensor, is subtracted; a component sensor (225, 229) configured to detect a characteristic of a component of the agricultural harvesting machine that is indicative of a biomass being processed by the agricultural harvesting machine, the component sensor (225, 229) adapted to generate a second sensor signal indicative of the detected characteristic; conversion factor generator logic configured to receive the first and second sensor signals and adapts a conversion factor intermittently during operation of the agricultural harvesting machine, the conversion factor being used to convert the characteristic of the crop to biomass, wherein the conversion factor is a volume to biomass conversion factor and wherein the conversion factor generator logic is configured to receive the crop volume signal and the second sensor signal indicative of the biomass being processed when the sensed region is reached by the harvesting machine and adapt the volume to biomass conversion factor based on the crop value signal and the second sensor signal indicative of the biomass; recommendation logic configured to receive the conversion factor and to generate a recommendation to change operation of the controllable subsystem (102, 110, 113, 116, 118, 138), based in part on the conversion factor and a value received from the forward-looking crop sensor; and a control system configured to control the controllable subsystem (102, 110, 113, 116, 118, 138) based on the generated recommendation; characterized in that the volume generator logic is configured to receive the elevation of the ground on which the crop is growing from a topographical map. a controllable subsystem (102, 110, 113, 116, 118, 138); a forward-looking crop height sensor configured to detect an average height of the canopy of the crop over the sensed region in front of the harvesting machine in a direction of travel and generates a first sensor signal having a value indicative of the detected height of the crop canopy with respect to the sensor; volume generator logic configured to receive the first sensor signal and to generate a crop volume signal indicative of a volume of crop in the sensed region based on the detected height of the crop, the detected height of the crop determined based on the detected height of the crop canopy from which an elevation of the ground on which the crop is growing, with respect to the sensor, is subtracted; a component sensor (225, 229) configured to detect a characteristic of a component of the agricultural harvesting machine that is indicative of a biomass being processed by the agricultural harvesting machine, the component sensor (225, 229) adapted to generate a second sensor signal indicative of the detected characteristic; conversion factor generator logic configured to receive the first and second sensor signals and adapts a conversion factor intermittently during operation of the agricultural harvesting machine, the conversion factor being used to convert the characteristic of the crop to biomass, wherein the conversion factor is a volume to biomass conversion factor and wherein the conversion factor generator logic is configured to receive the crop volume signal and the second sensor signal indicative of the biomass being processed when the sensed region is reached by the harvesting machine and adapt the volume to biomass conversion factor based on the crop value signal and the second sensor signal indicative of the biomass; recommendation logic configured to receive the conversion factor and to generate a recommendation to change operation of the controllable subsystem (102, 110, 113, 116, 118, 138), based in part on the conversion factor and a value received from the forward-looking crop sensor; and a control system configured to control the controllable subsystem (102, 110, 113, 116, 118, 138) based on the generated recommendation; characterized in that the volume generator logic is configured to receive the elevation of the ground on which the crop is growing from a topographical map.