A combine comprising: a feeder housing for receiving harvested crop; a separating system for threshing the harvested crop to separate grain from residue; a grain tank (28, 212, 501) for storing the separated grain; a controler that controls the combine; characterized in that the combine further comprises: a grain tank level sensor side array (100, 102, 204, 206, 208, 210, 214, 503A, 503C) at the side of the grain tank (28, 212, 501) for detecting a level of grain in the grain tank (28, 212, 501) at the side of the grain tank (28, 212, 501); a grain tank level sensor center array (101, 103, 209, 211, 215, 503B) in the center of the grain tank (28, 212, 501) for detecting a level of grain in the grain tank (28, 212, 501) in the center of the grain tank (28, 212, 501) and that the controller is configured to: - receive the level of grain from the grain tank level sensor side array (100, 102, 204, 206, 208, 210, 214, 503A, 503C), - determine a volume of a grain base from the level of the grain, - receive the level of grain from the grain tank level sensor center array (101, 103, 209, 211, 215, 503B) - determine a volume of a grain heap above the grain base, and - determine a total volume by combining the volume of the grain base with the volume of the grain heap. a feeder housing for receiving harvested crop; a separating system for threshing the harvested crop to separate grain from residue; a grain tank (28, 212, 501) for storing the separated grain; a controler that controls the combine; characterized in that the combine further comprises: a grain tank level sensor side array (100, 102, 204, 206, 208, 210, 214, 503A, 503C) at the side of the grain tank (28, 212, 501) for detecting a level of grain in the grain tank (28, 212, 501) at the side of the grain tank (28, 212, 501); a grain tank level sensor center array (101, 103, 209, 211, 215, 503B) in the center of the grain tank (28, 212, 501) for detecting a level of grain in the grain tank (28, 212, 501) in the center of the grain tank (28, 212, 501) and that the controller is configured to: - receive the level of grain from the grain tank level sensor side array (100, 102, 204, 206, 208, 210, 214, 503A, 503C), - determine a volume of a grain base from the level of the grain, - receive the level of grain from the grain tank level sensor center array (101, 103, 209, 211, 215, 503B) - determine a volume of a grain heap above the grain base, and - determine a total volume by combining the volume of the grain base with the volume of the grain heap. a grain tank level sensor side array (100, 102, 204, 206, 208, 210, 214, 503A, 503C) at the side of the grain tank (28, 212, 501) for detecting a level of grain in the grain tank (28, 212, 501) at the side of the grain tank (28, 212, 501); a grain tank level sensor center array (101, 103, 209, 211, 215, 503B) in the center of the grain tank (28, 212, 501) for detecting a level of grain in the grain tank (28, 212, 501) in the center of the grain tank (28, 212, 501) and that the controller is configured to: - receive the level of grain from the grain tank level sensor side array (100, 102, 204, 206, 208, 210, 214, 503A, 503C), - determine a volume of a grain base from the level of the grain, - receive the level of grain from the grain tank level sensor center array (101, 103, 209, 211, 215, 503B) - determine a volume of a grain heap above the grain base, and - determine a total volume by combining the volume of the grain base with the volume of the grain heap. - receive the level of grain from the grain tank level sensor side array (100, 102, 204, 206, 208, 210, 214, 503A, 503C), - determine a volume of a grain base from the level of the grain, - receive the level of grain from the grain tank level sensor center array (101, 103, 209, 211, 215, 503B) - determine a volume of a grain heap above the grain base, and - determine a total volume by combining the volume of the grain base with the volume of the grain heap.