A luffing-jib tower crane, comprising a tower and a jib which is connected to the tower via a joint and is held by a luffing cable, wherein the length of the luffing cable can be changed by a drawing-in unit, by the luffing cable being wound onto or unwound from a cable drum of the drawing-in unit, wherein the angle of the jib with respect to the horizontal plane is measured by a first sensor winch is attached to the jib (first angular value), wherein a measuring device measures the length of the unwound part of the luffing cable, from which length the minimum angle of the jib with respect to the horizontal plane (second angular value) can be calculated, and the first angular value can be compared with the second angular value.