POSITION ESTIMATING SYSTEM, POSITION ESTIMATING UNIT, WORK MACHINE, AND EXTENSION UNIT

A position estimating system includes a first posture detector disposed in a linkage mechanism, and a controller that estimates information regarding the position of a bucket with respect to a work machine based on data regarding a shape of a first work implement, data regarding a shape of a second work implement, information regarding a posture of the first work implement, and a value detected by the first posture detector. The second work implement includes an extension part having a first end portion connectable to the bucket and a second end portion connectable to an arm. The linkage mechanism includes a first linkage part connected to the extension part through a first coupling portion, a second linkage part connected to the first linkage part through a second coupling portion, and a third linkage part disposed closer to the second end portion than the first linkage part.