A measuring anchor for measuring changes in the area surrounding a mining cavity constitutes an elongate rod-like member rigidly embedded by adhesive in a bore hole of such cavity. On the external surface of the rod-like member are diametrically opposed external recessed portions, such as grooves or flattened portions. Arranged respectively in axially spaced intervals on the outer side of the rod-like member and in pairs opposite each other in the recessed portions are sensors constituting strain gages for measuring changes in the strata surrounding same in several planes distributed over the length of the member. Strips cover the strain gages and are shaped to conform to that of the rod-like member. The sensors have leads which extend to the outside.