A system, comprising: a cylindrical calibration target that is placed in a monitored site, wherein the cylindrical calibration target has a physical appearance comprising: a first reflective section exhibiting first reflective properties; and a second reflective section displaying second reflective properties that are different from the first reflective properties, wherein, the first reflective section and the second reflective section are located on different portions of a curved surface of the cylindrical calibration target, wherein the physical appearance of the cylindrical calibration target includes non-uniform reflective properties; a first sensor (102 1) for capturing a first set of images of the cylindrical calibration target in the monitored site, wherein the first sensor has a first position in the monitored site, and wherein the first set of images depicts the first reflective section; a second sensor (102 n) for capturing a second set of images of the cylindrical calibration target in the monitored site, wherein the second sensor (102 n) has a second position in the monitored site that is different from the first position, and wherein the second set of images depicts the second reflective section; and a processor for determining a positional relationship of the first sensor (102 1) and the second sensor (102 n) by aligning the first set of images and the second set of images with a three-dimensional model of the cylindrical calibration target. a cylindrical calibration target that is placed in a monitored site, wherein the cylindrical calibration target has a physical appearance comprising: a first reflective section exhibiting first reflective properties; and a second reflective section displaying second reflective properties that are different from the first reflective properties, wherein, the first reflective section and the second reflective section are located on different portions of a curved surface of the cylindrical calibration target, wherein the physical appearance of the cylindrical calibration target includes non-uniform reflective properties; a first reflective section exhibiting first reflective properties; and a second reflective section displaying second reflective properties that are different from the first reflective properties, wherein, the first reflective section and the second reflective section are located on different portions of a curved surface of the cylindrical calibration target, wherein the physical appearance of the cylindrical calibration target includes non-uniform reflective properties; a first sensor (102 1) for capturing a first set of images of the cylindrical calibration target in the monitored site, wherein the first sensor has a first position in the monitored site, and wherein the first set of images depicts the first reflective section; a second sensor (102 n) for capturing a second set of images of the cylindrical calibration target in the monitored site, wherein the second sensor (102 n) has a second position in the monitored site that is different from the first position, and wherein the second set of images depicts the second reflective section; and a processor for determining a positional relationship of the first sensor (102 1) and the second sensor (102 n) by aligning the first set of images and the second set of images with a three-dimensional model of the cylindrical calibration target.