Patent ID: 8319634

Claim:
A method of determining whether an article is present in a predetermined three-dimensional volume at a particular time, comprising: defining a three-dimensional trajectory envelope, wherein the three-dimensional trajectory envelope is defined by X, Y, and Z coordinates, and wherein the X, Y, and Z coordinates defining the three-dimensional trajectory envelope comprise a width, length, and height, respectively, of the three-dimensional trajectory envelope; determining a position of a first transducer associated with the article, at each of a plurality of successive instants preceding the particular time, the position of the first transducer comprising X, Y, and Z coordinates of the first transducer associated with the article; determining a position of a second transducer associated with a coupler of a crane as the crane displaces the article between first and second locations, at each of a plurality of successive instants preceding the particular time, the coupler attaching the article to the crane, the position of the second transducer comprising X, Y, and Z coordinates of the second transducer; determining, using a computer device, whether the X, Y, and Z coordinates of each successive position of the first transducer associated with the article, and of each successive position of the second transducer associated with the coupler of the crane, lie within the X, Y, and Z coordinates defining the three-dimensional trajectory envelope as the article is displaced by the crane between the first and second positions; and in a case where all of the positions of the first and second transducers are determined to lie within the X, Y, and Z coordinates defining the three-dimensional trajectory envelope, registering the article as present in the predetermined three-dimensional volume.