Abstract:
A container tracking system comprises a dispatcher workstation with a graphical user interface and a database. These are used to track the whereabouts of shipping containers in a storage and transfer yard. A mobile unit in the yard is attached to container handling equipment and monitors the container lock-on mechanism. When a container is locked on for a move, the mobile unit starts reporting positions and velocities to the dispatcher workstation over a radio channel. These positions and solutions are computed from a combination of GPS satellite navigation receiver solutions, inertial navigation, and local beacon markers. Reports stop when the container handling equipment unlocks from the container. The database then updates the new position for that container, and the graphical user interface can be used to “see” the container on a yard map.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to material-handling systems, and more particularly to computerized systems for tracking the real-time locations of shipping containers. 
     2. Description of Related Art 
     On the West Coast of the United States, shipping container handling volumes have been increasing dramatically. In 1999, container twenty-foot equivalent units (TEU&#39;s) increased almost 10% to 8M TEU&#39;s. This was half of the total TEU&#39;s for the entire country. Ten years ago, the West Coast was handling less than 4M TEU&#39;s. 
     Such increases in handling volume are adversely affecting real-time order visibility. But every partner to the transactions needs to have access to location information throughout a container&#39;s journey. In port, containers are routinely not visible to the consignees, and this produces some consternation. 
     Yard operations are the most time consuming in overall average transactions. Out-gate operations take less time, guard operations require less than that, and in-gate operations are the least time consuming. During yard operations, a yard clerk must accompany the truck driver to validate the correct container for pick-up. But if the container is not where it is supposed to be, the typical yard clerk wanders around the yard looking for it. Then the equipment operator and truck driver have to be radioed to come to the new location. Even so, the right container might be buried by others that need to be moved out of the way, all while the yard clerk and truck driver are waiting. It would be better if the equipment operator could have the container free to load and in a verified location by the time the truck arrives. 
     Prior art systems and methods have experimented with attaching marks, markers, bugs, radios, GPS equipment, and other devices to the shipping containers. These devices then ride along through the entire trip. But putting such things on each container is expensive, and the devices are often blocked for some reason and not accessible. Device incompatibilities also are common because no world standard exists. It&#39;s hard enough to stick with a single standard within one storage and transfer yard. 
     The use of simple identification labels on material and the tracking of them is described by Harold Terrence Salive, et al., in U.S. Pat. No. 5,725,253, issued Mar. 10, 1998. The labels are visual graphics that are captured by a digital imaging camera. 
     Joseph Radican describes a container monitoring system and method in U.S. Pat. No. 5,712,789, issued Jan. 27, 1998. The system can generate status reports for customers, suppliers, and shippers about their respective containers. A container management information system is updated with container identification and location data. 
     A GPS navigation receiver is coupled with a cellphone, and both are attached to a shipping container in U.S. Pat. No. 5,835,377, issued Nov. 10, 1998, to Ronald Bush. Such tracking module is described as being built into each shipping container. 
     Each such patent mentioned herein is incorporated by reference. 
     SUMMARY OF THE INVENTION 
     Briefly, a container tracking system embodiment of the present invention comprises a dispatcher workstation with a graphical user interface and a database. These are used to track the whereabouts of shipping containers in a storage and transfer yard. A mobile unit in the yard is attached to container handling equipment and monitors the container lock-on mechanism. When a container is locked on for a move, the mobile unit starts reporting positions and velocities to the dispatcher workstation over a radio channel. These positions and solutions are computed from a combination of GPS satellite navigation receiver solutions, inertial navigation, and local beacon markers. Reports stop when the container handling equipment unlocks from the container. The database then updates the new position for that container, and the graphical user interface can be used to “see” the container on a yard map. 
     An advantage of the present invention is that a system is provided that keeps track of the locations of shipping containers in a storage and transfer yard. 
     Another advantage of the present invention is that a system is provided that reduces or eliminates the number of “lost” or misplaced shipping containers in a yard. 
     A further advantage of the present invention is that a system is provided that locates shipping containers to precise locations in a yard. 
     The above and still further objects, features, and advantages of the present invention will become apparent upon consideration of the following detailed description of specific embodiments thereof, especially when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a functional block diagram of a container tracking system embodiment of the present invention; and 
     FIG. 2 is a perspective diagram of a transtainer in a container storage and transfer yard that uses the system of FIG.  1 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 illustrates a container tracking system embodiment of the present invention, referred to herein by the reference numeral  100 . The system  100  includes a mobile unit  102  that fastens to a bridle piece of container handling equipment, e.g., a rubber-tired transtainer or container crane, a side loader, a top loader, or a yard tractor. Such is in radio communication with a dispatcher&#39;s base station  104 . A radio link between them communicates real-time position change information whenever a container is locked onto, moved, and released. The particular containers are identified by their starting positions in three-dimensional space. An index of container identities to their three-dimensional positions is kept in a database  106 . A computer workstation  108  is connected to both the database  106  and a display screen  110 . A graphical user interface (GUI)  112  is provided on-screen and can represent the three-dimensional positions of the containers in a yard being tracked with a map. Such map is preferably clickable, i.e., includes hypertext links that can be selected for navigating between elements and screen pages. Initial and corrective information about various containers can be entered by an authorized user at the workstation  108 . A wireless transceiver  114  provides the actual communications link to a similar transceiver  116  in the mobile unit. A dispatcher at the base station  104  can instruct an operator at the mobile unit  102  as to which containers are to be moved where, e.g., by voice or by e-mail messaging. A computer program may later test to see that those instructions were followed correctly. 
     The mobile unit determines its position, e.g., from a mixture of at least one of global positioning system (GPS) satellite navigation receiver solutions, inertial navigation solutions (INS) and pseudo-noise (PN) beacon readings. A combination of all three is preferred for accuracy and availability. The INS provides continuous position solutions, but these are subject to long-term drift that is readily corrected by the GPS and PN. A navigation computer (NAV)  118  receives position data from a GPS receiver  120 , a pseudo-noise receiver  122 , and an inertial navigation computer  124 . The GPS solutions can be improved by constraining the solutions with the storage yard&#39;s elevation, discrete container stacking heights, and the container yard&#39;s perimeters. These can be provided by a complete survey and mapping of the yard that is represented as an electronic terrain model and map in the database  106 . 
     Suitable GPS receiver equipment is available from Trimble Navigation (Sunnyvale, Calif.). The INS can be implemented with an inertial measurement unit (ISIS-IMU) made by Inertial Science, Inc. (Newbury Park, Calif.). 
     A three-dimension accelerometer  126 , for example, is used to provide direction of movement and movement acceleration magnitude information. A lock detector  128  senses when a container transporter has locked onto a container and is mechanically able to lift and relocate the container. Such locking triggers the NAV  118  to start generating movement and trajectory information, and the generated data is preferably sent in real-time back to the dispatcher base station  104 . New information about container movements are used by the workstation  108  to update the database  106 . The GUI  112  represents the current information in an easy to understand graphic map representation. 
     A network of PN beacons  130 - 133  are disposed at known positions throughout the container storage yard. When a mobile unit  102  passes over one, the survey information can be plugged in as correction data. In one embodiment, a form of differential correction information can be derived from the PN beacons to improve the solution accuracy of the GPS  120 . Trigger-wires, light beams, lasers and other devices at strategic locations throughout the yard can be used by the PN beacons  130 - 133  to determine the exact boundary being crossed by the mobile unit  102 . These can be homogeneous, except for their locations, and the GPS and INS solutions can be used to identify the particular PN beacon being encountered. The PN beacon mark can nail down a location fix to better than a centimeter, and this can be used to fine-tune and correct the GPS and INS solutions that are obtained between PN beacon locations. 
     A pseudo-lite  134  is alternatively positioned in the container storage yard at a known, well-surveyed position. It mimics an orbiting GPS satellite, and transmits an appropriate almanac and ephemeris associated with its fixed position. The GPS  120  accepts this as yet another datum in a constellation, and the pseudo-lite  134  may contribute greatly due to the advantageous solution geometries that can be obtained. 
     The practical implementations of the PN beacons  130 - 133  and PN receiver  122  may depend on different fundamental technologies, e.g., radio waves, laser beam interruption, recognition of patterns placed on the ground surface, etc. The object is to send a signal from a known location to the mobile unit  102  when it passes nearby, so that such signal can be interpreted as a physical-position calibration mark. 
     FIG. 2 shows a container handling system embodiment of the present invention, and is referred to herein by the general reference numeral  200 . A transtainer  202  is able to move left and right along direction  204 , e.g., along a railway or roadbed. The transtainer  202  has a gantry  206  that can reach out in a direction  208  with a bridle  210  to move any of a group of containers  212 . 
     As an example of a typical logistic problem facing a storage and transfer yard, a number of containers “A” need to be shipped out today, a group “B” tomorrow, and a group “C” the day after. The bridle  210  is equipped with the mobile unit  102  (FIG. 1) and this makes it possible for a dispatcher to orchestrate the necessary moves that will make container groups “A”, “B”, and “C” available with the least amount of delay, confusion, effort, and labor. In alternative embodiments of the present invention, the workstation  108  includes a computer program for scheduling, logistical strategies, and position changes for the containers  212 . 
     A row of magnets  214  are laid down in the roadbed at regular intervals and all in parallel. The directional placement of their magnetic poles spells out a code that can be magnetically read by PN receiver  122 . Alternatively, a series of visual symbols can be substituted for the row of magnets  214 , and the PN receiver reads them by a video imaging camera. The row of magnets  214  is laid out in a pattern that mimics a pseudo-random number (PRN). Such resembles the PRN modulation impressed on microwave carriers by GPS satellites and that are read by GPS receivers. The code phase of the PRN word corresponds to the physical position of the reader. 
     The PN receiver  122  reads a magnetic signal it receives from the row of magnets  214  as the transtainer  202  moves in direction  204 . A code phase is determined and this is used by NAV  118  to compute the position of bridle  210  and any container it has locked to. Such magnetic codes can be laid out in any convenient direction, not just left and right as illustrated in FIG.  2 . 
     A method embodiment of the present invention for managing inventories in a storage area comprises electronically mapping a three-dimensional storage area in which pieces of inventory come-in, go-out, and shuffle between internal locations. Then cataloging and indexing each piece of an inventory according to its identity and location within the storage area. A navigation computer is attached to a piece of machinery that is able to move the pieces of inventory around in the storage area. The method detects when the piece of machinery is attached to move any of the pieces of inventory. And it reports any position solutions derived from the navigation computer that can be attributed to movements of a particular piece of inventory. A database is updated with a new imputed position of each piece of inventory that has been moved to a new location by the piece of machinery. 
     Alternative embodiments further display a map representation of the storage area and each of the pieces of inventory on a computer screen through a graphical user interface (GUI). 
     The steps of attaching and detecting include attaching the navigation computer to a bridle on a transtainer, and detecting when the bridle locks onto a shipping container one of the pieces of inventory. The step of attaching can also include attaching a navigation computer which includes at least one of a navigation satellite receiver, inertial navigation sensor, and a pseudo-noise receiver. 
     Other embodiments of the present invention magnetically encode a digital pseudo-random number in a pattern along linear runs within the storage yard. The pattern is read as the piece of machinery passes by it. A code phase of the pattern is interpreted as correlating to a particular linear position within the storage area. And it used in the step of updating to associate a shipping container with its new position. 
     Although particular embodiments of the present invention have been described and illustrated, such is not intended to limit the invention. Modifications and changes will no doubt become apparent to those skilled in the art, and it is intended that the invention only be limited by the scope of the appended claims.