Automatic past error corrections for location and inventory tracking
A system is provided for tracking and maintaining an inventory of location of containers that are stored on cargo ships or in a container yard. The system includes one or more sensors, such as GPS and INS sensors for obtaining real-time position information, as well as a processor configured to automatically provide post processing to recover lost data and to correct erroneous data, such as when real-time position signals are blocked or distorted, the post processing performed by estimating trajectories and correcting the location errors. Post-processed positioning techniques are continuously applied to the stored position data to iteratively determine calibrated position locations to provide calibrated second trajectory segments in a real-time fashion. The calibrated second trajectories are then used to identify the errors in the past real-time position data as soon as a segment of the second calibrated trajectory becomes statistically trustworthy. Corrections can be automatically made in inventory locations stored in a database to correct position errors for the containers.
1. A position tracking system comprising:
a positioning unit associated with a mobile object configured to provide first positions of the mobile object, wherein the positioning unit comprises sensors providing measurements related to positions of the mobile object and wherein the positioning unit provides the first positions in real time at discrete time instances with one of the first positions generated at each time instance;
a data storage unit configured to store the first positions in real time and configured to aggregate the stored first positions to form a first trajectory depicting past movement of the mobile object, wherein the first trajectory comprises a plurality of consecutive first positions;
a navigation processing module configured to generate second positions to form a second trajectory based on the first positions wherein the navigation processing module uses ones of the first positions corresponding to later time instances to determine the second positions corresponding to earlier time instances; and
an error correction computation module configured to compare the second trajectory from the navigation processing module with the first trajectory and generate correction data indicating data errors in the first trajectory,
whereby the second trajectory depicts the past movement of the mobile object more accurately than the first trajectory.
2. The system of claim 1 , further comprising a reporting module connected to the error correction computation module and configured to provide messages indicating locations and magnitudes of the said data errors in the first positions as stored in the data storage unit.
3. The system of claim 1 , wherein the positioning unit further comprises:
a first sensor configured to measure positions of the mobile object, and
a second sensor configured to provide at least one of the following information that supports determination of the first positions of the mobile object: linear motion data, angular motion data, linear velocity data, angular velocity data, linear acceleration data, and angular acceleration data;
whereby the positioning unit is configured to integrate measurements from the first sensor with measurements from the second sensor to provide the first positions.
4. The system in claim 1 , wherein the navigation processing module is further configured to generate the second trajectory by iteratively generating and calibrating an adjustable segment of the second trajectory data using a mathematical model for the mobile object until the adjustable segment is determined statistically trustworthy.
5. The system in claim 1 , wherein the error correction computation module is further configured to correlate the first trajectory with the second trajectory to identify segments of the first trajectory that require correction by comparing the data errors with a threshold, and wherein the data storage unit further stores the second trajectory corresponding to the identified segments of the first trajectory.
6. The system in claim 1 , wherein the error correction computation module updates the first position data with the corrected data to provide second position data and stores the second position data in the data storage unit.
7. The system in claim 1 , wherein the error correction computation module is further configured to report the correction data to an external device including at least one of a user interface and a database.
8. The system of claim 1 ,
wherein the positioning unit resides in the mobile object, and
wherein the navigation processing module and the error correction computation module reside away from the mobile object and are wirelessly linked to the positioning unit.
9. The system of claim 1 ,
wherein the positioning unit and the navigation processing module resides in the mobile object, and
wherein error correction computation module resides away from the mobile object and is wirelessly linked to the positioning unit and the navigation processing module.
10. The system of claim 1 ,
wherein the positioning unit, the navigation processing module and the error correction computation module reside in the mobile object.
11. The system of claim 1 ,
wherein the navigation processing module is further configured to employ a post-processing estimation filter to provide the second trajectory to more accurately depict the past movement of the object than the first trajectory.
12. The system of claim 4 , wherein when the adjustable segment is not determined statistically trustworthy after a predetermined number of times, the navigation processing module will extend a duration of the adjustable segment.
13. A position tracking system comprising:
a positioning unit associated with a mobile object configured to provide first positions of the mobile object, the positioning unit comprising:
a first sensor comprising a Global Positioning System (GPS) receiver configured to provide position measurements of the mobile object; and
a second sensor configured to provide at least one of a velocity of angular movement of the mobile object and a velocity for linear movement of the mobile object,
wherein the positioning unit includes a processor configured to provide first positions of the mobile object in real time based on a combination of outputs from the first and second sensors;
a data storage unit configured to store the first positions in real time and aggregating the stored first positions to form a first trajectory depicting past movement of the mobile object, wherein the first trajectory comprises a plurality of consecutive first positions;
a navigation processing module configured to generate second positions to form a second trajectory wherein the second positions are generated based on first positions of the first trajectory that have a higher trustworthiness level than other ones of the first positions of the first trajectory; and
an error correction computation module configured to compare the second trajectory with the first trajectory and to generate correction data indicating data errors in the first trajectory.
14. The system in claim 1 ,
wherein the positioning unit is further configured to provide trustworthiness levels associated with the first positions; and
wherein the navigation processing module is further configured to generate the second trajectory using the later positions which have higher ones of the trustworthiness levels than the earlier first positions.