Correlating Overlapping Magnetic Measurement Data from Multiple Magnetic Navigation Devices and Updating a Geomagnetic Map with that Data

Abstract

In one embodiment, a method includes accessing a geomagnetic map that incorporates one or more portions of one or more trajectories from one or more magnetic-measurement devices comprising magnetic measurements in an area collected by the magnetic-measurement devices over a period of time. The portions of the trajectories were incorporated into the magnetic map based on similarities in the trajectories determined at least in part by one or more correlation analyses performed on at least portions of the trajectories. The method also includes performing localization or navigation using the geomagnetic map.

What is claimed is: 
     
         1 . A method comprising:
 by a computing device, accessing a geomagnetic map that incorporates one or more portions of one or more trajectories from one or more magnetic-measurement devices comprising magnetic measurements in an area collected by the magnetic-measurement devices over a period of time, wherein the portions of the trajectories were incorporated into the magnetic map based on similarities in the trajectories determined at least in part by one or more correlation analyses performed on at least portions of the trajectories; and   by the computing device, performing localization or navigation using the geomagnetic map.   
     
     
         2 . The method of  claim 1 , wherein performing the correlation analyses and incorporating into the geomagnetic map portions of the trajectories comprises:
 for each of one or more portions of one or more of the trajectories: 
 comparing the portion of the trajectory with a corresponding portion of a baseline magnetic map according to a correlation analysis to determine similarity between the portion of the trajectory and the corresponding portion of the baseline magnetic map; and 
 storing the portion of the trajectory based on the determined similarity between the portion of the trajectory and the corresponding portion of the baseline magnetic map; 
   for each of one or more of the stored portions of the trajectories: 
 comparing the portion of the trajectory with one or more corresponding other ones of the stored portions of the trajectories according to a correlation analysis to determine similarity between it and the corresponding other ones of the stored portions of the trajectories; and 
 continuing to store the portion of the trajectory based on the determined similarity between the portion of the trajectory and the corresponding other ones of the stored portions of the trajectories; and 
   for each of one or more of the portions of the trajectories that is still stored, further continuing to store the portion of the trajectory based on a weighting of the portion of the trajectory.   
     
     
         3 . The method of  claim 2 , wherein:
 the geomagnetic map comprises the baseline geomagnetic map; and   the baseline geomagnetic map comprises an Earth Magnetic Anomaly Grid with 2-arc-minute resolution (EMAG2) model.   
     
     
         4 . The method of  claim 2 , wherein the weighting of the portion of the trajectory is based at least in part on a trust coefficient for a magnetic-measurement device that the trajectory was received from. 
     
     
         5 . The method of  claim 1 , wherein each of one or more of the correlation analyses comprises a similarity correlation analysis that comprises one or more of:
 normalized correlation;   cross correlation;   one or more spectral criteria functions; or   one or more difference criteria functions.   
     
     
         6 . The method of  claim 1 , wherein the magnetic measurements comprise measurements of magnetic susceptibility or magnetic conductivity. 
     
     
         7 . The method of  claim 1 , wherein the magnetic measurements comprise measurements of a magnetic field. 
     
     
         8 . The method of  claim 1 , wherein incorporating portions of the trajectories into the geomagnetic map comprises creating one or more portions of the geomagnetic map. 
     
     
         9 . The method of  claim 1 , wherein incorporating portions of the trajectories into the geomagnetic map comprises updating one or more portions of the geomagnetic map. 
     
     
         10 . The method of  claim 1 , wherein:
 one or more of the correlation analyses on one or more of the trajectories account for errors in the trajectories; and   one or more of the errors: 
 comprise noise; 
 are known; 
 are in one or more of the magnetic measurements in the trajectories; or 
 are in one or more determined locations where one or more of the magnetic measurements in the trajectories were made. 
   
     
     
         11 . The method of  claim 1 , wherein each of one or more of the correlation analyses comprises determining a correspondence between different gradient profiles associated with the magnetic measurements. 
     
     
         12 . The method of  claim 1 , wherein incorporating portions of the trajectories into the geomagnetic map comprises updating one or more trust levels associated with one or more portions of the geomagnetic map. 
     
     
         13 . One or more computer-readable non-transitory storage media embodying software that is operable when executed to:
 access a geomagnetic map that incorporates one or more portions of one or more trajectories from one or more magnetic-measurement devices comprising magnetic measurements in an area collected by the magnetic-measurement devices over a period of time, wherein the portions of the trajectories were incorporated into the magnetic map based on similarities in the trajectories determined at least in part by one or more correlation analyses performed on at least portions of the trajectories; and   perform localization or navigation using the geomagnetic map.   
     
     
         14 . The media of  claim 13 , wherein, to perform the correlation analyses and incorporate into the geomagnetic map portions of the trajectories, the software is operable when executed to:
 for each of one or more portions of one or more of the trajectories: 
 compare the portion of the trajectory with a corresponding portion of a baseline magnetic map according to a correlation analysis to determine similarity between the portion of the trajectory and the corresponding portion of the baseline magnetic map; and 
 store the portion of the trajectory based on the determined similarity between the portion of the trajectory and the corresponding portion of the baseline magnetic map; for each of one or more of the stored portions of the trajectories: 
 compare the portion of the trajectory with one or more corresponding other ones of the stored portions of the trajectories according to a correlation analysis to determine similarity between it and the corresponding other ones of the stored portions of the trajectories; and 
 continue to store the portion of the trajectory based on the determined similarity between the portion of the trajectory and the corresponding other ones of the stored portions of the trajectories; and 
   for each of one or more of the portions of the trajectories that is still stored, further continue to store the portion of the trajectory based on a weighting of the portion of the trajectory.   
     
     
         15 . The media of  claim 14 , wherein:
 the geomagnetic map comprises the baseline geomagnetic map; and   the baseline geomagnetic map comprises an Earth Magnetic Anomaly Grid with 2-arc-minute resolution (EMAG2) model.   
     
     
         16 . The media of  claim 14 , wherein the weighting of the portion of the trajectory is based at least in part on a trust coefficient for a magnetic-measurement device that the trajectory was received from. 
     
     
         17 . The media of  claim 13 , wherein each of one or more of the correlation analyses comprises a similarity correlation analysis that comprises one or more of:
 normalized correlation;   cross correlation;   one or more spectral criteria functions; or   one or more difference criteria functions.   
     
     
         18 . The media of  claim 13 , wherein the magnetic measurements comprise measurements of magnetic susceptibility or magnetic conductivity. 
     
     
         19 . The media of  claim 13 , wherein the magnetic measurements comprise measurements of a magnetic field. 
     
     
         20 . The media of  claim 13 , wherein incorporating portions of the trajectories into the geomagnetic map comprises creating one or more portions of the geomagnetic map. 
     
     
         21 . The media of  claim 13 , wherein incorporating portions of the trajectories into the geomagnetic map comprises updating one or more portions of the geomagnetic map. 
     
     
         22 . The media of  claim 13 , wherein:
 one or more of the correlation analyses on one or more of the trajectories account for errors in the trajectories; and   one or more of the errors: 
 comprise noise; 
 are known; 
 are in one or more of the magnetic measurements in the trajectories; or 
 are in one or more determined locations where one or more of the magnetic measurements in the trajectories were made. 
   
     
     
         23 . The media of  claim 13 , wherein each of one or more of the correlation analyses comprises determining a correspondence between different gradient profiles associated with the magnetic measurements. 
     
     
         24 . The media of  claim 13 , wherein incorporating portions of the trajectories into the geomagnetic map comprises updating one or more trust levels associated with one or more portions of the geomagnetic map. 
     
     
         25 . A system comprising:
 one or more processors; and   one or more computer-readable non-transitory storage media coupled to one or more of the processors and comprising instructions operable when executed by one or more of the processors to cause the system to: 
 access a geomagnetic map that incorporates one or more portions of one or more trajectories from one or more magnetic-measurement devices comprising magnetic measurements in an area collected by the magnetic-measurement devices over a period of time, wherein the portions of the trajectories were incorporated into the magnetic map based on similarities in the trajectories determined at least in part by one or more correlation analyses performed on at least portions of the trajectories; and 
 perform localization or navigation using the geomagnetic map. 
   
     
     
         26 . The system of  claim 25 , wherein, to perform the correlation analyses and incorporate into the geomagnetic map portions of the trajectories, the one or more processors are operable when executing the instructions to cause the system to:
 for each of one or more portions of one or more of the trajectories: 
 compare the portion of the trajectory with a corresponding portion of a baseline magnetic map according to a correlation analysis to determine similarity between the portion of the trajectory and the corresponding portion of the baseline magnetic map; and 
 store the portion of the trajectory based on the determined similarity between the portion of the trajectory and the corresponding portion of the baseline magnetic map; for each of one or more of the stored portions of the trajectories: 
 compare the portion of the trajectory with one or more corresponding other ones of the stored portions of the trajectories according to a correlation analysis to determine similarity between it and the corresponding other ones of the stored portions of the trajectories; and 
 continue to store the portion of the trajectory based on the determined similarity between the portion of the trajectory and the corresponding other ones of the stored portions of the trajectories; and 
   for each of one or more of the portions of the trajectories that is still stored, further continue to store the portion of the trajectory based on a weighting of the portion of the trajectory.   
     
     
         27 . The system of  claim 26 , wherein:
 the geomagnetic map comprises the baseline geomagnetic map; and   the baseline geomagnetic map comprises an Earth Magnetic Anomaly Grid with 2-arc-minute resolution (EMAG2) model.   
     
     
         28 . The system of  claim 26 , wherein the weighting of the portion of the trajectory is based at least in part on a trust coefficient for a magnetic-measurement device that the trajectory was received from. 
     
     
         29 . The system of  claim 25 , wherein each of one or more of the correlation analyses comprises a similarity correlation analysis that comprises one or more of:
 normalized correlation;   cross correlation;   one or more spectral criteria functions; or   one or more difference criteria functions.   
     
     
         30 . The system of  claim 25 , wherein the magnetic measurements comprise measurements of magnetic susceptibility or magnetic conductivity. 
     
     
         31 . The system of  claim 25 , wherein the magnetic measurements comprise measurements of a magnetic field. 
     
     
         32 . The system of  claim 25 , wherein incorporating portions of the trajectories into the geomagnetic map comprises creating one or more portions of the geomagnetic map. 
     
     
         33 . The system of  claim 25 , wherein incorporating portions of the trajectories into the geomagnetic map comprises updating one or more portions of the geomagnetic map. 
     
     
         34 . The system of  claim 25 , wherein:
 one or more of the correlation analyses on one or more of the trajectories account for errors in the trajectories; and   one or more of the errors: 
 comprise noise; 
 are known; 
 are in one or more of the magnetic measurements in the trajectories; or 
 are in one or more determined locations where one or more of the magnetic measurements in the trajectories were made. 
   
     
     
         35 . The system of  claim 25 , wherein each of one or more of the correlation analyses comprises determining a correspondence between different gradient profiles associated with the magnetic measurements. 
     
     
         36 . The system of  claim 25 , wherein incorporating portions of the trajectories into the geomagnetic map comprises updating one or more trust levels associated with one or more portions of the geomagnetic map. 
     
     
         37 . A system comprising:
 means for accessing a geomagnetic map that incorporates one or more portions of one or more trajectories from one or more magnetic-measurement devices comprising magnetic measurements in an area collected by the magnetic-measurement devices over a period of time, wherein the portions of the trajectories were incorporated into the magnetic map based on similarities in the trajectories determined at least in part by one or more correlation analyses performed on at least portions of the trajectories; and   means for performing localization or navigation using the geomagnetic map.