Measuring Distance Traversed or Speed

Abstract

In one embodiment, an apparatus includes a first magnetometer that measures a magnetic field. The apparatus includes a second magnetometer that measures the magnetic field. The first magnetometer includes a first coordinate frame with a first x axis, a first y axis, and a first z axis. The second magnetometer includes a second coordinate frame with a second x axis, a second y axis, and a second z axis. Each of one or more of the second x axis, the second y axis, or the second z axis has a predetermined orientation relative to the first x axis, the first y axis, or the first z axis.

1 . An apparatus comprising:
 a first magnetometer operable to measure a magnetic field, wherein the first magnetometer comprises a first coordinate frame that comprises a first x axis, a first y axis, and a first z axis; and   a second magnetometer operable to measure the magnetic field, wherein:
 the second magnetometer comprises a second coordinate frame that comprises a second x axis, a second y axis, and a second z axis; and 
 each of one or more of the second x axis, the second y axis, or the second z axis has a predetermined orientation relative to the first x axis, the first y axis, or the first z axis. 
   
     
     
         2 . The apparatus of  claim 1 , wherein each of one or more of the orientations is predetermined by being measured. 
     
     
         3 . The apparatus of  claim 1 , wherein each of one or more of the second x axis, the second y axis, or the second z axis is approximately 180° or 0° from the first x axis, the first y axis, or the first z axis. 
     
     
         4 . The apparatus of  claim 1 , wherein:
 the second x axis is approximately 180° from the first x axis;   the second y axis is approximately 180° from the first y axis; and   the second z axis is approximately 0° from the first z axis.   
     
     
         5 . The apparatus of  claim 1 , wherein the second magnetometer is positioned and oriented relative to the first magnetometer such that each of one or more of the second x axis, the second y axis, or the second z axis is approximately 180° from the first x axis, the first y axis, or the first z axis, respectively. 
     
     
         6 . The apparatus of  claim 1 , wherein the second magnetometer is positioned relative to the first magnetometer such that measurement of the magnetic field by the second magnetometer along each of one or more of the second x axis, the second y axis, or the second z axis is approximately equal to measurement of the magnetic field by the first magnetometer along each of one or more of the first x axis, the first y axis, or the first z axis, respectively. 
     
     
         7 . The apparatus of  claim 1 , wherein the first and second magnetometers are arranged on a plane. 
     
     
         8 . The apparatus of  claim 1 , wherein:
 the first and second magnetometers are both arranged on a first facet of a three-dimensional; or   the first magnetometer is arranged on the first facet of the three-dimensional shape and the second magnetometer is arranged on a second facet of the three-dimensional shape.   
     
     
         9 . The apparatus of  claim 1 , further comprising a device that is operable to:
 navigate or localize using output of the first and second magnetometers; or   compile output of the first and second magnetometers for use in generating one or more portions of a magnetic map.   
     
     
         10 . The apparatus of  claim 1 , further comprising:
 a third magnetometer operable to measure the magnetic field, wherein the third magnetometer comprises a third coordinate frame that comprises a third x axis, a third y axis, and a third z axis; and   a fourth magnetometer operable to measure the magnetic field, wherein:
 the fourth magnetometer comprises a fourth coordinate frame that comprises a fourth x axis, a fourth y axis, and a fourth z axis; and 
 each of one or more of the fourth x axis, the fourth y axis, or the fourth z axis has a predetermined orientation relative to the third x axis, the third y axis, or the third z axis. 
   
     
     
         11 . The apparatus of  claim 10 , wherein each of one or more of the fourth x axis, the fourth y axis, or the fourth z axis is approximately 180° or 0° from the third x axis, the third y axis, or the third z axis. 
     
     
         12 . The apparatus of  claim 10 , wherein:
 the fourth x axis is approximately 180° from the third x axis;   the fourth y axis is approximately 180° from the third y axis; and   the fourth z axis is approximately 0° from the third z axis.   
     
     
         13 . The apparatus of  claim 10 , wherein the fourth magnetometer is positioned and oriented relative to the third magnetometer such that each of one or more of the fourth x axis, the fourth y axis, or the fourth z axis is 180° from the third x axis, the third y axis, or the third z axis, respectively. 
     
     
         14 . The apparatus of  claim 10 , wherein the fourth magnetometer is positioned relative to the third magnetometer such that measurement of the magnetic field by the fourth magnetometer along each of one or more of the fourth x axis, the fourth y axis, or the fourth z axis is approximately equal to measurement of the magnetic field by the third magnetometer along each of one or more of the third x axis, the third y axis, or the third z axis, respectively. 
     
     
         15 . The apparatus of  claim 10 , wherein the third and fourth magnetometers are arranged on a plane. 
     
     
         16 . The apparatus of  claim 15 , wherein:
 the first and second magnetometers are arranged along a first line on the plane;   the third and fourth magnetometers are positioned along a second line on the plane that is approximately perpendicular to the first line.   
     
     
         17 . The apparatus of  claim 16 , further comprising:
 a fifth magnetometer arranged on the plane and positioned along a third line on the plane and operable to measure the magnetic field, wherein the fifth magnetometer comprises a fifth coordinate frame that comprises a fifth x axis, a fifth y axis, and a fifth z axis;   a sixth magnetometer arranged on the plane and positioned along a third line on the plane and operable to measure the magnetic field, wherein:
 the sixth magnetometer comprises a sixth coordinate frame that comprises a sixth x axis, a sixth y axis, and a sixth z axis; and 
 each of one or more of the sixth x axis, the sixth y axis, or the sixth z axis has a predetermined orientation relative to the fifth x axis, the fifth y axis, or the fifth z axis; 
   a seventh magnetometer arranged on the plane and positioned along a fourth line on the plane and operable to measure the magnetic field, wherein the seventh magnetometer comprises a seventh coordinate frame that comprises a seventh x axis, a seventh y axis, and a seventh z axis; and   an eighth magnetometer arranged on the plane and positioned along a fourth line on the plane and operable to measure the magnetic field, wherein:
 the eighth magnetometer comprises an eighth coordinate frame that comprises an eighth x axis, an eighth y axis, and an eighth z axis; and 
 each of one or more of the eighth x axis, the eighth y axis, or the eighth z axis has a predetermined orientation relative to the seventh x axis, the seventh y axis, or the seventh z axis; 
   wherein:
 the third line is approximately perpendicular to the fourth line; and 
 there is an approximately 45° angle between first line and the third line. 
   
     
     
         18 . The apparatus of  claim 10 , wherein:
 the first and second magnetometers are both arranged on a first facet of a three-dimensional shape and the third and fourth magnetometers are both arranged on a second facet of the three-dimensional shape; or   the first magnetometer is arranged on the first facet of the three-dimensional shape, the second magnetometer is arranged on the second facet of the three-dimensional shape, the third magnetometer is arranged on a third facet of the three-dimensional shape, and the fourth magnetometer is arranged on a fourth facet of the three-dimensional shape.   
     
     
         19 . The apparatus of  claim 10 , further comprising a device that is operable to:
 navigate or localize using output of the first, second, third, and fourth magnetometers; or   compile output of the first, second, third, and fourth magnetometers for use in generating one or more portions of a magnetic map.   
     
     
         20 . A method comprising:
 receiving output from a sensor set comprising:
 a first magnetometer operable to measure a magnetic field, wherein the first magnetometer comprises a first coordinate frame that comprises a first x axis, a first y axis, and a first z axis; and 
 a second magnetometer operable to measure the magnetic field, wherein:
 the second magnetometer comprises a second coordinate frame that comprises a second x axis, a second y axis, and a second z axis; and 
 each of one or more of the second x axis, the second y axis, or the second z axis has a predetermined orientation relative to the first x axis, the first y axis, or the first z axis; and 
 
   navigating or localizing using the output or compiling the output for use in generating one or more portions of a magnetic map.   
     
     
         21 . The method of  claim 20  wherein each of one or more of the second x axis, the second y axis, or the second z axis is approximately 180° or 0° from the first x axis, the first y axis, or the first z axis. 
     
     
         22 . The method of  claim 20 , wherein:
 the second x axis is approximately 180° from the first x axis;   the second y axis is approximately 180° from the first y axis; and   the second z axis is approximately 0° from the first z axis.   
     
     
         23 . The method of  claim 20 , wherein the second magnetometer is positioned and oriented relative to the first magnetometer such that each of one or more of the second x axis, the second y axis, or the second z axis is approximately 180° from the first x axis, the first y axis, or the first z axis, respectively. 
     
     
         24 . The method of  claim 20 , wherein the second magnetometer is positioned relative to the first magnetometer such that measurement of the magnetic field by the second magnetometer along each of one or more of the second x axis, the second y axis, or the second z axis is approximately equal to measurement of the magnetic field by the first magnetometer along each of one or more of the first x axis, the first y axis, or the first z axis, respectively. 
     
     
         25 . The method of  claim 20 , wherein the first and second magnetometers are arranged on a plane. 
     
     
         26 . The method of  claim 20 , wherein:
 the first and second magnetometers are both arranged on a first facet of a three-dimensional; or   the first magnetometer is arranged on the first facet of the three-dimensional shape and the second magnetometer is arranged on a second facet of the three-dimensional shape.   
     
     
         27 . The method of  claim 20 , further comprising:
 a third magnetometer operable to measure the magnetic field, wherein the third magnetometer comprises a third coordinate frame that comprises a third x axis, a third y axis, and a third z axis; and   a fourth magnetometer operable to measure the magnetic field, wherein:
 the fourth magnetometer comprises a fourth coordinate frame that comprises a fourth x axis, a fourth y axis, and a fourth z axis; and 
 each of one or more of the fourth x axis, the fourth y axis, or the fourth z axis has a predetermined orientation relative to the third x axis, the third y axis, or the third z axis. 
   
     
     
         28 . The method of  claim 27 , wherein each of one or more of the fourth x axis, the fourth y axis, or the fourth z axis is approximately 180° or 0° from the third x axis, the third y axis, or the third z axis. 
     
     
         29 . The method of  claim 27 , wherein:
 the fourth x axis is approximately 180° from the third x axis;   the fourth y axis is approximately 180° from the third y axis; and   the fourth z axis is approximately 0° from the third z axis.   
     
     
         30 . The method of  claim 27 , wherein the fourth magnetometer is positioned and oriented relative to the third magnetometer such that each of one or more of the fourth x axis, the fourth y axis, or the fourth z axis is 180° from the third x axis, the third y axis, or the third z axis, respectively.