Patent Publication Number: US-11397080-B2

Title: Calibration system for sensors and cameras on vehicles

Description:
RELATED APPLICATIONS 
     This disclosure is a divisional of U.S. patent application Ser. No. 16/394,694 filed on Apr. 25, 2019, which issued as U.S. Pat. No. 10,627,226 on Apr. 21, 2020, which is a continuation of, and claims the benefit of priority to, U.S. patent application Ser. No. 15/396,099 filed on Dec. 30, 2016 which issued as U.S. Pat. No. 10,323,936 on Jun. 18, 2019, the disclosures of which are each incorporated herein in their entirety. 
    
    
     TECHNICAL FIELD 
     This disclosure relates generally to sensor calibration systems, and more particularly to systems for calibrating sensors on vehicles. 
     BACKGROUND 
     Cameras and other types of sensors have been used on vehicles to enable systems that act as driving aids, such as for safety, awareness, or comfort. For example, an adaptive cruise control system generally uses sensors to detect the proximity of another vehicle in order to adjust vehicle speed or maintain a set vehicle spacing. In another example, a lane departure warning system generally uses sensors to detect a location of a vehicle within a lane of traffic in order to provide a warning to the driver or execute an automatic correction in the event that the vehicle is straying from the lane of traffic. Automated or assisted driving systems generally use sensors to enable machine vision that is used to navigate the vehicle to a destination while avoiding obstacles and obeying traffic laws and procedures. The sensors for these types of systems are generally mounted on the vehicle at various locations and orientations so as to collect the data needed to operate the systems. 
     In order to operate effectively, however, data read by the sensors must be relatable to a known orientation and location on the vehicle. For example, if the sensor is not located on a portion of the body of the vehicle that is closest to an obstacle, than the distance between the sensor and the obstacle sensed by the sensor will not indicate the true proximity of the obstacle. A known location and orientation of a sensor on the body of the vehicle can be used with a sensor reading in order to determine a true distance between an obstacle and the body of the vehicle. 
     Thus, the accuracy and effectiveness of systems relying on sensors depends on the accuracy of the location and orientation information for the sensors on the body of the vehicle. Generally, sensors on a vehicle are mounted at known locations relative to defined points such as an axle or wheel, and are oriented relative to a “thrust line” of the vehicle. The thrust line of a vehicle extends forwardly from a point of intersection of the rear transverse axis of the rear wheels and the longitudinal center line of the vehicle at an angle to the center line. The angle that the thrust line makes with respect to the center line of the vehicle is determined by the toe of the rear wheels, and is generally relatively small; for example, as close to zero as possible. 
     A calibration process is customarily used in order to determine or validate the location and orientation of a sensor. Devices used for calibration generally include an alignment element such as a mirror or optical target mounted on a stand that is placed at a fixed location in front of the vehicle so that the target is within a line-of-sight of the sensor. Precise calibration requires that the alignment element is positioned and oriented accurately in front of the vehicle according to that vehicle&#39;s specific manufacturer&#39;s specifications. Each vehicle may include a multitude of different types of sensors at different locations. Further, depending on the manufacturer&#39;s specifications, the alignment element may have to be oriented accurately relative to the vehicle in up to six different degrees of freedom; e.g., distance in front of the vehicle, left-to-right centering, perpendicularity to the thrust line, height, orientation about a horizontal axis, and orientation about an axis along the thrust line. 
     As a result, the number and position of alignment elements needed to calibrate the sensors of different vehicles can vary drastically from manufacturer to manufacturer, and even from vehicle to vehicle. Thus, each manufacturer generally provides one or more separate calibration devices that include the alignment elements adapted to the vehicles they offer for sale. Conventionally, mechanics and service professionals that seek to cater to a wide variety of makes and models of vehicles need to obtain and use a multitude of different calibration devices, which are customarily costly, and which require significant training to operate and maintain. Therefore, reducing the number of calibration devices needed to cater to a wide variety of vehicles would be beneficial. 
     SUMMARY 
     In one or more embodiments, a sensor calibration kit or system according to this disclosure includes a calibration tool, a front wheel alignment post, a rear wheel alignment post, a central extension mount, a laser line unit, and a plurality of calibration targets. 
     In one or more embodiments, the calibration tool includes a vertical rail that defines a first rail axis, a vertically movable carriage assembly supported by the vertical rail and movable along the first rail axis and having a horizontal rail that defines a second rail axis transverse to the first rail axis, and a horizontally movable carriage assembly supported by the horizontal rail and movable along the second rail axis. The horizontally movable carriage assembly has a transverse mounting bar with a plurality of target mounts. Each target mount is configured to releasably support a respective calibration target. 
     In one or more embodiments, the transverse mounting bar includes a mounting rail that defines a third rail axis transverse to the first rail axis. The plurality of target mounts are supported by the mounting rail and movable along the third rail axis. 
     In one or more embodiments, the transverse mounting bar is pivotably mounted on the second carriage assembly so as to be pivotable about a pivot axis transverse to the third rail axis. 
     In one or more embodiments, the horizontally movable carriage assembly further includes a spring member positioned between the horizontally movable carriage assembly and the transverse mounting bar on a first side of the pivot axis and configured to exert a force acting on the transverse mounting bar in a first direction about the pivot axis, and an adjustment member positioned between the horizontally movable carriage assembly and the transverse mounting bar on a second side of the pivot axis opposite the first side and operable to counter-act the force of the spring member to set a pivot position of the transverse mounting bar about the pivot axis. 
     In one or more embodiments, the transverse mounting bar includes a first ruler oriented parallel to the third rail axis. 
     In one or more embodiments, the calibration tool further includes a second ruler oriented parallel to the first rail axis. 
     In one or more embodiments, the calibration tool further includes a base plate assembly supporting the vertical rail and including an alignment member configured to align the calibration tool with a predetermined reference point. 
     In one or more embodiments, the kit further includes a line laser unit that is configured to produce a line laser configured to align the calibration tool relative to at least one of a measurement axis, a measurement orientation, and a vehicle. 
     In one or more embodiments, the line laser unit is mountable on the second carriage at a first position whereat the line laser unit is configured to produce a laser line extending parallel to the third rail axis to identify a yaw angle for the plurality of target mounts relative to the first rail axis, and a second position whereat the line laser unit is configured to produce a laser line extending perpendicular to the third rail axis to identify a centerline of the calibration tool. 
     In one or more embodiments, in the first position, the line laser unit is on a top surface of the horizontally movable carriage assembly. In the second position, the line laser unit is on a front-facing side surface of the horizontally movable carriage assembly such that the horizontally movable carriage assembly is between the line laser unit and the vertical rail. 
     In one or more embodiments, the front wheel alignment includes a first adjustment target configured to locate the front wheel alignment post relative to a wheel well of a front wheel of the vehicle, and a first mount configured to removably mount the line laser unit in a third position whereat the line laser unit is configured to produce a line laser on the front wheel of the vehicle such that the front wheel alignment post can be aligned with a center of the front wheel. 
     In one or more embodiments, the rear wheel alignment post includes a second adjustment target configured to locate the rear wheel alignment post relative to a wheel well of a rear wheel of the vehicle, and a second mount configured to removably mount the line laser unit in a fourth position whereat the line laser unit is configured to produce a line laser on the first adjustment target, such that the rear wheel alignment post can be aligned with the front wheel alignment post. 
     In one or more embodiments, the front wheel alignment post includes a mounting point configured to receive a measuring tape. 
     In one or more embodiments the first adjustment target of the front wheel alignment post includes a first level, and the front wheel alignment post further includes a plurality of individually adjustable feet. 
     In one or more embodiments, the second adjustment mount of the rear wheel alignment post includes a second level, and the rear wheel alignment post further includes a plurality of individually adjustable feet. 
     In one or more embodiments, in the first position, the line laser unit is on a top surface of the horizontally movable carriage assembly. In the second position, the line laser unit is on a front-facing side surface of the horizontally movable carriage assembly such that the horizontally movable carriage assembly is between the line laser unit and the vertical rail. 
     In one or more embodiments, the kit further includes at least one safety cord that is assigned to at least one calibration target, and at least one of the plurality of target mounts is a magnetic mounting point configured to magnetically engage with the at least one calibration target. The safety cord is configured to engage with the at least one calibration target. 
     In one or more embodiments, the central extension mount is supported by the vertically movable carriage assembly so as to extend parallel to the first rail axis. The central extension mount is configured to removably receive a first portion of a first calibration target, and a central mount is positioned on the horizontally movable carriage assembly and configured to removably receive a second portion of the first calibration target so that the first calibration target is parallel to the first rail axis. 
     In one or more embodiments, different combinations and positions of the plurality of different calibration targets enables calibration of sensors on different vehicles based on predetermined specifications corresponding to the different vehicles. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a perspective view of an exemplary embodiment of a calibration tool for a sensor calibration kit according to this disclosure. 
         FIGS. 2A and 2B  depicts perspective view different exemplary embodiments of a base plate assembly for the calibration tool from  FIG. 1 . 
         FIGS. 3 and 4  depict perspective views of different portions of the calibration tool of  FIG. 1 . 
         FIG. 5  depicts an exploded perspective view of a vertically movable carriage from the calibration tool of  FIG. 1 . 
         FIGS. 6A, 6B, and 7  depict different perspective views of a horizontally movable carriage assembly for the calibration tool of  FIG. 1 . 
         FIGS. 8 and 9  depict a perspective view of different exemplary embodiments of a central extension mount for a sensor calibration kit according to this disclosure. 
         FIG. 10  depicts a perspective vie of an exemplary embodiment of a front wheel alignment post for a sensor calibration kit according to this disclosure. 
         FIG. 11  depicts a perspective vie of an exemplary embodiment of a rear wheel alignment post for a sensor calibration kit according to this disclosure. 
         FIGS. 12-26  depict different steps of an exemplary process for aligning the calibration tool of  FIG. 1  with a vehicle using the front wheel alignment post from  FIG. 10  and the rear wheel alignment post from  FIG. 11 . 
         FIG. 27  depicts a schematic of the locations of the calibration tool, first measurement post, and second measurement post relative to a vehicle achieved using the methodology of  FIGS. 15-25 . 
     
    
    
     DETAILED DESCRIPTION 
     For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiments illustrated in the drawings and described in the following written specification. It is understood that no limitation to the scope of the disclosure is thereby intended. It is further understood that the present disclosure includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles of the disclosure as would normally occur to one of ordinary skill in the art to which this disclosure pertains. 
     A sensor calibration system or kit according to this disclosure includes one or more parts usable for calibrating sensors and cameras on various makes and models of vehicles. 
       FIG. 1  depicts a perspective view of an exemplary embodiment of a sensor calibration tool  100  included in a sensor calibration system according to this disclosure. The calibration tool  100  includes a base plate assembly  102 , a vertical rail  104 , a vertically movable carriage assembly  106 , a transverse carriage assembly  108 , a first ruler  110 , and a line laser unit  112 . 
     The first ruler  110  extends parallel to the vertical rail  104 , and includes measurement markings. 
       FIG. 2A  depicts an exploded perspective view of the base plate assembly  102 . The base plate assembly  102  includes a base portion  114 , a plurality of elevated wheel mounts  116 , a plurality of wheels  118 , and a plurality of feet  120 . 
     The base portion  114  of the base plate assembly  102  includes a mounting region  124  and an alignment member  125 . The alignment member  125  is configured to position the base plate assembly  102  at a predetermined location on a surface on which the calibration tool  100  is located. In this embodiment, the alignment member  125  includes at least one aperture  122  and at least one locating member  126 , in this instance a rib  126  that runs along a central axis  128  of the base plate assembly  102 . 
     In this embodiment, the base plate assembly  102  includes four elevated wheel mounts  116 , although more and less wheel mounts are included in other embodiments. The plurality of elevated wheel mounts  116  are distributed around the base portion  114 . A respective wheel  118  is mounted to each of the elevated wheel mounts  116 . The wheels  118  are configured to enable a user to move the calibration tool  100 . 
     The plurality of feet  120  are mounted on the base portion  114  of the base plate assembly  102 , and each include a screw member  121  and a foot member  123 . The feet  120  are configured such that a first operation of a respective screw member  121  causes a corresponding foot member  123  to extend downwards toward a surface on which the calibration tool  100  is positioned and lift base portion  114  and the plurality of wheels  118  from off the surface. The feet  120  are further configured such that a second operation of the respective screw member  121  causes the corresponding foot member  123  to retract the foot member  123  and move the base portion  114  and the plurality of wheels  118  toward the surface. 
       FIG. 2B  depicts a perspective view of another embodiment of the base plate assembly  102  where the wheels  118  are omitted. In this embodiment, the screw members  121  are adjustment knobs  121 , and the locating member  126  is a pair of nubs  126  aligned with the central axis  128 . 
     As illustrated in  FIG. 3 , a lower end  130  of the vertical rail  104  is received in the mounting region  124  of the base plate assembly  102 . The vertical rail  104  defines a first rail axis  132 . A carriage base  136  of the vertically movable carriage assembly  106  ( FIG. 1 ) is supported by the vertical rail  104  so as to be movable along the first rail axis  132 . In  FIG. 3 , elements of the vertically movable carriage assembly  106  ( FIG. 1 ) other than the carriage base  136  are omitted. 
     In this embodiment, the carriage base  136  includes a locking handle  134  that is selectively actuatable. In an un-actuated position, the locking handle  134  is configured to hold the carriage base  136  at a fixed position along the vertical rail  104 . In an actuated position, the locking handle  134  is configured to release the carriage base  136  to move along the vertical rail  104 . In other embodiments, other types of locking mechanisms for holding the carriage base  136  in place are also contemplated such as, for example, a pin, screw, clip, rack-and-pinion, etc. 
       FIG. 4  depicts a perspective view of the vertically movable carriage assembly  106  and a backing plate  144  and a clamp member  146  of the transverse carriage assembly  108  mounted together with the vertical rail  104 . Elements of the transverse carriage assembly  108  other than the backing plate  144  and the clamp member  146  are omitted. 
     The vertically movable carriage assembly  106  includes the carriage base  136 , a back plate  138 , and a horizontal rail  140 .  FIG. 5  depicts an exploded view of the back plate  138  and horizontal rail  140 . As illustrated in  FIG. 4 , the back plate  138  is mounted on the carriage base  136 , and the horizontal rail  140  is mounted on the back plate  138  so that the back plate  138  is disposed between the horizontal rail  140  and the carriage base  136 . 
     The horizontal rail  140  defines a second rail axis  142  that is transverse to the first rail axis  132 . As used herein, the term “transverse” means not parallel, but does not require, for example, that different axes intersect. For instance, in  FIG. 4  the second rail axis  142  is laterally offset from the first rail axis by the thickness of the vertically movable carriage assembly  106 , and the axes  142  and  132  thus do not intersect while being non-parallel and thus transverse to each other. In some embodiments, however, axes that are transverse also intersect. The backing plate  144  of the transverse carriage assembly  108  is supported by the horizontal rail  140  so that the transverse carriage assembly  108  is movable along the second rail axis  142 . 
     As illustrated in the exploded view of  FIG. 6A , the transverse carriage assembly  108  includes the backing plate  144 , the clamp member  146 , a transverse mounting bar  148 , a pivot member  150 , a spring member  152 , and an adjustment member  153 . 
     The clamp member  146  is mounted on the backing plate  144  so that the backing plate  144  is disposed between the clamp member  146  and the horizontal rail  140 . The clamp member  146  defines a channel  155  running transverse to the first rail axis  132  and a pair of holes  154  aligned parallel to the first rail axis  132  to define a pivoting axis  156 . 
     The transverse mounting bar  148  includes a transverse rail  158 , a plurality of target mounts  160 , and a second ruler  161 , and also defines a pivoting hole  162 . The transverse rail  158  extends over substantially an entire length of the transverse mounting bar  148 . In this embodiment, the transverse rail  158  is depicted as separated into two parts on either side of the pivoting hole  162 , but in some embodiments, the transverse rail  158  is continuous, or is divided into additional segments. 
     The transverse mounting bar  148  is mounted in the channel  155  so that the pivoting hole  162  is aligned with the pair of holes  154  in the clamping member  146 . The pivot member  150 , in this embodiment a pin  150 , extends through the pair of holes  154  in the clamping member  146  and through the pivoting hole  162  in the transverse mounting bar  148  in order to mount the transverse mounting bar  148  in the clamping member  146  so as to be pivotable about the pivoting axis  156 . 
     The transverse rail  158  of the transverse mounting bar  148  defines a third rail axis  164  that is transverse to the first rail axis  132 . Pivoting the transverse mounting bar  148  about the pivot axis  156  adjusts a yaw angle  159  of the transverse mounting bar  148  relative to the first rail axis  132 . 
     The spring member  152  is disposed between the transverse mounting bar  148  and the clamping member  146  on a first side of the pivoting hole  162 , and the adjustment member  153 , in this embodiment an adjustment knob  152 , is disposed in the clamping member  146  on an opposite side of the pivoting hole  162 .  FIG. 6B  depicts a detail view of the adjustment member  153 . Operating the adjustment member  153  adjusts a position of a screw  155  that counter-acts a force of the spring member  152  ( FIG. 6A ) and sets a pivot position of the transverse mounting bar  148  about the pivoting axis  156 . 
       FIG. 6B  also illustrates a mounting bracket  174  that can be included with the sensor calibration kit. The mounting bracket  174  is mounted on the second carriage assembly  108 , and includes a top face  176  disposed on top of the clamping member  146 , and a front facing side  178  that closes off the channel  155  of the clamping member  146 . 
     The front facing side  178  is configured as a front laser unit mounting point  178 , and the top face  176  is configured as a top laser unit mounting point  176 . In  FIG. 6B , the line laser unit  112  is mounted on the top face  176  is configured as a top laser unit mounting point  176 , but the line laser unit  112  can be repositioned to other line laser mounting points, as discussed in further detail below.  FIG. 7  illustrates an example where the line laser unit  112  is mounted on the front laser unit mounting point  178 . 
       FIGS. 8 and 9  depict different exemplary embodiments of a central mount extension  184  that can also be included in the sensor calibration kit. In  FIG. 8 , the central mount extension  184  is mounted on the vertically movable carriage assembly  106  so as to extend parallel to the first rail axis  132 , and includes a top bracket  185  that is coplanar with the front facing side  178  of the mounting bracket  174 . The top bracket  185  is configured as a top central mount  186 . In this embodiment, the front facing side  178  is further configured as a target mount to receive a first portion  187  of a central calibration target  168  The top central mount  186  is configured to receive a second portion  189  of a calibration target  168  such that the calibration target  168  in  FIG. 10  is at an orientation running parallel to the first rail axis  132 . The embodiment in  FIG. 9  depicts is similar to the example illustrated in  FIG. 10 . In this embodiment, however, the central mount extension  184  is mounted on the vertical rail  104  instead of on the vertically movable carriage assembly  106 . 
     As discussed above, in order to calibrate sensors on a vehicle, a calibration tool is positioned and oriented at a predefined location relative to the vehicle. In other words, each manufacturer or each vehicle may include specifications that define a predetermined location and orientation for calibration targets needed to calibrate the sensors on a particular vehicle. In some embodiment, additional elements are included in the sensor calibration kit to facilitate locating and positioning the calibration tool  100  relative to a vehicle. 
       FIG. 10  depicts a front wheel alignment post  200  that facilitates locating the calibration device  100  ( FIG. 1 ) relative to a vehicle. The front wheel alignment post  200  includes a front alignment bar  202 , a first adjustment target  204 , a laser unit mounting bracket  206 , and a front post base plate  208 . 
     The front post base plate  208  includes a plurality of adjustable feet  210  and a ruler tape mount  212 . The adjustable feet  210  are operable to level the first post base plate  208 . The ruler tape mounting point  212  is configured to receive an end of a ruler tape, as discussed in more detail below. 
     The front alignment bar  202  is mounted on the front post base plate  208  so as to extend in a direction normal to the front post base plate  208 . The front wheel alignment post  200  defines a front post rail  216  that extends along the direction normal to the front post base plate  208 . 
     The first adjustment target  204  is supported by the front post rail  216  so as to be movable along the direction normal to the front post base plate  208 , and includes a locking knob  218  and a target region  220 . The locking knob  218  is operable to selectively fix the first adjustment target  204  in place along the front post rail  216  and enable the first adjustment target  204  to move along the front post rail  216 . The target region  220  includes a laser target  222  and a level  224 . The level  224 , in this embodiment a spirit level  224 , is usable with the plurality of adjustable feet  210  for leveling the first adjustment target member  204  of the front wheel alignment post  200 . The laser target  222  facilitates orienting a further measurement post, as discussed in further detail below. 
     The laser unit mounting bracket  206  is affixed to the front alignment bar  202 , and includes a first face  226  parallel to the first post base plate  208 . The first face  226  is configured as a first post laser unit mount  228  to receive the line laser unit  112  for locating the front wheel alignment post  200  relative to a front wheel of a vehicle, as discussed in further detail below. 
       FIG. 11  depicts a rear wheel alignment post  300  that facilitates locating the calibration device  100  relative to a vehicle. The rear wheel alignment post  300  includes a rear alignment bar  302 , a second adjustment target  304 , a laser unit mounting bracket  306 , and a rear post base plate  308 . 
     The rear post base plate  308  includes a plurality of adjustable feet  310 . The adjustable feet  310  are operable to level the second post base plate  308 . The rear alignment bar  302  is mounted on the rear post base plate  308  so as to extend in a direction normal to the second post base plate  308 . The rear alignment bar  302  defines a rear post rail  316  that extends along the direction normal to the rear post base plate  308 . 
     The second adjustment target  304  is supported by the rear post rail  316  so as to be movable along the direction normal to the rear post base plate  308 , and includes a locking knob  318  and a target region  320 . The locking knob  318  is operable to selectively fix the second adjustment target  304  in place along the rear post rail  316  and enable the second adjustment target  304  to move along the rear post rail  316 . The target region  320  includes a laser target  322 . 
     The laser unit mounting bracket  306  is affixed to the rear alignment bar  302 , and includes a first face  326  parallel to the second post base plate  308 . The first face  326  is configured as a rear post laser unit mount and includes a level  324 . The second post laser unit mount  328  is configured to receive the line laser unit  112  for locating the second measuring post  200  relative to the front wheel alignment post  200 , as discussed in further detail below. The level  324 , in this embodiment a spirit level  324 , is usable with the plurality of adjustable feet  310  for leveling the first face  326  of the rear wheel alignment post  300 . 
       FIGS. 12-21  illustrate various stages of an exemplary process of locating the calibration tool  100  relative to a vehicle  400  using the front wheel alignment post  200  and rear wheel alignment post  300 . 
       FIG. 12  depicts an image  502  in which the first adjustment target  204  is positioned along the front post rail  216  and the front wheel alignment post  200  is positioned at a front wheel  402  of the vehicle  400  such that the first adjustment target  204  abuts and is oriented perpendicularly to a wheel well  404  of the front wheel  402 . 
       FIG. 13  depicts an image  504  in which the first adjustment target  204  is leveled according to the level  224  by operating the plurality of adjustable feet  210  on the first measurement post  200 . 
       FIG. 14  depicts an image  506 , in which the laser line unit  112  is mounted on the first post laser unit mount  228  and operated to produce a laser line  406 . The front wheel alignment post  200  is then centered relative to the front wheel  402  such that the laser line  406  is centered with the front wheel  402 . 
       FIG. 15  depicts an image  508 , in which the rear wheel alignment post  300  is positioned at a rear wheel  410  of the vehicle  400  such that the second adjustment target  304  abuts and is oriented perpendicularly to a wheel well  412  of the rear wheel  410 . The laser line unit  112  is mounted on the second post laser unit mounting point  328 , and is leveled according to the level  324  by operating the plurality of adjustable feet  310  on the second measurement post  300 . 
       FIG. 16  depicts an image  510 , in which the laser line unit  112  is operated to produce a laser line  414 . The rear wheel alignment post  300  is then rotated so that the laser line  414  is centered on the first adjustment target member  204 . 
       FIG. 17  depicts an image  512 , in which a measuring tape  418  is mounted on the ruler tape mounting point  212  of the front wheel alignment post  200  in order to identify a first reference mark  420  using a distance predetermined according to the specifications corresponding to the vehicle  400 . In another embodiment, a surface on which the vehicle  400  is positioned includes markings for measuring distances, and is used instead of or in addition to the measuring tape  418 . Other measurement techniques are also contemplated. 
       FIG. 18  depicts an image  514 , whereby the process from images  502 ,  504 ,  506 ,  508 ,  510 , and  512  are repeated for the opposite side of the vehicle  400  in order to identify a second reference mark  422 . 
       FIG. 19  depicts an image  516 , in which a straight-edge tool  424 , such as a measuring tape or ruler, is used to identify a center reference mark  426  centered between the first reference mark  420  and the second reference mark  422 . 
       FIG. 20  depicts an image  518 A, in which the line laser unit is mounted on the top laser unit mount  188  of the mounting bracket  174  of the transverse carriage assembly  108  ( FIG. 6B ). The laser line unit  112  is then operated to produce a laser line  424  that intersects the aperture  122  in the base plate assembly  102  of the calibration tool  100 . The calibration tool  100  is then moved, via the plurality of wheels  118 , so that the central reference mark  426  is visible through the pair of apertures  122 , and such that the locating member  126  is centered on the central reference mark  426 . 
       FIG. 21  depicts an alternative positioning for the laser line unit  112  on the calibration tool  100 . The line laser unit  112  is mounted on the front facing side  178  of the mounting bracket  174 , and is operated to produce a laser line  190  aligned with a center of the calibration tool  100 . The laser line  190  can then be aligned with a central reference mark, such as the central reference  426  shown in  FIG. 20 . 
       FIG. 22  depicts an image  520 A, in which the plurality of feet  120  on the base  102  are operated to lift the wheels  118  of from the surface  427  and set a location of the calibration tool  100  that is centered on the central reference point. The laser line  424  indicates the yaw angle of the transverse mounting bar  148  relative to the reference marks  420 ,  422 , and  426 . The adjustment member  153  is then operated to adjust the yaw angle  159  ( FIG. 6A ) and pivot the transverse mounting bar  148  so that the transverse mounting bar  148  is aligned with the first reference mark  420 , central reference mark  426 , and the second reference mark  422 . 
       FIG. 23  depicts an image  520 B showing an alternative procedure to the procedure depicting in image  520 A for identifying the yaw angle  159  and aligning the transverse mounting bar  148 . A pair of plum bobs  430  are mounted on a pair of opposing mounting members  160  on the transverse mounting bar  148 . At least one of positions of the mounts  160 , the location of the calibration tool  100 , and the yaw angle  159  is adjusted to align the plum bobs  430  with the first reference mark  420  and the second reference mark  422 , respectively. 
     Once positioned and oriented based on the specifications provided for a particular vehicle  400 , the target mounts  160  are moved to locations predetermined by the specification by at least one of moving the vertically movable carriage assembly  106  to a predetermined position along the first rail axis  132 , moving the horizontally movable carriage assembly  108  to a predetermined position along the second rail axis  142 , and moving one or more of the target mounts  160  to predetermined positions along the third rail axis  164 . 
     As discussed above, the calibration tool  100  ( FIG. 1 ) is configured to receive various combinations of calibration target members at different positions based on the different specifications for different vehicles.  FIG. 24  depicts an example where a pair of calibration targets  168  are disposed at opposite ends of the transverse mounting bar  148 . 
     The plurality of target mounts  160  are mounted on the transverse rail  158  so as to be movable along the third rail axis  164 . Thus, the yaw angle  159  of the transverse mounting bar  148  is also a yaw angle  159  for the plurality of target mounts  160 . The second ruler  161  extends parallel to the third rail axis  164 , and includes measurement markings to facilitate locating positions for the plurality of target mounts  160  along the transverse rail  158 . Each of the plurality of target mounts  160  is configured to act as a respective mounting point to releasably mount a calibration target member. 
       FIG. 25  depicts another example where a calibration target  168  is mounted on the front facing side  178  of the mounting bracket  174 . 
       FIG. 26  depicts an exemplary calibration target member  168  mounted onto a target mount  160 . In this embodiment, the target mount  160  includes a magnetic material that defines a magnetic mount  170 , and also includes a safety cable  172 . The calibration target member  168  includes a metallic material, and is configured to magnetically adhere to the magnetic mount  170 . The magnetic adherence between the calibration target member  168  and the target mount  160  enables rapid installation and removal of different calibration target members from the calibration tool  100 . The safety cable  172  is configured to engage with the calibration target member  168  and catch the calibration target member  168  in the event of a failure of the magnetic adherence between the calibration target member  168  and the magnetic mounting point  170  of the target mount  160 . 
     In  FIG. 26 , the calibration target member  168  is depicted as having a substantially rectilinear shape. In other embodiments, calibration target members can have any arbitrary shape. In  FIG. 26 , the calibration target member  168  is also depicted as being mounted on a single target mount  160 . In some embodiments, a single calibration target member are mounted on a plurality of mounting elements, and in some embodiments, a plurality of calibration target elements are mounted on a single mounting element. In various embodiments target mounts  160  of various sizes and shapes are also contemplated. 
       FIG. 27  depicts a top view of the positions of the calibration tool  100 , first measuring posts  200  and second measuring posts  300  after being aligned according to the methodology discussed above. As illustrated in  FIG. 27 , the calibration tool  100  is located and oriented relative to not only the vehicle  400 , but also to a thrust line  450  of the vehicle. 
     It will be appreciated that variants of the above-described and other features and functions, or alternatives thereof, may be desirably combined into many other different systems, applications or methods. Various presently unforeseen or unanticipated alternatives, modifications, variations or improvements may be subsequently made by those skilled in the art that are also intended to be encompassed by the disclosure.