Calibration techniques for activity sensing devices

<u>BACKGROUND OF THE INVENTION</u>

Field of the Invention

0001The present invention relates to activity monitoring and, more particularly, to activity monitoring by portable electronic devices.

Description of the Related Art

0002A media player stores media assets, such as audio tracks, that can be played or displayed on the media player. One example of a portable media player is the iPod® media player, which is available from Apple Computer, Inc. of Cupertino, CA. Often, a media player acquires its media assets from a host computer that serves to enable a user to manage media assets. In managing media assets, a user can create playlists for audio tracks. These playlists can be created at the host computer. Media assets within the playlists can then be copied to the media player. As an example, the host computer can execute a media management application to acquire and manage media assets. One example of a media management application is iTunes® produced by Apple Computer, Inc.

0003Portable media players, such as MP3 players, are able to play music for users often via earphones or a headset. Typically, portable media players are dedicated to playing media. Lately, media players have been integrated into mobile telephones as well as personal information managers (or digital personal assistants). However, many users of portable media players utilize their media players in the context of exercising, such as at the gym or while running outdoors. Unfortunately, however, portable media players are not designed to assist the users in the context of their exercising. Although portable media players can play music for the users, there is traditionally no capability to provide any non-media information to the user.

0004One existing approach is to use a wristwatch including GPS technology to track distance of runs, but such lacks the ability to provide media playback. While GPS may not require a calibration operation, GPS technology itself is unable to provide high precision monitoring and is dependent on being able to interact in a wireless manner with satellites.

0005Another existing approach is a speedometer system that includes a watch worn on a user's wrist and a small foot worn device on the user's shoe. The speedometer system can provide the user with information concerning speed, pace, distance and calories while running or walking. The speedometer system requires that the user perform one or more calibration operations to enhance accuracy. The calibration operation requires that the user run on a track or treadmill for an accurate distance. Such calibration operations are not only burdensome on its users but also can often lack accuracy.

0006Recently, a MP3 player has been enhanced to support wireless communications, through a Bluetooth module, with a wireless speed and distance sensor that is coupled to the shoelaces of the user's shoe. The wireless speed and distance sensor operates as a pedometer and can wirelessly transmit data to the MP3 player. Such a system permits interaction between a MP3 player and a pedometer, which are conventionally separate devices. This system also requires that the user perform one or more calibration operations to enhance accuracy. Such calibration operations are not only burdensome on its users but also can often lack accuracy.

0007Regardless, there remains a need for improved accuracy of sensing systems for use in or with portable media players or other electronic devices so that users are able to monitor their exercise.

<u>SUMMARY OF THE INVENTION</u>

0008The invention relates to improved techniques and systems to calibrate an electronic device that is providing activity sensing. The activity being sensed can, for example, correspond to walking or running by a user. In one embodiment, calibration can be performed by a portable electronic device so that activity data it receives from a remote sensor device can be more accurately processed.

0009The improved techniques to calibrate can be used by a portable electronic device to monitor, process, present and manage data captured by a remote sensor. The portable electronic device can also offer a convenient user interface that can be visual and/or audio based, customized to a particular application, user-friendly and/or dynamic. The portable electronic device can pertain to a portable media player and thus also provide media playback.

0010The invention can be implemented in numerous ways, including as a method, system, device, apparatus (including graphical user interface), or computer readable medium. Several embodiments of the invention are discussed below.

0011As a method for calibrating an activity monitoring system associated with a user, one embodiment of the invention includes at least the acts of: providing the activity monitoring system with default calibration data; performing a first calibration to produce first modified calibration data, the first modified calibration data being derived from the default calibration data; and subsequently performing a second calibration to produce second modified calibration data, the second modified calibration data being derived from the first modified calibration data.

0012As a method for calibrating an activity monitoring system associated with a user, one embodiment of the invention includes at least the acts of: receiving a calibration request from the user; receiving an indication of a calibration distance; awaiting a calibration start indication before starting activity to be used for calibration; receiving activity data from an activity sensor associated with the activity monitoring system during the activity for calibration; estimating at least one of pace and distance based on the received activity data and an existing calibration model; awaiting receipt of a calibration stop indication; repeating the receiving and the estimating until the calibration stop indication is received; and modifying the existing calibration model based on at least the estimated distance from the estimating and the calibration distance.

0013As a method for operating an activity monitoring apparatus associated with a user utilizing at least one shoe, one embodiment of the invention includes at least the acts of: receiving shoe characteristic information pertaining to the shoe; and operating the activity monitoring apparatus based at least in part on the shoe characteristic information.

0014As a portable electronic device, one embodiment of the invention includes at least: a user interface for providing user input to the portable electronic device and user output from the portable electronic device; a calibration model; an activity application that operates to monitor a physiological characteristic of a user of the portable electronic device, the activity application receives sensor data acquired from a remote sensor associated with the user, and the activity application processes the sensor data in view of the calibration model; a calibration engine that operates to modify the calibration model in view of a calibration activity for which sensor data from the remote sensor is acquired and processed by the activity application or the calibration engine.

0015As a computer readable medium including at least computer program code for calibrating an activity monitoring system associated with a user, one embodiment of the invention includes at least: computer program code for performing a first calibration to produce first modified calibration data, the first modified calibration data being derived from existing calibration data; and computer program code for subsequently performing a second calibration to produce second modified calibration data, the second modified calibration data being derived from the first modified calibration data.

0016As a computer readable medium including at least computer program code for calibrating an activity monitoring system associated with a user, another embodiment of the invention includes at least: computer program code for receiving an indication of a calibration distance; computer program code for awaiting a start indication before starting activity to be used for calibration; computer program code for receiving activity data from an activity sensor associated with the activity monitoring system during the activity to be used for calibration; computer program code for estimating at least one of pace and distance based on the received activity data and an existing calibration model; computer program code for awaiting receipt of a stop indication that indicates the end of the activity to be used for calibration; and computer program code for modifying the existing calibration model based on at least the estimated distance and the calibration distance.

0017Other aspects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.

<u>BRIEF DESCRIPTION OF THE DRAWINGS</u>

0018The invention will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which:

0019<figref idref="f0001">FIG. 1</figref> is a block diagram of a sports monitoring system according to one embodiment of the invention.

0020<figref idref="f0002">FIG. 2</figref> is an activity monitoring system for an electronic device according to one embodiment of the invention.

0021<figref idref="f0003">FIG. 3</figref> is a flow diagram of a multi-speed calibration process according to one embodiment of the invention.

0022<figref idref="f0004">FIGs. 4A</figref> and <figref idref="f0005">4B</figref> are flow diagrams of a calibration model improvement process according to one embodiment of the invention.

0023<figref idref="f0006">FIG. 5</figref> illustrates a graph pertaining to walking calibration according to one embodiment of the invention.

0024<figref idref="f0007">FIGs. 6A</figref> and <figref idref="f0008">6B</figref> illustrate graphs pertaining to running calibration according to one embodiment of the invention.

0025<figref idref="f0009 f0010 f0011 f0012 f0013">FIGs. 7-19</figref> are exemplary screens that pertain to fine-tuning accuracy of an activity monitoring system.

0026<figref idref="f0014">FIG. 20</figref> is an activity monitoring system for an electronic device according to another embodiment of the invention.

<u>DETAILED DESCRIPTION OF THE INVENTION</u>

0027One aspect of the invention pertains to improved techniques to calibrate an electronic device that is providing activity sensing. The activity being sensed can, for example, correspond to walking or running by a user. In one embodiment, calibration can be performed by a portable electronic device so that activity data it receives from a remote sensor device can be more accurately processed.

0028The improved techniques to calibrate can be used by a portable electronic device to monitor, process, present and manage data captured by a remote sensor. The portable electronic device can also offer a convenient user interface that can be visual and/or audio based, customized to a particular application, user-friendly and/or dynamic. The portable electronic device can pertain to a portable media player and thus also provide media playback.

0029The invention is particularly well suited for use in monitoring sports-related data, such as exercise data (e.g., run data). However, it should be recognized that the invention is not limited to sports monitoring, but instead is applicable to any type of monitoring. For example, the monitoring can be any physiological monitoring of a person, who is typically the user of a portable electronic device.

0030Embodiments of the invention are discussed below with reference to <figref idref="f0001 f0002 f0003 f0004 f0005 f0006 f0007 f0008 f0009 f0010 f0011 f0012 f0013 f0014">FIGs. 1 - 20</figref>. However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these figures is for explanatory purposes as the invention extends beyond these limited embodiments.

0031<figref idref="f0001">FIG. 1</figref> is a block diagram of a sports monitoring system 100 according to one embodiment of the invention. The sports monitoring system 100 is an electronic system that enables sports related information to be acquired, stored, analyzed, presented and shared.

0032The sports monitoring system 100 includes a portable media device 102. The portable media device 102 is capable of storing and playing media for its user. For example, the portable media device 102 can output (e.g., play) audio or video. The sports monitoring system 100 also includes a sports device 104. The sports device 104 is, for example, a pedometer, a heart rate monitor, etc. The sports device 104 includes one or more sensors that acquire sports related data.

0033The sports device 104 also includes wireless transmission capability so that the sports related data can be transmitted to the portable media device 102. In particular, the portable media device 102 includes a wireless interface accessory 106. The wireless interface accessory 106 includes a wireless transceiver so that the wireless interface accessory 106 can receive the sports related data being transmitted by the sports device 104 by way of a wireless connection through a personal wireless network 108. The portable media device 102 can receive the sports related data from the sports device 104 via the wireless interface accessory 106 and can then operate to process and store the sports related data at the portable media device 102.

0034The sports monitoring system 100 also includes a personal computer 110. The portable media device 102 can be electrically connected to the personal computer 110 by way of a cable 112. The cable 112 can, for example, be a Firewire or USB cable. Alternatively, the cable 112 can be replaced with a wireless link. Although the portable media device 102 is not normally electrically connected to the personal computer 110, the electrical connection, when present, facilitates information exchange between the portable media device 102 and the personal computer 110.

0035The personal computer 110 includes a media management application 114. The media management application 114, in one embodiment, can not only manage the media assets stored on the personal computer 110, but can also store and manage sports related data. In one embodiment, the media management application 114 can operate to cause the sports related data stored on the portable media device 102 to be copied to the personal computer 110. Thereafter, the sports related data can be analyzed at the personal computer 110 and/or made available to the user of the personal computer 110. In addition, the sports monitoring system 100 can facilitate the personal computer 110 coupling to a data network 116. The data network 116 can represent a global or wide area network, such as the World Wide Web (or the Internet). When the personal computer 110 is coupled to the data network 116, the sports related data present at the personal computer 110 can be transferred to a sports management server 118. At the sports management server 118, the sports related data can be further analyzed and/or processed to facilitate usefulness of the data. The sports management server 118 supports storage and analysis of sports related data from a large number of different portable media devices and/or personal computers. Hence, the sports management server 118 can also compare the sports related data from different users. The sports management server 118 can also provide a website that can be accessed by a network browser operating on the personal computer 110 or other computing device to access sports related information or other information made available via the website.

0036The sports monitoring system 100 can also support one or more remote controllers (not shown). A remote controller can also communicate with a portable media device 102 via the wireless interface accessory 106. The remote controller may require it be paired or linked with the wireless interface accessory 106 or the portable media device 102.

0037The sports device 104 illustrated in <figref idref="f0001">FIG. 1</figref> can take a variety of different forms. In one embodiment, the sports device is a sensor-based device. One example of a sensor-based device is a pedometer.

0038Although the sports monitoring system 100 illustrated in <figref idref="f0001">FIG. 1</figref> provides the wireless interface accessory 106 apart from the media device 102, in another embodiment, the functionality (e.g., wireless interface) provided by the wireless interface accessory 106 can be provided by the media device 102 itself.

0039<figref idref="f0002">FIG. 2</figref> is an activity monitoring system 200 for an electronic device according to one embodiment of the invention. The electronic device is, for example, a portable media device, such as the portable media device 102 illustrated in <figref idref="f0001">FIG. 1</figref>. The activity monitoring system 200 includes an activity application 202. The activity application 202 is a software program that operates on the electronic device. In one example, the activity application 202 can facilitate and manage workout monitoring of workouts that are performed by a user of the electronic device.

0040The activity monitoring system 200 also includes a user interface 204. The user interface 204 can be utilized to provide user inputs that can be used by the activity application 202. For example, one particular user input is a request for calibration. <figref idref="f0009 f0010 f0011">FIGs. 7-15</figref>, which are discussed below, illustrate exemplary screens of a graphical user interface that can enable a user to request calibration. When the activity application 202 receives a request for calibration, the activity application 202 starts a calibration process that is performed by the activity application 202 together with a calibration engine 206. The calibration process makes use of activity sensor data 208 that is supplied to the electronic device from an activity sensor. The activity sensor is typically separate from the electronic device. The activity sensor transmits activity sensor data 208 to the electrical device. At the electrical device, the activity application 202 can receive the activity sensor data 208.

0041The activity application 202 can process the activity sensor data in conjunction with a calibration model 210. The calibration model 210 is a stored calibration model for use by the electronic device. In one embodiment, the calibration model 210 is customized to the user of the electronic device. In addition, the activity application 202 provides processed activity data as well as the calibration model 210 to the calibration engine 206. The calibration engine 206 can then determine, typically at the end of the calibration process, whether and how to modify the calibration model 210 so that the activity application 202 is able to more accurately interpret the activity sensor data 208. In other words, the calibration engine 206 operates to cause the calibration model 210 to be modified so as to better fit the characteristics of the user of the electronic device. Either the calibration engine 206 or the activity application 202 can change the calibration model 210. Thereafter, the activity application 202 is able to provide more accurate activity monitoring.

0042<figref idref="f0003">FIG. 3</figref> is a flow diagram of a multi-speed calibration process 300 according to one embodiment of the invention. The multi-speed calibration process 300 is, for example, performed by an electronic device, such as the portable media device 102 illustrated in <figref idref="f0001">FIG. 1</figref>. More particularly, the multi-speed calibration process 300 can be performed by the activity monitoring system 200 illustrated in <figref idref="f0002">FIG. 2</figref>.

0043The multi-speed calibration process 300 begins with a decision 302. The decision 302 determines whether an activity monitoring system is to be calibrated at a slower pace. In this embodiment, the activity monitoring system can be calibrated at a slower pace as well as a faster pace. Typically, the pace pertains to walking or running that is performed by the user during a calibration process. When the decision 302 determines that the activity monitoring system is to be calibrated at a slower pace, calibration is performed 304 to modify a calibration model. The calibration model being modified is either a default calibration model or a previously determined calibration model.

0044Following the block 304, or following the decision 302 when the activity monitoring system is not to be calibrated at a slower pace, a decision 306 determines whether the activity monitoring system is to be calibrated at a faster pace. When the decision 306 determines that the activity monitoring system is to be calibrated at a faster pace, calibration is performed 308 to modify the calibration model.

0045Following the block 308, or following the decision 306 when the activity monitoring system is not to be calibrated at a faster pace, the activity monitoring system is operated 310 in accordance with the modified calibration model. Typically, following calibration, the calibration model is improved as compared to the calibration model prior to such additional calibration. As a result, the activity monitoring performed by the activity monitoring system is more accurate. For example, when the activity being monitored is walking or running, the activity monitoring system using the modified calibration model is able to more accurately determine characteristics of the walking or running, such as distance traveled, pace, etc.

0046The multi-speed calibration process 300 indicates that calibration can be performed at not only a slower pace but also a faster pace. The advantage of calibrating at a slower speed as well as a faster speed is that the calibration becomes more accurate and thus more reliable. However, it should be understood that in some embodiments, only one calibration need be performed. It should also be understood that in some embodiments, a calibration at one pace could be performed at one point in time, and calibration at another different pace could be performed sometime significantly later (e.g., day, week or months later).

0047<figref idref="f0004">FIGs. 4A</figref> and <figref idref="f0005">4B</figref> are flow diagrams of a calibration model improvement process 400 according to one embodiment of the invention. The calibration model improvement process 400 is, for example, performed by an electronic device, such as the portable media device 102 illustrated in <figref idref="f0001">FIG. 1</figref>. More particularly, the calibration model improvement process 400 can be performed by the activity monitoring system 200 illustrated in <figref idref="f0002">FIG. 2</figref>.

0048The calibration model improvement process 400 begins with a decision 402 that determines whether a calibration request has been received. In one embodiment, the calibration request can be initiated by a user of the electronic device. When the decision 402 determines that a calibration request has not been received, the calibration model improvement process 400 awaits such a request. On the other hand, when the decision 402 determines that a calibration request has been received, the calibration model improvement process 400 continues. In other words, the calibration model improvement process 400 is effectively invoked when the calibration request is received.

0049When the calibration model improvement process 400 continues, a user entry of a calibration distance is received 404. As an example, the user can interact with a user interface of the electronic device to enter or select a calibration distance (i.e., predetermined calibration distance). A decision 406 then determines whether calibration has been started. For example, the user of the electronic device can initiate calibration through user action, such as via the user interface of the electronic device. When the decision 406 determines that calibration has not been started, the calibration model improvement process 400 awaits start of the calibration.

0050Once the decision 406 determines that calibration is to be started, an elapsed distance is set 408 to zero. The elapsed distance is the distance that the user covers during the calibration process. The calibration process is typically associated with a walk or run by the user. Hence, the elapsed distance can thus be a distance to be run or walked during the calibration process.

0051Next, a decision 410 determines whether there is new activity data. The activity data, as noted above, with respect to <figref idref="f0002">FIG. 2</figref>, can be provided by an activity sensor that is separate from the electronic device (e.g., the portable media device 102). When the decision 410 determines that new activity data is present, a contact time is extracted 412 from the new activity data. Contact time is the time that the user's shoe is in contact with the ground as the user runs or walks. Using the contact time, estimates of current pace and elapsed distance can be updated 414 during the calibration process. The calibration model is used to acquire the current pace and elapsed distance from the new activity data (e.g., contact time).

0052A decision 416 then determines whether the pace for the calibration process, i.e., walk or run, is too varied. When the pace is determined to be too varied, then the calibration process is deemed unreliable. Hence, in such case, the calibration process is aborted 418. Alternatively, when the decision 416 determines that the pace is not too varied, a decision 420 determines whether a calibration complete indication has been received. In one embodiment, a user can interact with the electronic device to initiate a calibration complete indication. For example, the user can interact with the electronic device to signal that a predetermined calibration distance has been run or walked. In any case, when the decision 420 determines that a calibration complete indication has not been received, the calibration model improvement process 400 returns to repeat the decision 410 and subsequent blocks so that new activity data can be similarly processed.

0053On the other hand, when the decision 420 determines that a calibration complete indication has been received, an accuracy ratio is determined 422 based on actual distance and estimated elapsed distance. The actual distance is the distance the user ran or walked for the calibration process. Typically, the actual distance is the predetermined calibration distance that is chosen in block 404. For example, one common calibration distance is 400 meters, since such can be readily found at a 400 meters oval track. The estimated elapsed distance is the accumulated elapsed distances during the calibration process (block 414) as acquired using the electronic device.

0054Next, a decision 424 then determines whether the accuracy ratio is greater than (or less than) a threshold. In one implementation, the determination can determine whether the accuracy ratio is greater than a maximum threshold or less than a minimum threshold. These thresholds can be used to ensure that the accuracy ratio is not too excessive (e.g., too far from unity). A large or small accuracy ratio typically indicates that the calibration process was defective in some way. Hence, it is desirable to avoid using the data resulting from a calibration process that was defective. Hence, when the decision 424 determines that the accuracy ratio is greater than a threshold, the calibration process is aborted 418. Alternatively, when the decision 424 determines that the accuracy ratio is not greater than (less than) a threshold, then the calibration model is modified 426 based on the accuracy ratio. Following the block 426 as well as following the block 418, the calibration model improvement process 400 ends.

0055Although the calibration model improvement process 400 operates to receive a calibration request from a user to initiate the calibration process, it should be understood that in another embodiment, the activity data could be first captured and then subsequently a user could initiate the calibration process using the activity that was previously captured.

0056<figref idref="f0006">FIG. 5</figref> illustrates a graph pertaining to walking calibration according to one embodiment of the invention. The x-axis of the graph is for ground contact time (Tc) in milliseconds (ms), and the y-axis of the graph is for pace (P) in minutes/mile. The graph plots a calibration model. The calibration model is a line defined by two points, a lower model point (M1) and an upper model point (M2). The solid line represents an existing calibration model. The dotted line represents a modified calibration model that results following the walking calibration. In one embodiment, the modification (e.g., modifying 426) to the calibration model involves moving the upper model point (M2). The upper model point (M2) is moved left or right such that the ratio of the slope of the existing calibration line to slope of the modified calibration line is the same as the accuracy ratio (AR). The following equation is used to acquire the new upper model point (M2) for the calibration model: <maths id="math0001"><math display="block"><mi>Tc</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo>⁢</mo><mi mathvariant="normal">a</mi><mo mathvariant="normal">=</mo><mfenced><mn mathvariant="normal">1</mn><mo mathvariant="normal">-</mo><mi>AR</mi></mfenced><mo mathvariant="normal">*</mo><mi>Tc</mi><mo>⁢</mo><mn mathvariant="normal">1</mn><mo mathvariant="normal">+</mo><mi>AR</mi><mo mathvariant="normal">*</mo><mi>Tc</mi><mo>⁢</mo><mn mathvariant="normal">2.</mn></math><img file="EP2575326A1_D0001.tif" /></maths>

0057In effect, by moving the upper model point (M2) of the calibration model, the calibration pivots about the lower model point (M1). Although <figref idref="f0006">FIG. 5</figref> pertains to walking calibration, the same calibration approach can be used for a running calibration. Preferably, the calibration lines for running and walking are separate lines.

0058In one embodiment, the user is recommended to perform a walking calibration and a running calibration. These different calibrations can be performed separately one after another on the same day or they can be performed many days apart. As an example, the walking calibration might move the upper model point (M2). In effect, by moving the upper model point (M2) of the calibration model, the calibration line pivots about the lower model point (M1).

0059Besides the calibration process illustrated in <figref idref="f0006">FIG. 5</figref> in which one point of a line representing a calibration model is moved to render the calibration model more accurate, another calibration process can move more than one point (e.g., two points) of a line representing a calibration model.

0060<figref idref="f0007">FIGs. 6A</figref> and <figref idref="f0008">6B</figref> illustrate graphs pertaining to running calibration according to one embodiment of the invention. The running calibration is done in two stages or legs. The user will run at different paces during the different stages or legs. One of the paces is deemed a faster pace, and the other of the paces is deemed a slower pace.

0061In <figref idref="f0007">FIG. 6A</figref>, the graph illustrates calibration following a first stage or leg. The calibration process here is generally the same as that discussed above with reference to <figref idref="f0006">FIG. 5</figref>. Typically, this leg would correspond to a slower pace run. In addition, the average contact time (Tc_leg1) for the first stage or leg is stored.

0062In <figref idref="f0008">FIG. 6B</figref>, the graph illustrates calibration following a second stage or leg. In one embodiment, the modification (e.g., modifying 426) to the calibration model involves moving both the upper model point (M2) and the lower model point (M2). The average contact time (Tc_leg2) for the second stage or leg is determined from the user performance (i.e., activity data) of the second stage or leg of the calibration process as generally discussed above with regard to determining the average contact time (Tc_leg1). If the average contact time (Tc_leg2) for the second stage or leg is too close to the average contact time (Tc_leg1) for the first stage or leg, then the average contact time (Tc_leg2) for the second stage or leg can be discarded and the calibration completed based on the calibration information for the first stage or leg.

0063On the other hand, if the average contact time (Tc_leg2) for the second stage or leg is not too close to the average contact time (Tc_leg1) for the first stage or leg, then the calibration process is completed using information from the second stage or leg. The lower model point (M1) is moved left or right such that the ratio of the slope of the existing calibration line to the slope of the modified calibration line is the same as the accuracy ratio (AR), while also insuring that the average contact time (Tc_leg1) for the first stage or leg remains on the modified calibration line. The following equations can be used to acquire the new lower model point (M1) for the calibration model: <maths id="math0002"><math display="block"><mi>Tc</mi><mo>⁢</mo><mn mathvariant="normal">1</mn><mo>⁢</mo><mi mathvariant="normal">b</mi><mo mathvariant="normal">=</mo><mfenced><mi mathvariant="normal">k</mi><mo mathvariant="normal">*</mo><mi>Tc_leg</mi><mo>⁢</mo><mn mathvariant="normal">1</mn><mo mathvariant="normal">-</mo><mi>AR</mi><mo mathvariant="normal">*</mo><mi>Tc_leg</mi><mo>⁢</mo><mn mathvariant="normal">2</mn></mfenced><mo mathvariant="normal">/</mo><mfenced><mi mathvariant="normal">k</mi><mo mathvariant="normal">-</mo><mi>AR</mi></mfenced><mo mathvariant="normal">,</mo></math><img file="EP2575326A1_D0002.tif" /></maths> where <maths id="math0003"><math display="block"><mi mathvariant="normal">k</mi><mo mathvariant="normal">=</mo><mfenced><mi>Tc_leg</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo mathvariant="normal">-</mo><mi>Tc</mi><mo>⁢</mo><mn mathvariant="normal">1</mn></mfenced><mo mathvariant="normal">/</mo><mfenced><mi>Tc_leg</mi><mo>⁢</mo><mn mathvariant="normal">1</mn><mo mathvariant="normal">-</mo><mi>Tc</mi><mo>⁢</mo><mn mathvariant="normal">1</mn></mfenced><mn mathvariant="normal">.</mn></math><img file="EP2575326A1_D0003.tif" /></maths>

0064In effect, by moving the lower model point (M1) of the calibration model, the calibration pivots about a point on the line that corresponds to the average contact time (Tc_leg1) for the first stage or leg. The calibration process can also check that Tc1b is within reasonable range limits for contact times. The reasonable range limits can be empirically determined from user population studies.

0065Once the new lower point (M1) is determined, the calibration process can determine a new upper point (M2) for the calibration model. The upper model point (M2) follows directly from the new lower point (M1) and the constraint that the "Tc_leg1" point be on the line. The following equations can be used to acquire the new upper model point (M2) for the calibration model: <maths id="math0004"><math display="block"><mi>Tc</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo>⁢</mo><mi mathvariant="normal">b</mi><mo mathvariant="normal">=</mo><mfenced><mn mathvariant="normal">1</mn><mo mathvariant="normal">-</mo><mi mathvariant="normal">P</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo mathvariant="normal">/</mo><mi>P_leg</mi><mo>⁢</mo><mn mathvariant="normal">1</mn></mfenced><mo mathvariant="normal">*</mo><mi>Tc</mi><mo>⁢</mo><mn mathvariant="normal">1</mn><mo>⁢</mo><mi mathvariant="normal">b</mi><mo mathvariant="normal">+</mo><mi mathvariant="normal">P</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo mathvariant="normal">/</mo><mi>P_leg</mi><mo>⁢</mo><mn mathvariant="normal">1</mn><mo mathvariant="normal">*</mo><mi>Tc_leg</mi><mo>⁢</mo><mn mathvariant="normal">1</mn><mo mathvariant="normal">,</mo></math><img file="EP2575326A1_D0004.tif" /></maths> where P_leg1 is the pace corresponding to Tc_leg1. Hence, calibration following a second stage or leg serves to move both the lower model point (M1) and the upper model point (M2).

0066Another aspect of the invention pertains to a graphical user interface. The graphical user interface can be provided to assist a user in performing a calibration process (i.e., fine-tuning) the accuracy of the activity monitoring system. The graphical user interface can be provided on a display device of a portable electronic device that provides the activity monitoring system.

0067<figref idref="f0009 f0010 f0011 f0012 f0013">FIGs. 7-19</figref> are exemplary screens that pertain to fine-tuning accuracy of an activity monitoring system. In <figref idref="f0009">FIG. 7</figref>, a settings screen is illustrated with the "Shoes" item highlighted. Upon selection of the "Shoes" item, a shoes screen such as illustrated in <figref idref="f0009">FIG. 8</figref> can be displayed. As shown in <figref idref="f0009">FIG. 8</figref>, the "Fine-Tune" item is highlighted. When the "Fine-Tune" item is selected, a fine-tune status screen can be displayed such as illustrated in <figref idref="f0009">FIG. 9</figref>. In this example, the fine-tune status screen indicates that a walk-type fine-tune was performed on October 4, 2005 and that a run-type fine-tune was performed on October 8, 2005. The "Pro Run" item is shown in the fine-tune screen as not having yet been performed. When the "Run" item is selected from the fine-tune screen such as illustrated in <figref idref="f0009">FIG. 9</figref>, a fine-tune run screen such as illustrated in <figref idref="f0010">FIG. 10</figref> can be displayed. From the fine-tune run screen, a user can select either a 400 meter run or a custom distance to be utilized for a fine-tune operation. Alternatively, the user could reset the fine-tune run data to its default data. When the fine-tune run screen is used to select the "Custom Distance" item as shown in <figref idref="f0010">FIG. 11</figref>, a custom distance screen such as illustrated in <figref idref="f0010">FIG. 12</figref> can be displayed so that a user can enter a custom distance to be utilized with respect to the fine-tune run.

0068The fine-tune screen illustrated in <figref idref="f0011">FIG. 13</figref> shows the "Pro Run" item being highlighted. When the "Pro Run" item is selected, a fine-tune pro run screen such as illustrated in <figref idref="f0011">FIG. 14</figref> is displayed. The fine-tune pro run screen allows the user to elect to run at a slower pace or a faster pace for the fine-tune operation. Regardless of which pace is selected, a fine-tune pro run screen such as illustrated in <figref idref="f0011">FIG. 15</figref> is displayed. The fine-tune pro run screen illustrated in <figref idref="f0011">FIG. 15</figref> allows the user to select a predetermined distance, a custom distance or a reset operation.

0069Once the fine-tune run has been specified, the user can be presented with a music selection screen and then a start screen. Once the user has indicated that they have started the fine-tune run, a workout status screen can be displayed as discussed above. When a pause request has been activated, such as by pressing a predetermined button, a fine-tune pause screen such as illustrated in <figref idref="f0012">FIG. 16</figref> can be displayed. The fine-tune pause screen enables a user to end the fine-tuning or resume the fine-tuning. Regardless, when the fine-tune run has completed in a successful manner, a fine-tune run screen such as illustrated in <figref idref="f0012">FIG. 17</figref> can be displayed. Alternatively, when the fine-tune run does not complete successfully, error screens such as illustrated in <figref idref="f0013">FIG. 18 or FIG. 19</figref> can be displayed. The error screen shown in <figref idref="f0013">FIG. 18</figref> indicates that the distance run by the user was not the chosen distance for the fine-tuning. <figref idref="f0013">FIG. 19</figref> indicates that the user varied their pace too much during the fine-tuning run, which caused inaccuracies.

0070Although the calibration models illustrated in <figref idref="f0006">FIGs. 5</figref>, <figref idref="f0007">6A</figref> and <figref idref="f0008">6B</figref> utilize straight lines as calibration models, other calibration models could be utilized, such as calibration models that are curved or piecewise linear. In any case, in the event that a calibration model is unable to distinguish between multiple points, a stride time (Ts) can be utilized to discriminate between the multiple points on the calibration model. The stride time generally corresponds to the time period for a stride of a user (e.g., time period between successive heel contacts with the ground of a particular shoe).

0071Another aspect of the invention pertains to add to the storage of calibration data, such as a calibration model, at various locations within a system. For example, with respect to the sports monitoring system 100 illustrated in <figref idref="f0001">FIG. 1</figref>, the primary storage location for the calibration model is the portable media device 102. However, the calibration model can be stored at various other locations within the sports monitoring system 100. For example, the calibration model can be stored in the personal computer 110, the sports management server 118, the sports device 104, and/or the wireless interface accessory 106. There are different advantages for storing the calibration model at different parts of the sports monitoring system 100. Examples of the advantages for storing the calibration data at different parts of the sports monitoring system 100 are as follows. Since processing of activity data is normally performed at the portable media device 102, storage of the calibration model in the portable media device 102 allows for efficient processing. Storage of the calibration model in the wireless interface accessory 106 is useful because it renders the wireless interface accessory 106 portable with respect to different portable media devices. As an example, the wireless interface accessory 106 could be coupled to a different portable media device and operate properly without having to perform any recalibration operations. Similarly, storage of the calibration model in the sports device 104 should enable the sports device 104 to be fully portable between multiple different devices that might utilize the activity data captured by the sports device 104. Storage of the calibration model at the personal computer 110 can serve to provide backup storage for the calibration model as well as to permit processing of activity data at the personal computer. Storage of the calibration model at the sports management server 118 not only allows processing of activity data at the sports management server 118, but also facilitates gathering information on accurate calibration models for different groups of users. Advantageously, by having access to calibration models of numerous users, the sports monitoring system 100 could improve a default calibration model that is initially provided with the system. With a default calibration model that is sufficiently accurate, subsequent calibration by a user can be less necessary, simplified or eliminated.

0072According to another aspect of the invention, calibration models can be influenced by one or more other considerations. Examples of the other considerations are shoe type, gender, weight, fitness level, surface type, and inclination of surface. These other considerations can affect the calibration model, whether as a default or as a personalized calibration model.

0073In one embodiment, the system can detect the type of shoe being utilized by the user. The type of shoe can affect the calibration model, such as depending upon the stiffness of the shoe soles. Other characteristics of the shoe can also affect the calibration model. One approach to detecting the shoe stiffness is to include an electronic component within the shoe that can be sensed by another device, such as the portable media device or an accessory device. These sensors can, for example, include RFID tags, magnetic elements, or optical (e.g., infrared).

0074<figref idref="f0014">FIG. 20</figref> is an activity monitoring system 2000 for an electronic device according to another embodiment of the invention. The activity monitoring system 2000 is generally similar to the activity monitoring system 200 illustrated in <figref idref="f0002">FIG.2</figref> except that the activity application 202 further receives other sensor data 2002 in addition to the activity sensor data. The other sensor data 2002 can be used by the activity application 2002 when updating a calibration model 210. In one embodiment, the other sensor data 2002 provides data that pertains to shoe stiffness or other shoe characteristics (e.g., male or female type shoe). It should be noted that updating includes selection of an appropriate one of a plurality of calibration models, such as when a plurality of calibration models for different shoes are provided.

0075Another approach to determining shoe stiffness would be for the user to perform a predetermined action while wearing the shoe with the sports device 104. One type of predetermined action could pertain to the user jumping up and down. Besides these automatic approaches to determining shoe stiffness, in another embodiment, a user can manually interact with a user interface (e.g., such as a graphical user interface presented on a display of the user interface 204). As an example, the user interface can facilitate a user entering an indication of the type of shoe or its stiffness. As particular examples, a user could enter (i) a shoe model name or number, or (ii) a stiffness code provided on the shoe. As still another particular example, the user could navigate though a series of displayable images so as to select the shoe they are using by visual means.

0076In one embodiment, the system can detect the surface the user is running or walking on. For example, a sensor in the shoe, such as the sports sensor 104 or other sensor, could capture data that can signal the type of surface on which the user is running. For example, analysis of the captured data can be used to determine whether the user is running/walking indoors on a treadmill or running outdoors. As another example, analysis of the captured data can be used to determine whether the user is running/walking on hard surfaces (such as paved roads) or less hard surfaces (such as grass or athletic tracks). The captured data can thus be used to modify or select the calibration model for the type of surface.

0077Additionally, according to another aspect of the invention, a calibration model can be customized in view of calibration information available from a remote source. For example, the calibration model utilized by the portable media device 102 can be customized using calibration information or parameters available from the sports management server 118. For example, if the user of the portable media device 102 is also a user of the sports management server 118, the sports management server 118 may know certain characteristics, traits or other information about the user. For example, a user may have previously informed the sports management server 118 of one or more of shoe type, gender, weight, and fitness level. To the extent such information is useful to customize or improve a calibration model for the user, such information can be provided to the personal computer 110 and/or the portable media device 102 and utilized to provide an improved calibration model.

0078Another aspect of the invention pertains to performing calibration in a staged or deferred manner. With staged calibration, the calibration can be performed in parts. For example, a user may perform a walk calibration, which can lead to improvements to a default calibration model. Then, sometime later, the user can perform a run calibration at a slow pace that leads to further improvements to the calibration model. Still later, the user can perform a run calibration at a fast pace that can lead to still further improvements to the calibration model. Hence, as each stage of calibration is performed, the calibration model can be improved. However, none of the stages need be performed in any particular time or any particular order. Hence, the user is able to improve calibration as they have the time and interest to spend on calibration activities.

0079With deferred calibration, it is possible that the activity data that is transmitted by the sports device 104 to the wireless interface accessory 106 can be retained at any of a variety of different devices within the sports monitoring system 100. For example, the activity data could be stored at the personal computer 110 or the sports management server 118. By storing the activity data prior to its being processed with respect to a calibration model, such processing with respect to a calibration model can be performed sometime later when better and more accurate calibration models exist. This allows the devices of the sports monitoring system 100 to later reprocess activity data using improved calibration models. In other words, it allows after-the-fact processing of previously acquired activity data. This also allows analysis of a wide range of activity data across one or more calibration models.

0080Still another aspect of the invention pertains to merging different calibration models for the same user (e.g., same sports sensor 104). As noted above, calibration models can be stored at various locations within a system. These calibration models, if different, can be merged. For example, if a first calibration model resulted from a more recent slow run calibration and a second calibration model resulted from a more recent fast run calibration, then the first and second calibration models can be merged for improved accuracy. The merging of the calibration models can be performed from the calibration models themselves and/or the calibration data that yielded such calibration models.

0081During a calibration process, the user typically runs or walks a predetermined distance. It is important that the user's pace during the walk or run remain somewhat consistent. Hence, another aspect of the invention is for a portable media device to monitor the user's pace during the calibration walk or run. To the extent the user is not walking or running at a substantially consistent pace, the portable media device can alert the user through audio and/or visual feedback that they need to increase or decrease their pace to maintain the substantially consistent pace that is sought for the calibration process. Also, if during or at the conclusion of the calibration process the system recognizes that the pace of the calibration walk or run was not substantially consistent, the user can be notified that the calibration process was defective. Normally, the calibration data acquired during a defective calibration walk or run would be discarded.

0082The various aspects, embodiments, implementations or features of the invention can be used separately or in any combination.

0083The invention is preferably implemented by software, hardware or a combination of hardware and software. The invention can also be embodied as computer readable code on a computer readable medium. The computer readable medium is any data storage device that can store data which can thereafter be read by a computer system. Examples of the computer readable medium include read only memory, random-access memory, CD-ROMs, DVDs, magnetic tape, optical data storage devices, and carrier waves. The computer readable medium can also be distributed over network-coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

0084The many features and advantages of the present invention are apparent from the written description. Further, since numerous modifications and changes will readily occur to those skilled in the art, the invention should not be limited to the exact construction and operation as illustrated and described. Hence, all suitable modifications and equivalents may be resorted to as falling within the scope of the invention.

0085Before going on to set out the claims, we shall first provide a set of clauses describing embodiments of the invention: <ol id="ol0001"><li><i>1. A method for calibrating an activity monitoring system associated with a user, said method comprising:</i><ol id="ol0002" compact="compact"><li><i>(a) providing the activity monitoring system with a default calibration model;</i></li><li><i>(b) performing a first calibration to produce a first modified calibration model, the first modified calibration model being derived from the default calibration model; and</i></li><li><i>(c) subsequently performing a second calibration to produce a second modified calibration model, the second modified calibration model being derived from the first modified calibration model.</i></li></ol></li><li><i>2. A method as recited in clause 1, wherein the activity monitoring system monitors running or walking performed by a user.</i></li><li><i>3. A method as recited in clause 1, wherein the activity monitoring system is internal to a portable electronic device, such as a portable media player.</i></li><li><i>4. A method as recited in clause 1, wherein the first calibration is with respect to the user performing an activity that is monitored by the activity monitoring system at a first pace, and wherein the second calibration is with respect to the user performing an activity that is monitored by the activity monitoring system at a second pace.</i></li><li><i>5. A method as recited in clause 4, wherein the activity is running or walking by the user, and wherein the second pace is faster than the first pace.</i></li><li><i>6. A method as recited in clause 4, wherein the second pace pertains to a fast run, and wherein the first pace pertains to a slow run.</i></li><li><i>7. A method as recited in clause 4, wherein the second pace pertains to a fast walk, and wherein the first pace pertains to a slow walk.</i></li><li><i>8. A method as recited in clause 1, wherein the second modified calibration model is stored in multiple locations.</i></li><li><i>9. A method as recited in clause 1 , wherein the activity monitoring system includes at least a wearable portable electronic device that can operatively connect to a computer, and wherein the second modified calibration model is stored in both the wearable portable electronic device and the computer.</i></li><li><i>10. A method as recited in clause 1 , wherein the activity monitoring system includes an activity sensor and a wearable portable electronic device, and wherein the second modified calibration model is stored in both the wearable portable electronic device and the activity sensor.</i></li><li><i>11. A method as claimed in clause 1, wherein the first calibration is performed by a process comprising:</i><ol id="ol0003" compact="compact"><li><i>(a) receiving a calibration request from the user;</i></li><li><i>(b) receiving an indication of a calibration distance;</i></li><li><i>(c) awaiting a calibration start indication before starting activity to be used for calibration;</i></li><li><i>(d) receiving activity data from an activity sensor associated with the activity monitoring system during the activity used for calibration;</i></li><li><i>(e) estimating pace and</i>/<i>or distance based on the received activity data and an existing calibration model;</i></li><li><i>(f) awaiting receipt of a calibration stop indication;</i></li><li><i>(g) repeating said receiving (d) and said estimating (e) until said awaiting (f) receives the calibration stop indication; and</i></li><li><i>(h) modifying the existing calibration model based on at least the estimated distance from said estimating (e) and the calibration distance.</i></li></ol></li><li><i>12. A method as recited in clause 11, wherein said modifying (h) comprises:</i><ul id="ul0001" list-style="none" compact="compact"><li><i>(hi) determining an accuracy ratio based on the calibration distance and the estimated distance; and</i></li><li><i>(h2) modifying the existing calibration model based on the accuracy ratio.</i></li></ul></li><li><i>13. A method as recited in clause 12, wherein the existing calibration model is a line defined by a first point and a second point, wherein the line relates pace to ground contact time of a shoe of a user.</i></li><li><i>14. A method as recited in clause 13, wherein said modifying (h2) moves one of the first point and the second point an amount determined based on the accuracy ratio.</i></li><li><i>15. A method as recited in clause 13, wherein said modifying (h2) alters the line by pivoting the second point about the first point.</i></li><li><i>16. A method as recited in clause 13, wherein said modifying (h.2) alters the line by moving the first point and the second point.</i></li><li><i>17. A method as recited in clause 11, wherein said receiving (d) periodically receives the activity data.</i></li><li><i>18. A method for operating an activity monitoring system associated with a user utilizing at least one shoe, said method comprising:</i><ul id="ul0002" list-style="none" compact="compact"><li><i>calibrating an activity monitoring system using the method of any of clauses 1 to 17;</i><ul id="ul0003" list-style="none" compact="compact"><li><i>receiving shoe characteristic information pertaining to the shoe; and</i></li><li><i>operating the activity monitoring system based at least in part on the shoe characteristic information.</i></li></ul></li></ul></li><li><i>19. A method as recited in clause 18, wherein said operating comprises: modifying calibration data for use by the activity monitoring apparatus based at least in part on the shoe characteristic information.</i></li><li><i>20. A method as recited in clause 19, wherein said receiving receives the shoe characteristic information by user input with respect to a user input device of the activity monitoring system.</i></li><li><i>21. A method as recited in clause 20, wherein the shoe characteristic information is provided by the user input of a shoe type or code.</i></li><li><i>22. A method as recited in clause 19, wherein said receiving receives the shoe characteristic information from an electronic device within the shoe.</i></li><li><i>23. A method as recited in clause 22, wherein the electronic device within the shoe is a wireless device that can transmit the shoe characteristic information to the activity monitoring system.</i></li><li><i>24. A method as recited in clause 23, wherein the electronic device is a RFID device.</i></li><li><i>25. A portable electronic device, comprising:</i><ul id="ul0004" list-style="none" compact="compact"><li><i>a user interface for providing user input to said portable electronic device and user output from said portable electronic device;</i></li><li><i>a calibration model;</i></li><li><i>an activity application that operates to monitor a physiological characteristic of a user of said portable electronic device, said activity application receives sensor data acquired from a remote sensor associated with the user, and said activity application processes the sensor data in view of said calibration model;</i></li><li><i>a calibration engine that operates to modify said calibration model in view of a calibration activity for which sensor data from the remote sensor is acquired and processed by said activity application or said calibration engine.</i></li></ul></li><li><i>26. A portable electronic device as recited in clause 25, wherein said calibration model is defined by a line defined by first and second points, and wherein said calibration model is modified by moving both the first and second points.</i></li><li><i>27. A portable electronic device as recited in clause 25, wherein in response to a first calibration activity, the first point is moved, and wherein in response to a second calibration activity, the second point is moved.</i></li><li><i>28. A portable electronic device as recited in clause 26, wherein in response to a first calibration activity, the first point is moved, and wherein in response to a second calibration activity, both the first point and the second point are moved.</i></li><li><i>29. A portable electronic device as recited in clause 25, wherein said calibration engine modifies said calibration model based on at least an estimated distance for the calibration activity and an actual calibration distance.</i></li><li><i>30. A portable electronic device as recited in clause 29, wherein the actual calibration distance is provided by said user interface.</i></li><li><i>31. A portable electronic device as recited in clause 29, wherein said calibration engine modifies said calibration model based on an accuracy ratio based on the calibration distance and the estimated distance.</i></li><li><i>32. A portable electronic device as recited in clause 25, wherein at least one of said activity application and said calibration engine operate to monitor user performance during a calibration activity.</i></li><li><i>33. A portable electronic device as recited in clause 32, wherein at least one of said activity application and said calibration engine further operate to provide feedback to the user during the calibration activity.</i></li><li><i>34. A portable electronic device as recited in clause 33, wherein the calibration activity is running or walking, and wherein the feedback advises the user about their pace.</i></li><li><i>35. A computer readable medium including at least computer program code for calibrating an activity monitoring system associated with a user, said computer readable medium comprising:</i><ul id="ul0005" list-style="none" compact="compact"><li><i>computer program code for performing a first calibration to produce first modified calibration model, the first modified calibration model being derived from an existing calibration model; and</i></li><li><i>computer program code for subsequently performing a second calibration to produce a second modified calibration model, the second modified calibration model being derived from the first modified calibration model.</i></li></ul></li><li><i>36. A computer readable medium as claimed in clause 35 and further comprising:</i><ul id="ul0006" list-style="none" compact="compact"><li><i>computer program code for receiving an indication of a calibration distance; computer program code for awaiting a start indication before starting activity to be used for calibration;</i></li><li><i>computer program code for receiving activity data from an activity sensor associated with the activity monitoring system during the activity to be used for calibration;</i></li><li><i>computer program code for estimating pace and</i>/<i>or distance based on the received activity data and an existing calibration model;</i></li><li><i>computer program code for awaiting receipt of a stop indication that indicates the end of the activity to be used for calibration; and</i></li><li><i>computer program code for modifying the existing calibration model based on at least the estimated distance and the calibration distance.</i></li></ul></li></ol>