Accelerometer data compression

• US 9,742,432 B2
• Filed: 12/31/2010
• Issued: 08/22/2017
• Est. Priority Date: 12/31/2010
• Status: Active Grant

• Current Assignee: Tomtom Global Content B.V (TomTom NV)
• Original Assignee: TomTom International BV (TomTom NV), Tomtom Polska Sp. Z O.O. (TomTom NV)
• Inventors: Kmiecik, Marcin Michal, Da Cruz Gonalves, Nelson Miguel, Lai, Ying-Lin
• Primary Examiner(s): Bui, Bryan
• Application Number:
  US13/977,880
• Publication Number:
  US 20140046990A1
• Time in Patent Office: 2,426 Days
• Field of Search: 702141
• CPC Class Codes: A61B 2503/10 Athletes
• CPC Class Codes: A61B 2560/0475 Special features of memory means, e.g. removable memory cards
• CPC Class Codes: A61B 2562/0219 Inertial sensors, e.g. accelerometers, gyroscopes, tilt switches
• CPC Class Codes: A61B 2562/227 Sensors with electrical connectors
• CPC Class Codes: A61B 5/1112 Global tracking of patients, e.g. by using GPS
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: A61B 5/7232 involving compression of the physiological signal, e.g. to extend the signal recording period
• CPC Class Codes: G01C 22/006 Pedometers
• CPC Class Codes: H03M 7/30 Compression speech analysis-synthesis for redundancy reduction G10L19/00; for image communication H04N; Expansion; Suppression of unnecessary data, e.g. redundancy reduction

Abstract

A method of compressing data output from one or more accelerometers configured to be transported, carried or worn by a user is provided. Acceleration values indicative of the movement of the user are measured at a first frequency and values representative of the measured acceleration values are generated at a second frequency, which is lower than the first frequency. The step of generating comprises: defining a plurality of time windows, each time window containing a plurality of measured acceleration values; and applying a transformation to the measured acceleration values within each time window to generate a plurality of transformed values. For each time window, storing at least one of said plurality of transformed values and/or one or more parameters associated therewith.

Claims

1. A method comprising the steps of:

receiving, by a processor, a location of a mobile device configured to be transported, carried or worn by a user determined at a plurality of times during a journey from a first location to a second location;

receiving, by the processor, acceleration values indicative of the movement of the user and/or device a plurality of times during the journey measured at a first frequency;

generating, by the processor, values representative of the measured acceleration values at a second frequency, which is lower than the first frequency, said step of generating comprising;

defining a plurality of time windows, each time window containing a plurality of measured acceleration values; and

applying a transformation to the measured acceleration values within each time window to generate a plurality of transformed values; and

,

selecting, for each time window, at least one of said plurality of transformed values and/or one or more parameters derived from the plurality of transformed values to be stored;

storing;

(i) the received locations and/or data derived therefrom; and

(ii) the selected data derived from the acceleration values; and

transmitting the stored data from the mobile device to a remote server for use in providing a representation of the journey.

2. The method as claimed in claim 1, wherein the acceleration values are measured using one or more accelerometers.

3. The method as claimed in claim 1, wherein the first frequency is between 1 Hz and 20 Hz.

4. The method as claimed in claim 1, wherein the acceleration values are stored in a data buffer.

5. The method as claimed in claim 1, further comprising determining an absolute acceleration value indicative of the movement of the user from the measured acceleration values.

6. The method as claimed in claim 1, wherein the plurality of time windows are defined such that a portion of one time window overlaps a portion of an adjacent time window.

7. The method as claimed in claim 1, wherein the second frequency is between 0.1 and 2 Hz.

8. The method as claimed in claim 1, wherein transformation applied to the measured acceleration values comprises a fast Fourier transformation.

9. The method as claimed in claim 1, further comprising:

applying a transformation to the acceleration values within each time window to generate a frequency spectrum; and

storing one or more parameters associated with the frequency spectrum.

10. The method as claimed in claim 9, wherein the one or more parameters associated with the frequency spectrum comprise at least one of:

one or more indexed coefficients; and

one or more parameters derived from the indexed coefficients.

11. The method as claimed in claim 10, wherein said one or more parameters are selected from the group consisting of:

(i) the zero index amplitude;

(ii) the largest nonzero index amplitude;

(iii) the index associated with the largest amplitude; and

(iv) the sum of all the non-zero index amplitudes.

12. A mobile device configured to be transported, carried or worn by a user, comprising:

a receiver for determining the location of the mobile device at a plurality of times during a journey from a first location to a second location;

one or more accelerometers for measuring acceleration values indicative of the movement of the user and/or device at a plurality of times during the journey at a first frequency;

at least one processor arranged to generate values representative of the measured acceleration values at a second frequency, which is lower than the first frequency, by;

defining a plurality of time windows, each time window containing a plurality of measured acceleration values; and

applying a transformation to the measured acceleration values within each time window to generate a plurality of transformed values; and

the at least one processor being further arranged to select for each time window, at least one of said plurality of transformed values and/or one or more parameters derived from the plurality of transformed values to be stored;

at least one data storage device for storing data received from and/or derived from the receiver and the selected data derived from the one or more accelerometers; and

a transmitter for transmitting the stored data from the mobile device to a remote server for use in providing a representation of the journey.

13. The mobile device as claimed in claim 12, wherein said one or more accelerometers comprise a three-axis accelerometer.

14. The mobile device as claimed in claim 12, wherein the receiver comprises a global navigation satellite system (GNSS) receiver for determining the location of the user.

15. The mobile device as claimed in claim 12, wherein the mobile device is a portable personal training device comprising a housing having a strap for securing the device to a user.

16. A non-transitory computer-readable medium storing a set of instructions which, when executed by at least one processor, causes the at least one processor to perform a method, the method executed by the set of instructions comprising:

receiving a location of a mobile device configured to be transported, carried or worn by a user determined at a plurality of times during a journey from a first location to a second location;

receiving acceleration values indicative of the movement of the user and/or device a plurality of times during the journey measured at a first frequency;

generating values representative of the measured acceleration values at a second frequency, which is lower than the first frequency, said step of generating comprising;

defining a plurality of time windows, each time window containing a plurality of measured acceleration values; and

applying a transformation to the measured acceleration values within each time window to generate a plurality of transformed values; and

,

selecting, for each time window, at least one of said plurality of transformed values and/or one or more parameters derived from the plurality of transformed values to be stored;

storing;

(i) the received locations and/or data derived therefrom; and

(ii) the selected data derived from the acceleration values; and

transmitting the stored data from the mobile device to a remote server for use in providing a representation of the journey.

17. The computer-readable medium as claimed in claim 16, further comprising determining an absolute acceleration value indicative of the movement of the user from the measured acceleration values.

18. The computer-readable medium as claimed in claim 16, further comprising:

applying a transformation to the acceleration values within each time window to generate a frequency spectrum; and

storing one or more parameters associated with the frequency spectrum.

19. The computer-readable medium of claim 18, wherein the one or more parameters associated with the frequency spectrum comprise at least one of:

one or more indexed coefficients; and

one or more parameters derived from the indexed coefficients.

20. The computer-readable medium of claim 19, wherein said one or more parameters are selected from the group consisting of:

(i) the zero index amplitude;

(ii) the largest nonzero index amplitude;

(iii) the index associated with the largest amplitude; and

(iv) the sum of all the non-zero index amplitudes.