Systems and methods are disclosed for categorizing a device use case for on foot motion with a portable device. Motion sensor data corresponding to motion of the portable device may be obtained, such as from a sensor assembly of the device. The motions sensor data is processed. Further, a use case characteristic may be determined from the processed and/or raw motion sensor data, an effective frequency may be determined from the processed and/or raw motion sensor data and/or an Eigen use case may be determined. The device use case may then be classified using the processed and/or raw motion sensor data and at least one of the use case characteristic, the effective frequency and the Eigen use case.
Please help me write a proper abstract based on the patent claims. CLAIM: 1. A method for categorizing a device use case for on foot motion with a portable device comprising: (a) obtaining motion sensor data corresponding to motion of the portable device; (b) performing at least one of: (i) deriving a use case characteristic from the motion sensor data; (ii) determining an effective frequency from the motion sensor data; and (iii) determining an Eigen use case; and (c) categorizing the device use case of the portable device using the motion sensor data and at least one of the use case characteristic, the effective frequency and the Eigen use case. 2. The method of claim 1, further comprising processing the motion sensor data. 3. The method of claim 2, wherein processing the motion sensor data comprises transforming the motion sensor data at least in part with a determined orientation of the portable device. 4. The method of claim 3, wherein processing the motion sensor data characterizes vertical acceleration by leveling accelerometer data using the determined orientation of the portable device. 5. The method of claim 4, wherein processing the motion sensor data to characterize vertical acceleration further comprises subtracting gravity. 6. The method of claim 3, wherein processing the motion sensor data characterizes horizontal motion by leveling accelerometer data using the determined orientation of the portable device. 7. The method of claim 2, wherein processing the motion sensor data further comprises determining magnitude for gyroscope data. 8. The method of claim 1, wherein deriving the at least one use case characteristic comprises performing a statistical analysis. 9. The method of claim 1, wherein deriving the at least one use case characteristic comprises determining an effective orientation component. 10. The method of claim 9, further comprising detecting peaks in the effective orientation component. 11. The method of claim 10, wherein detecting peaks comprises applying a threshold determined at least in part on a statistical analysis of the effective orientation component. 12. The method of claim 1, wherein deriving the at least one use case characteristic comprises determining a radius of rotation value for the portable device. 13. The method of claim 1, wherein deriving the at least one use case characteristic comprises detecting peaks in the motion sensor data. 14. The method of claim 13, wherein detecting peaks comprises applying a threshold determined at least in part on a statistical analysis of the motion sensor data. 15. The method of claim 13, wherein detecting peaks comprises determining peaks frequency. 16. The method of claim 13, wherein detecting peaks further comprises determining a range of the peaks frequency. 17. The method of claim 16, wherein detecting peaks further comprises determining a threshold for the range of the peaks frequency. 18. The method of claim 1, wherein deriving the at least one use case characteristic comprises assigning an attribute to the motion sensor data. 19. The method of claim 18, wherein assigning the at least one attribute of the motion sensor data is based at least in part on a derived use case characteristic. 20. The method of claim 18, wherein assigning the at least one attribute of the motion sensor data comprises assigning a not dangling attribute. 21. The method of claim 18, wherein assigning the at least one attribute of the motion sensor data comprises assigning a dangling attribute. 22. The method of claim 18, wherein assigning the at least one attribute of the motion sensor data comprises assigning a pocket attribute. 23. The method of claim 18, wherein assigning the at least one attribute of the motion sensor data comprises assigning a radius of rotation attribute. 24. The method of claim 18, wherein assigning the at least one attribute of the motion sensor data comprises assigning a slow radius of rotation attribute. 25. The method of claim 18, wherein assigning the at least one attribute of the motion sensor data comprises assigning a general attribute. 26. The method of claim 18, wherein assigning the at least one attribute of the motion sensor data comprises assigning a belt attribute. 27. The method of claim 18, wherein assigning the at least one attribute of the motion sensor data comprises assigning an on ear attribute. 28. The method of claim 1, further comprising identifying unstable motion characteristics. 29. The method of claim 28, wherein categorizing the device use case of the portable device is based at least in part on assigning at least one attribute of the motion sensor data. 30. The method of claim 1, further comprising identifying normal motion characteristics. 31. The method of claim 30, wherein categorizing the device use case of the portable device is based on at least one or a combination of the following: (i) a statistical analysis of the motion sensor data; (ii) a statistical analysis of an effective orientation component; (iii) a radius of rotation value; (iv) identifying a number of peaks in the motion sensor data and comparing it to a threshold; and (v) a range of peaks in the motion sensor data. 32. The method of claim 30, wherein categorizing the device use case of the portable device is based at least in part on detecting a characteristic pattern of peaks in the motion sensor data. 33. The method of claim 32, wherein categorizing the device use case of the portable device is further based on a range of peaks in the motion sensor data. 34. The method of claim 30, wherein categorizing the device use case of the portable device is based at least in part on assigning at least one attribute of the motion sensor data. 35. The method of claim 1, wherein categorizing the device use case of the portable device is based on an effective frequency in the motion sensor data. 36. The method of claim 35, wherein the effective frequency is determined using a frequency domain analysis. 37. The method of claim 36, wherein the frequency domain analysis includes a Fast Fourier Transformation (FFT). 38. The method of claim 35, wherein the effective frequency is determined using a time domain analysis. 39. The method of claim 35, wherein the effective frequency is determined using a time domain analysis and by calculating a signal power and a power ratio of the motion sensor data. 40. The method of claim 1, wherein categorizing the device use case of the portable device is further based on determination of an Eigen use case. 41. The method of claim 40, further comprising matching features extracted from the motion sensor data to at least one stored Eigen use case to determine the device use case. 42. The method of claim 41, wherein the at least one stored Eigen use case comprises a set of eigenvectors developed during a training phase. 43. The method of claim 1, further comprising deriving a navigation solution for the portable device based at least in part on the motion sensor data and the categorization of device use case. 44. A portable device for categorizing a device use case for the portable device comprising: a sensor assembly integrated with the portable device, configured to output data representing motion of the portable device; a categorizer configured to perform at least one of the operations of: deriving a use case characteristic from the motion sensor data; determining an effective frequency from the motion sensor data; and determining an Eigen use case; wherein the categorizer determines a device use case for the portable device using the motion sensor data and at least one of the use case characteristic, the effective frequency and the Eigen use case; and a processor configured to run the categorizer. 45. The portable device of claim 44, wherein the processor is further configured to process the motion sensor data. 46. The portable device of claim 44, further comprising a navigation module configured to provide a navigation solution for the portable device derived at least in part on the motion sensor data and the determined device use case. 47. The portable device of claim 44, wherein the sensor assembly includes an accelerometer and a gyroscope. 48. The device of claim 44, wherein the sensor assembly comprises an inertial sensor implemented as a Micro Electro Mechanical System (MEMS).