An equipment fitting system that measures swings by a user of different pieces of equipment with inertial sensors, and analyzes sensor data to recommend which piece of equipment is optimal for the user from among those tested. Illustrative applications include fitting of baseball bats and golf clubs. Swing metrics calculated from sensor data may include an acceleration metric, a speed metric, and a momentum metric; these metrics may be combined into a metrics score for each piece of equipment. Other factors may be included in an overall score, such as the user's subjective score for each piece of equipment, and ratings from experts or other consumers. Users may assign the relative importance for the different factors to calculate an overall equipment score.

Examples of the disclosure describe systems and methods for presenting virtual content on a wearable head device. In some embodiments, a state of a wearable head device is determined by minimizing a total error based on a reduced weight associated with a reprojection error. A view reflecting the determined state of the wearable head device is presented via a display of the wearable head device. In some embodiments, a wearable head device calculates a first preintegration term and second preintegration term based on the image data received via a sensor of the wearable head device and the inertial data received via a first IMU and a second IMU of the wearable head device. The wearable head device estimates a position of the device based on the first and second preintegration terms, and the wearable head device presents the virtual content based on the position of the device.

Examples of the disclosure describe systems and methods for presenting virtual content on a wearable head device. In some embodiments, a state of a wearable head device is determined by minimizing a total error based on a reduced weight associated with a reprojection error. A view reflecting the determined state of the wearable head device is presented via a display of the wearable head device. In some embodiments, a wearable head device calculates a first preintegration term and second preintegration term based on the image data received via a sensor of the wearable head device and the inertial data received via a first IMU and a second IMU of the wearable head device. The wearable head device estimates a position of the device based on the first and second preintegration terms, and the wearable head device presents the virtual content based on the position of the device.

Techniques and methodologies for servicing a shock strut are provided that account for the variability in gas solubility of the shock strut while in-service. These examples incorporates knowledge of the shock strut's stoke history in order to estimate/predict the amount of gas in solution, its percentage saturation, etc. This may permit a more refined knowledge of the true servicing state of the shock strut.

Techniques and methodologies for servicing a shock strut are provided that account for the variability in gas solubility of the shock strut while in-service. These examples incorporates knowledge of the shock strut's stoke history in order to estimate/predict the amount of gas in solution, its percentage saturation, etc. This may permit a more refined knowledge of the true servicing state of the shock strut.

A travelling direction calculation apparatus includes an acceleration sensor, a period identification unit, an action determination unit, a vector calculator, and a travelling direction decision unit. The period identification unit identifies a stable measurement period and an idling leg period based on change in a vertical component of acceleration detected by the acceleration sensor. The action determination unit discriminates between walking and running by using the minimum value of the vertical component of the acceleration in the idling leg period. The vector calculator calculates a velocity vector from a horizontal component of the acceleration in the stable measurement period. The travelling direction decision unit decides a direction of traveling of a user based on a result of determination performed by the action determination unit and the velocity vector calculated by the vector calculator.

An equipment fitting system that measures swings by a user of different pieces of equipment with inertial sensors, and analyzes sensor data to recommend which piece of equipment is optimal for the user from among those tested. Illustrative applications include fitting of baseball bats and golf clubs. Swing metrics calculated from sensor data may include an acceleration metric, a speed metric, and a momentum metric; these metrics may be combined into a metrics score for each piece of equipment. Other factors may be included in an overall score, such as the user's subjective score for each piece of equipment, and ratings from experts or other consumers. Users may assign the relative importance for the different factors to calculate an overall equipment score.

A system and method wherein ball spin rate and axis orientation are determined according to an electronic circuit that includes a magnetometer spin sensor module and, in the alternative, an electronic circuit that includes a spin sensor module with a plurality of accelerometers.

A measuring device includes a measured value obtainer, a display device configured to display a measured value obtained by the measured value obtainer, an illumination device configured to emit a light to the display device, a measurement state obtainer configured to obtain information regarding a state in which a measured value is obtained by the measured value obtainer, and an illumination color changer configured to change a color of the light in accordance with a measurement state obtained by the measurement state obtainer.

A measuring device includes a measured value obtainer, a display device configured to display a measured value obtained by the measured value obtainer, an illumination device configured to emit a light to the display device, a measurement state obtainer configured to obtain information regarding a state in which a measured value is obtained by the measured value obtainer, and an illumination color changer configured to change a color of the light in accordance with a measurement state obtained by the measurement state obtainer.