Wearable Stride Length Calibration via Step Rate and GPS Correlation
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Solution Overview
Problem
Existing wearable devices face challenges in accurately calculating stride length, pace, and speed without GPS data, particularly when GPS signals are unavailable or when users engage in activities with varying stride lengths at different paces or speeds.
Innovation Solution
The use of accelerometers in wearable devices to determine step rate, combined with user-specific information and activity-specific data, allows for the estimation and verification of stride length, pace, and speed, even without GPS, by correlating step rates with stored database records and updating them based on actual distance traveled during GPS-enabled activities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS tracking data is used to calculate stride length, then measurement precision is improved, but device complexity increases and reliability deteriorates when GPS signals are unavailable
Solution Approach 1:
The patent introduces an intermediary calibration process that uses GPS data when available to train a machine learning model, which then serves as a mediator to estimate stride length without GPS. The calibration phase captures the relationship between GPS-measured stride lengths and accelerometer-based step rates, creating a predictive model that can operate independently of GPS signals.
Solution Approach 2:
The system performs preliminary calibration during periods when GPS signals are available, storing calibrated stride length data in a database. This preliminary action prepares the system in advance for GPS-denied environments by pre-computing and storing the relationships between step rates and stride lengths under various conditions.
2Measurement precision
If GPS module is included in the wearable device, then stride length measurement precision is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent extracts the GPS functionality from the wearable device itself, placing it in an external portable device. The wearable device only needs to communicate step rate data to the portable device, which performs the complex GPS tracking and stride length calculation. This extraction reduces the complexity and power requirements of the wearable device while maintaining measurement precision.
3Device complexity
If stride length is calculated using only accelerometer data and user information, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The system performs preliminary calibration during periods when GPS signals are available, storing calibrated stride length data in a database. This preliminary action prepares the system in advance for GPS-denied environments by pre-computing and storing the relationships between step rates and stride lengths under various conditions.
Solution Approach 2:
The system uses feedback from GPS-tracked stride lengths to continuously refine and update the calibrated stride length database. When GPS data is available, the system compares calculated stride lengths with GPS-measured distances, using this feedback to improve the accuracy of future estimates in GPS-denied environments.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method provides accurate and reliable calculations of stride length, pace, and speed in GPS-denied environments, ensuring consistent and durable data for users during various activities, such as treadmill use or indoor workouts.
Implementation Method 1
These devices typically comprise an accelerometer, e.g., a three-axis accelerometer, and software for interpreting raw data gathered by the accelerometer
Data Source
AI summary
Described herein are systems, devices, and methods for determining a user's stride length and monitoring various aspects of the user's activities. An apparatus worn or carried by the user may determine and track when a user takes a step and, based at least in part on user-specific information, determine an estimated stride length of the user associated with a respective step rate or step rate range. The apparatus may further monitor the physical location, speed, or pace of the user during an activity and, in conjunction with step count information, determine a verified stride length for the user associated with a respective step rate or step rate range. The estimated and verified stride length determinations may be stored and used to determine one or more aspects of a user's subsequent activities, including but not limited to pace, speed, and calorie expenditure information, even when physical location information is unavailable.