E-compass chip for precision dead-reckoning navigation

May 06, 2016 // By Graham Prophet
Indoor and undercover navigation using mobiles and wearables is the target for STMicroelectronics’ electronic compass IC; the eCompass, with magnetic-sensing technology, promises accuracy and superior temperature stability, enabling high-precision pedestrian dead reckoning, to enhance user experience of fitness tracking/mapping and indoor-navigation apps.

Integration of a high-performance MEMS accelerometer saves space and power compared to existing alternatives, ST adds. Fitness-tracking smartphone apps, smartwatches, and bands need continuous location data for mapping and recording, and accuracy is critical for wearers who like to monitor their progress and share achievements online. A built-in eCompass helps calculate location when satellite signals are unavailable, such as inside buildings or when running or cycling under tree cover. However, current solutions can give errors of about 10° in latitudes such as Northern Italy or Northern California. This can put the user off course by 150m or more in every km travelled.

ST’s LSM303AGR eCompass cuts the heading error to less than 4°, using the company’s technology for manufacturing high-accuracy magnetic sensors. This enhanced accuracy, combined with ultra-low-power operation consuming up to 50% less than competing devices when in low-power mode, is offered for high-precision Pedestrian Dead Reckoning (PDR) on mobile devices.

The LSM303AGR also enhances dead-reckoning accuracy in applications such as automotive navigation, and maintains accuracy over the full temperature range from -40°C to 85°C, whereas competing devices can vary by as much as 35% or more over small intervals such as between normal room temperature and human-body temperature.