Orientation Sensor Calibration Using Celestial Reference Points
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Solution Overview
Problem
Achieving high orientation accuracy with low-cost sensors in mobile devices is challenging, especially in environments with strong magnetic fields or ferrous materials, where existing calibration methods are inadequate.
Innovation Solution
The method involves recalibrating orientation sensors using celestial objects, which are identified through image capture and their known positions, allowing for accurate compass readings by determining angular measurements and applying corrections to sensor measurements based on almanac data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If low-cost orientation sensors are used in mobile devices, then device cost is reduced and portability is improved, but orientation measurement accuracy deteriorates
Solution Approach 1:
The patent introduces celestial objects (sun, moon, stars) as intermediary reference points for calibration. By capturing images of these known celestial positions and comparing them with sensor readings, the system establishes correction factors that mediate between low-cost sensor outputs and accurate orientation measurements, resolving the accuracy-cost contradiction
Solution Approach 2:
The patent changes the calibration parameters by using celestial body positions (azimuth and elevation angles) as reference standards. This parameter-based calibration approach allows the system to adjust and correct sensor measurements dynamically, improving orientation accuracy without requiring expensive hardware modifications
2Measurement precision
If traditional calibration methods are used in factory or by user, then initial sensor accuracy is improved, but accuracy deteriorates in environments with strong magnetic fields or ferrous materials
Solution Approach 1:
The patent extracts the orientation calibration process from magnet-dependent methods and relocates it to celestial object-based reference systems. By removing the dependency on magnetic fields and using astronomical references instead, the system eliminates the harmful effect of magnetic interference while maintaining calibration accuracy
Solution Approach 2:
The patent converts the limitation of low-cost sensors (susceptibility to magnetic interference) into an opportunity to adopt alternative calibration methods. By using celestial objects that are unaffected by terrestrial magnetic fields, the system transforms the harmful magnetic environment into a non-factor, enabling accurate orientation measurement even in magnetically challenging conditions
3Measurement precision
If continuous or occasional automatic calibration is performed during normal operation, then orientation accuracy is maintained, but device complexity and processing requirements increase
Solution Approach 1:
The patent implements self-service calibration by enabling the device to automatically capture images of celestial objects, identify their positions, compute calibration parameters, and update sensor corrections without user intervention. This self-calibrating mechanism maintains high orientation accuracy while managing system complexity through automated workflows that leverage existing device components
Data Source
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AI summary
A mobile device configured to be used in a wireless communication network includes: an image capture device; at least one sensor configured to measure a first orientation of the mobile device; and a processor communicatively coupled to the image capture device and the at least one sensor and configured to: identify an object in an image captured by the image capture device; use a position of the mobile device to determine an actual location of the object relative to the mobile device; and use the actual location of the object relative to the mobile device and the image to determine a correction for the sensor.