Performance; Calibration Basics - Nokia NPL-4 Series Manual

NPL-4/5/RM-104
System Module and User Interface

Performance

Calibration basics

Calibration process target is to normalize measured x and y value before calculation to
heading angle, exactly: calibration removes harmful effects of phone own
Calibration is needed because every phone has different magnetic behaviour and also the
geographical places are different
Recalibration is needed because phone has drift on magnetization level depending user
actions and geographical place changes
Basically in phone levels are two type of normalization,
• offset drift
• ellipse correction
User action: rotate phone
• one to two round needed (360 to 720 degree)
Phone actions
• Measures x and y values during rotating
• Judges calibration success
• Calculates calibration output values
Calibration outputs (parameter values)
• offset drift values: xmin, xmax, ymin, ymax
² 1 ellipse correction: scorra and scorrb
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