The Journal of the Institute of Internet, Broadcasting and Communication (한국인터넷방송통신학회논문지)

The Institute of Internet, Broadcasting and Communication (한국인터넷방송통신학회)
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A Study on magnetic sensor calibration for indoor smartphone position tracking

스마트폰 실내 위치 추적을 위한 지자기 센서 보정에 관한 연구

  • 이동욱 (한성대학교 전자정보공학과) ;
  • 오종택 (한성대학교 전자정보공학과)
  • Received : 2018.10.08
  • Accepted : 2018.12.07
  • Published : 2018.12.31
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Abstract

Research on indoor location tracking technology using smart phone is actively being carried out. Especially, in order to display the movement path of the smartphone on the map, the azimuth angle should be estimated by using the geomagnetic sensor built in most smart phones. Due to the distortion of the magnetic field due to the surrounding steel structure and the inclination of the smartphone, the estimation error of azimuthal angle may be occurred. In this paper, we propose a correction method of the geomagnetic sensor at the stationary state and a correction method for the inclination of the smartphone. We also propose a method to correct the azimuth error due to the difference between the magnetic north and the grid north.

스마트폰을 이용한 실내 위치 추적 기술에 관한 연구가 활발하게 진행되고 있다. 특히 스마트폰의 이동 경로를 지도에 표시하기 위해서는 대부분의 스마트폰에 내장되어 있는 지자기 센서를 이용하여 방위각을 추정해야 하는데, 주변의 쇠구조물에 의한 자기장의 왜곡과 스마트폰의 기울어짐 때문에 방위각 추정 오차가 발생한다. 본 논문에서는 정지 상태에서의 지자기 센서의 보정 방법과 스마트폰의 기울어짐에 대한 보정 방법을 제시한다. 또한 스마트폰에서 자북과 도북의 차이에 의한 방위각 오차를 보정하는 방법을 제안한다.

Keywords

OTNBBE_2018_v18n6_229_f0001.png 이미지

그림 3. 자북과 도북의 차이 Fig. 3. The difference between magnetic north and grid north

OTNBBE_2018_v18n6_229_f0002.png 이미지

그림 4. soft iron 왜곡 Fig. 4. soft iron distortion

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그림 1. (a) 자기장의 세기가 35~40μT 인 장소(실선)와 범위 밖인 장소(점선)에서 제자리에서 한 바퀴 회전하면서 지자기 센서로 측정한 방위각의 궤적과 중심점 (b) 범위 밖인 장소에서 실제 방위각과 지자기 센서 값으로 측정된 방위각의 오차 Fig. 1. (a) Locus and center of azimuth angle measured by geometric sensor, when rotating one turn in the place of the magnetic field strength of 35 ~ 40μT (solid line) and of outside the range (dotted line). (b) Azimuthal measurement error between the actual azimuth and the angles with geomagnetic sensor at a location outside the range.

OTNBBE_2018_v18n6_229_f0004.png 이미지

그림 2. (a) 스마트폰이 수평상태(실선) 및 pitch(점선), roll(1점쇄선)각이 각각 45도일 때의 지자기 센서 값에 의한 측정 방위각 궤적 그래프, (b) 이때의 측정 방위각 측정 오차 Fig. 2. (a) A graph of azimuthal trajectory measured by the geomagnetic sensor value when the smartphone is horizontal(solid line) and the pitch(dotted line) and roll(1 dot chain line) angles are 45 degrees, each. (b) The azimuth measurement error.

OTNBBE_2018_v18n6_229_f0005.png 이미지

그림 5. (a) 수평자기벡터 왜곡 보정, (b) 센서 데이터 왜곡 보정, (c) 수평자기벡터 왜곡 보정 전/후의 방위각 비교, (d) 센서 데이터 왜곡 보정 전/후의 방위각 비교. Fig. 5. (a) Horizontal magnetic vector distortion correction, (b) Sensor data distortion correction, (c) Comparison of azimuth angle before and after horizontal magnetic vector distortion correction, (d) Comparison of azimuth angle before and after sensor data distortion correction.

표 1. 식 (3), (4)에서 사용된 변수들 Table 1. Variables used in equations (3) and (4)

OTNBBE_2018_v18n6_229_t0001.png 이미지

표 2. 각각의 실험에 대한 조건들 Table 2. Conditions for each experiment

OTNBBE_2018_v18n6_229_t0002.png 이미지

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