CODEWITHSUNDEEP
ioscore-motioncompass-geolocation
Damian Dudycz
Damian Dudycz

Reputation: 2800

CoreMotion based compass

I would like to calculate compass heading to true north using CoreMotion (Not CoreLocation if possible). I have found some formulas, but working only when phone is flat on the table. Can someone help me find a way to calculate compass heading, which will work in every device position like compass app?

Upvotes: 2

Views: 735

Answers (1)

Damian Dudycz
Damian Dudycz

Reputation: 2800

I have found an answer. This is how I get compass heading in radians from CoreMotion:

guard let a = motionManager.deviceMotion?.attitude, g = motionManager.deviceMotion?.gravity else { return }

let deviceAngle = { () -> Double in
    switch interfaceOrientation {
    case .LandscapeLeft:  return -M_PI_2 + atan2(g.x, g.y)
    case .LandscapeRight: return  M_PI_2 + atan2(g.x, g.y)
    default:              return  M_PI   + atan2(g.x, g.y)
    }
}()

// Calculate Heading.
let cA = cos(a.yaw), sA = sin(a.yaw), sB = sin(a.pitch), cG = cos(a.roll), sG = sin(a.roll)
let rA = cA * sG + sA * sB * cG
let rB = sA * sG - cA * sB * cG
var compassHeading = -atan(rA / rB) + M_PI + deviceAngle
if rB > 0 { compassHeading += M_PI }

Still need to test this, but for now it seems to work.

Upvotes: 2

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