import { Injectable } from '@angular/core'; import { Observer, Observable } from 'rxjs'; @Injectable() export class DeviceOrientationService { compassHeading(alpha, beta, gamma):number { // Convert degrees to radians var alphaRad = alpha * (Math.PI / 180); var betaRad = beta * (Math.PI / 180); var gammaRad = gamma * (Math.PI / 180); // Calculate equation components var cA = Math.cos(alphaRad); var sA = Math.sin(alphaRad); var cB = Math.cos(betaRad); var sB = Math.sin(betaRad); var cG = Math.cos(gammaRad); var sG = Math.sin(gammaRad); // Calculate A, B, C rotation components var rA = - cA * sG - sA * sB * cG; var rB = - sA * sG + cA * sB * cG; var rC = - cB * cG; // Calculate compass heading var compassHeading = Math.atan(rA / rB); // Convert from half unit circle to whole unit circle if(rB < 0) { compassHeading += Math.PI; }else if(rA < 0) { compassHeading += 2 * Math.PI; } return compassHeading * (180/Math.PI); } getCurrentCompassHeading(): Observable { return Observable.create((observer: Observer) => { window.addEventListener("deviceorientation", (event:DeviceOrientationEvent)=>{ let heading = this.compassHeading(event.alpha,event.beta,event.gamma); if(!Number.isNaN(heading)) { observer.next(heading); } } ); }); } }