如何告诉用户准确的度数是朝北还是朝东？答案

【问题标题】：How to tell user accurate degrees to face north or east?如何告诉用户准确的度数是朝北还是朝东？
【发布时间】：2019-08-09 16:49:00
【问题描述】：

我正在创建一个导航应用程序。我想知道我当前的航向和东方之间的度数。我这样做的方式是用角度 0 减去真实航向，如果是北，则为 90 度，以此类推。当差异达到let i: ClosedRange<Double> = 0...20 时，我猜测航向朝向预期的方向，在本例中为东方。

我想知道这是否是完美的方法。如果我应该使用轴承，我仍然感到困惑。

  //calculate the difference between two angles ( current heading and east angle, 90 degrees)

    func cal(firstAngle: Double) -> Double {
        var diff = heading - 90
        if diff < -360 {
            diff += 360
        } else if diff > 360 {
            diff -= 360
        }
        return diff
    }

// check if the difference falls in the range
let i: ClosedRange<Double> = 0...20

if !(i.contains(k)) {
    k = cal(firstAngle: b)
    } else if (i.contains(k)) {
    let message = "You are heading east"
     print(message)
      } else {return}
   }

  func locationManager(_ manager: CLLocationManager, didUpdateHeading newHeading: CLHeading) {
        var heading = newHeading.trueHeading }

【问题讨论】：

标签： swift navigation maps

【解决方案1】：

这应该可以满足您的需求。代码中的注释：

func cal(heading: Double, desired: Double) -> Double {
    // compute adjustment
    var angle = desired - heading

    // put angle into -360 ... 360 range
    angle = angle.truncatingRemainder(dividingBy: 360)

    // put angle into -180 ... 180 range
    if angle < -180 {
        angle += 360
    } else if angle > 180 {
        angle -= 360
    }

    return angle
}

// some example calls
cal(heading: 90, desired: 180)  // 90
cal(heading: 180, desired: 90)  // -90
cal(heading: 350, desired: 90)  // 100
cal(heading: 30, desired: 270)  // -120 

let within20degrees: ClosedRange<Double> = -20...20

let adjust = cal(heading: 105, desired: 90)
if within20degrees ~= adjust {
    print("heading in the right direction")
}

heading in the right direction

【讨论】：

谢谢，先生！这就是我一直在努力的。