ios - 位置变化时极地到笛卡尔的转换

Question

我已经搜索 SO 和 Unity Answers 数周了，但无法解决这个问题。我在 Unity 中有一个 3d 对象，它是根据用户当前的纬度/经度(比如 41.23423，-122.87978)实例化的，然后我想在对象的位置发生变化时将该对象移动到新的纬度/经度。

所以 41.23423, -122,87978 在我的 3D 环境中变为 0,0,0 并且我应用相对于原始位置的更改。

我在 C# 中编码，当位置更改触发 Action 时，我比较两个纬度/经度并计算距离和角度，然后进行极坐标到笛卡尔的转换并将对象移动到新位置。

我的问题是更新正在移动对象，但产生了一些不稳定的结果，我猜这是我的代码中的一个问题。例如，如果我在两个位置之间切换，第一个更改将移至 (131.6, 0.0, 0.0) 但随后将其切换回移动不会移动对象。或者我也曾在测试场合看到，第一次更改会产生意外坐标，但任何后续更改(在两点之间切换)都会为每个位置产生相同的相对值。

我不能很好地处理我在这里做错了什么，所以任何帮助将不胜感激，如果这个问题太模糊或重复的问题(我的代码中的问题或者可能我没有正确处理问题)

这是我的类的代码，它根据位置移动对象。

using UnityEngine;
using System.Collections;
using System;

public class CameraMover : MonoBehaviour {
const double PIx = 3.141592653589793;
const double RADIO = 20925721.8;
public CoreLocationData lastLocationData;
public int firstUpdate = 0;
private Vector3 currentVector;
private Vector3 newVector;
// Use this for initialization
void OnEnable () {
CoreLocationManager.locationServicesDidUpdate += locationServicesDidUpdate;

}

// Update is called once per frame
void Update () {

}

public void locationServicesDidUpdate( CoreLocationData locationData )
{
    if (firstUpdate == 0)
    lastLocationData = locationData;

    double newDistance = DistanceBetweenPlaces(lastLocationData.longitude, lastLocationData.latitude, locationData.longitude, locationData.latitude);
    double angleToMove = Angle(lastLocationData.latitude, lastLocationData.longitude, locationData.latitude, locationData.longitude);

    double newX = (newDistance * Math.Cos(angleToMove));
    double newZ = (newDistance * Math.Sin(angleToMove));
    float newXfloat = System.Convert.ToSingle(newX);
    float newZfloat = System.Convert.ToSingle(newZ);

    currentVector = this.gameObject.transform.position;
    newVector = new Vector3(newXfloat, 0.0F, newZfloat);
    this.gameObject.transform.position = Vector3.Lerp(currentVector, newVector, 1);

    Debug.Log(string.Format("Distance To Move is {0}, angle is {1}", newDistance, angleToMove));
    Debug.Log(string.Format("Moving from {0} to {1}", currentVector, newVector));
    lastLocationData = locationData;

    firstUpdate = 1;

}

public static double Radians(double x)
{
    return x * PIx / 180;
}

public static double DistanceBetweenPlaces(
    double lon1,
    double lat1,
    double lon2,
    double lat2)
{
    double dlon = Radians(lon2 - lon1);
    double dlat = Radians(lat2 - lat1);

    double a = (Math.Sin(dlat / 2) * Math.Sin(dlat / 2)) + Math.Cos(Radians(lat1)) * Math.Cos(Radians(lat2)) * (Math.Sin(dlon / 2) * Math.Sin(dlon / 2));
    double angle = 2 * Math.Atan2(Math.Sqrt(a), Math.Sqrt(1 - a));
    return angle * RADIO;
}


public double Angle(double px1, double py1, double px2, double py2)
{
// Negate X and Y values
double pxRes = px2 - px1;
double pyRes = py2 - py1;
double angle = 0.0;
// Calculate the angle
if (pxRes == 0.0)
{
   if (pxRes == 0.0)
         angle = 0.0;
   else if (pyRes > 0.0)          angle = System.Math.PI / 2.0;
   else
         angle = System.Math.PI * 3.0 / 2.0;
}
else if (pyRes == 0.0)
{
   if (pxRes > 0.0)
         angle = 0.0;
   else
         angle = System.Math.PI;
}
else
{
   if (pxRes < 0.0)
         angle = System.Math.Atan(pyRes / pxRes) + System.Math.PI;
   else if (pyRes < 0.0)          angle = System.Math.Atan(pyRes / pxRes) + (2 * System.Math.PI);
   else
         angle = System.Math.Atan(pyRes / pxRes);
}
// Convert to degrees
angle = angle * 180 / System.Math.PI;return angle;

}
}

编辑

正确实现:

using UnityEngine;
using System.Collections;
using System;

public class CameraMover : MonoBehaviour
{
  const double RATIO = 20902231.0029;
  public CoreLocationData lastLocationData;
  public int firstUpdate = 0;
  private Vector3 currentVector;
  private Vector3 newVector;

  // Use this for initialization
  void OnEnable ()
  {
    CoreLocationManager.locationServicesDidUpdate += locationServicesDidUpdate;
  }

  // Update is called once per frame
  void Update () { }

  public void locationServicesDidUpdate( CoreLocationData locationData )
  {
    if (firstUpdate == 0)
    {
      lastLocationData = locationData;
    }

    double newDistance = DistanceBetweenPlaces(lastLocationData.longitude, lastLocationData.latitude, locationData.longitude, locationData.latitude);
    double angleToMove = AngleBetweenPlaces(lastLocationData.latitude, lastLocationData.longitude, locationData.latitude, locationData.longitude);
    double angleToMoveRadians = Deg2Rad(angleToMove);
    double newX = (newDistance * Math.Sin(angleToMoveRadians));
    double newZ = (newDistance * Math.Cos(angleToMoveRadians));
    float newXfloat = System.Convert.ToSingle(newX) * -1;
    float newZfloat = System.Convert.ToSingle(newZ) * -1;

    Debug.Log(string.Format("new x coordinate should be {0} and z should be {1}", newXfloat, newZfloat));

    currentVector = this.gameObject.transform.position;
    this.gameObject.transform.position = new Vector3((currentVector.x + newXfloat),0, (currentVector.z + newZfloat));
    lastLocationData = locationData;
    firstUpdate = 1;
  }

  public static double DistanceBetweenPlaces(
    double lon1,
    double lat1,
    double lon2,
    double lat2)
  {
    double phi1 = Deg2Rad(lat1);
    double phi2 = Deg2Rad(lat2);
    double deltaLamdba = Deg2Rad(lon2 - lon1);
    double d = Math.Acos(
      (Math.Sin(phi1) * Math.Sin(phi2)) + 
      (Math.Cos(phi1) * Math.Cos(phi2) * Math.Cos(deltaLamdba)));

    return d * RATIO;
  }

  public static double Deg2Rad(double degrees)
  {
    return degrees * (Math.PI / 180.0);
  }

  public static double Rad2Deg(double radians)
  {
    return radians * (180.0 / Math.PI);
  }

  public double AngleBetweenPlaces(double lat1, double lon1, double lat2, double lon2)
  {
    var newLat1 = Deg2Rad(lat1);
    var newLat2 = Deg2Rad(lat2);
    var dLon = Deg2Rad(lon2) - Deg2Rad(lon1);
    var y = Math.Sin(dLon) * Math.Cos(newLat2);
    var x = Math.Cos(newLat1) * Math.Sin(newLat2) - Math.Sin(newLat1) * Math.Cos(newLat2) * Math.Cos(dLon);
    var brng = Math.Atan2(y, x);
    return (Rad2Deg(brng) + 360) % 360;
  }
}

Answer 1

有时您使用 System.Math.PI，有时您使用 PIx = 3.141592653589793 - 这是什么原因？另外，RADIO 是什么，根据它的使用，我认为它是地球的平均半径(以公里为单位)，但该值已经过时了。

DistanceBetweenPlaces 方法也有一些错误，无论如何，请尝试以下操作，如果您对准确性有疑问，那么我会使用 Vincenty's formulae ，否则坚持使用简单的余弦球面定律。

// Earths Mean Radius in Kilometres?
public const double RADIO = 6371;

public static double DistanceBetweenPlaces(
    double lon1,
    double lat1,
    double lon2,
    double lat2)
{
  double phi1 = Deg2Rad(lat1);
  double phi2 = Deg2Rad(lat2);
  double deltaLamdba = ConvertDegreesToRadians(lon2 - lon1);
  double d = Math.Acos((Math.Sin(phi1) * Math.Sin(phi2)) + (Math.Cos(phi1) * Math.Cos(phi2) * Math.Cos(deltaLamdba)));
  return d * RADIO;

}

public static double Deg2Rad(double degrees)
{
    return degrees == 0 ? degrees : (degrees * Math.PI / 180.0);
}

另外，查看这个用于处理测地线数据的重要资源

http://www.movable-type.co.uk/scripts/latlong.html