在開發與經緯度有關的項目時,通常需要將經緯度座標與3D引擎中的座標系進行互相換算。本次創新以Unity3D爲例,使用一系列算法將經緯度座標與3D座標系進行換算。
1.座標系分析(以Unity3D左手座標系爲例)
經緯度座標是描述球面上某個點的位置,若已知球體半徑(R)和球體中心點的3D座標(O)便可通過一些列計算的到3D座標系中的座標點(P)。
通過經度可以計算出 ∠AOB的度數
通過緯度可以計算出 ∠BOP的度數
經度轉3D座標公式:
X=R*Cos(∠BOP)*Cos(∠AOB)
Y=R*Cos(∠BOP)*Sin(∠AOB)
Z=R*(∠BOP)
經度轉3D座標公式:
∠BOP=Asin(Z/R)
∠AOB=Asin(Y/X)
2.具體實現:
座標轉換功能
using UnityEngine;
using System.Collections;
public class SaiGetLatLog : MonoBehaviour {
public Transform firstPoint; //Unity中左上點
public Transform secondPoint;//Unity中右下點
public SaiEarth firstSai;//地圖中對應的左上經緯度點
public SaiEarth secondSai;//地圖中對應的右下經緯度點
private float z_offset,x_offset,z_w_offset,x_w_offset;
private RaycastHit rayHit;
// Use this for initialization
void Start () {
InitBasicNum ();//初始化參數
}
// Update is called once per frame
void Update () {
if (Input.GetMouseButton (0) && Physics.Raycast (Camera.main.ScreenPointToRay (Input.mousePosition), out rayHit, Mathf.Infinity)) {
print ( getWorldPoint(firstSai).x+","+ getWorldPoint(firstSai).z);
}
}
void InitBasicNum()
{
firstSai = new SaiEarth (new Vector3 (116f, 23f, 9.27f), new Vector3 (39f, 55f, 15.74f));
secondSai = new SaiEarth (new Vector3(116f,23f,44.39f),new Vector3(39f,54f,44.27f));
z_offset = Mathf.Abs ((firstSai.latitude.x+firstSai.latitude.y/60+firstSai.latitude.z/3600) - (secondSai.latitude.x+secondSai.latitude.y/60+secondSai.latitude.z/3600));//地圖中的維度差
x_offset = Mathf.Abs ((firstSai.longitude.x+firstSai.longitude.y/60+firstSai.longitude.z/3600)-(secondSai.longitude.x+secondSai.longitude.y/60+secondSai.longitude.z/3600));//地圖中的經度差
z_w_offset = Mathf.Abs (firstPoint.localPosition.z - secondPoint.localPosition.z);//unity中的維度差
x_w_offset = Mathf.Abs (firstPoint.localPosition.x - secondPoint.localPosition.x);//unity中的經度差
}
Vector3 getWorldPoint(SaiEarth se)//由經緯度得到位置點
{
float tempX = (float)(se.longitude.x + se.longitude.y / 60 + se.longitude.z / 3600 - (secondSai.longitude.x + secondSai.longitude.y / 60 + secondSai.longitude.z / 3600));
float tempZ = (float)(se.latitude.x + se.latitude.y / 60 + se.latitude.z / 3600 - (secondSai.latitude.x + secondSai.latitude.y / 60 + secondSai.latitude.z / 3600));
float _tempX = (float)(tempX * x_w_offset / x_offset + secondPoint.localPosition.x);
float _tempZ = (float)(tempZ * z_w_offset / z_offset + secondPoint.localPosition.z);
return new Vector3((float)_tempX,0f,(float)_tempZ);
}
SaiEarth getLatLon(Vector3 curPoint)//由位置點得到經緯度
{
SaiEarth tempEarth = new SaiEarth();
float _z_offset = Mathf.Abs (curPoint.z - secondPoint.localPosition.z) * z_offset / z_w_offset;
float _x_offset = Mathf.Abs (curPoint.x - secondPoint.localPosition.x) * x_offset / x_w_offset;
float resultX = _x_offset + (secondSai.longitude.x + secondSai.longitude.y/60 + secondSai.longitude.z/3600);
float resultZ = _z_offset + (secondSai.latitude.x + secondSai.latitude.y/60 + secondSai.latitude.z/3600);
tempEarth.longitude = new Vector3 ((int)resultX, (int)((resultX - (int)resultX)*60),((resultX - (int)resultX)*60 - (int)((resultX - (int)resultX)*60))*60);
tempEarth.latitude = new Vector3 ((int)resultZ, (int)((resultZ - (int)resultZ)*60),((resultZ - (int)resultZ)*60 - (int)((resultZ - (int)resultZ)*60))*60);
return tempEarth;
}
}
using UnityEngine;
using System.Collections;
public class SaiEarth {
public Vector3 longitude;
public Vector3 latitude;
public SaiEarth()
{
}
public SaiEarth(Vector3 longitude,Vector3 latitude)
{
this.latitude = latitude;
this.longitude = longitude;
}
public string toString()
{
return "Lat:"+this.latitude + ",Long:" + this.longitude;
}
}