球体相关算法

小鱼儿 2024-04-19 11:14 73阅读 0赞

/** * 度换成弧度 * @param d 度 * @return 弧度 */
    function rad(d) { 
      return d * Math.PI / 180.0;
    }
     
    /** * 弧度换成度 * @param x 弧度 * @return 度 */
    function deg(x) { 
      return x * 180 / Math.PI;
    }
    
    /** * 计算另一点经纬度 * @param lnglat * 已知点经纬度 * @param brng * 方位角 ---- 正北方：000°或360° 正东方：090° 正南方：180° 正西方：270° * @param dist * 距离（米） */
     ADestinceAngle_B = function (lnglat, brng, dist) { 
        
        /* * 大地坐标系资料WGS-84 长半径a=6378137 短半径b=6356752.3142 扁率f=1/298.2572236 */
        var ct = { 
          a: 6378137,
          b: 6356752.3142,
          f: 1 / 298.257223563
        };
        var a = ct.a, b = ct.b, f = ct.f;
     
        var lng1 = lnglat.lng * 1;  //乘一（*1）是为了确保经纬度的数据类型为number
        var lat1 = lnglat.lat * 1;
     
        var s = dist;
        var alpha1 = rad(brng);
        var sinAlpha1 = Math.sin(alpha1);
        var cosAlpha1 = Math.cos(alpha1);
     
        var tanU1 = (1 - f) * Math.tan(rad(lat1));
        var cosU1 = 1 / Math.sqrt((1 + tanU1 * tanU1)), sinU1 = tanU1 * cosU1;
        var sigma1 = Math.atan2(tanU1, cosAlpha1);
        var sinAlpha = cosU1 * sinAlpha1;
        var cosSqAlpha = 1 - sinAlpha * sinAlpha;
        var uSq = cosSqAlpha * (a * a - b * b) / (b * b);
        var A = 1 + uSq / 16384 * (4096 + uSq * (-768 + uSq * (320 - 175 * uSq)));
        var B = uSq / 1024 * (256 + uSq * (-128 + uSq * (74 - 47 * uSq)));
     
        var sigma = s / (b * A), sigmaP = 2 * Math.PI;
        while (Math.abs(sigma - sigmaP) > 1e-12) { 
          var cos2SigmaM = Math.cos(2 * sigma1 + sigma);
          var sinSigma = Math.sin(sigma);
          var cosSigma = Math.cos(sigma);
          var deltaSigma = B * sinSigma * (cos2SigmaM + B / 4 * (cosSigma * (-1 + 2 * cos2SigmaM * cos2SigmaM) -
            B / 6 * cos2SigmaM * (-3 + 4 * sinSigma * sinSigma) * (-3 + 4 * cos2SigmaM * cos2SigmaM)));
          sigmaP = sigma;
          sigma = s / (b * A) + deltaSigma;
        }
     
        var tmp = sinU1 * sinSigma - cosU1 * cosSigma * cosAlpha1;
        var lat2 = Math.atan2(sinU1 * cosSigma + cosU1 * sinSigma * cosAlpha1,
          (1 - f) * Math.sqrt(sinAlpha * sinAlpha + tmp * tmp));
        var lambda = Math.atan2(sinSigma * sinAlpha1, cosU1 * cosSigma - sinU1 * sinSigma * cosAlpha1);
        var C = f / 16 * cosSqAlpha * (4 + f * (4 - 3 * cosSqAlpha));
        var L = lambda - (1 - C) * f * sinAlpha *
          (sigma + C * sinSigma * (cos2SigmaM + C * cosSigma * (-1 + 2 * cos2SigmaM * cos2SigmaM)));
        var revAz = Math.atan2(sinAlpha, -tmp);  // final bearing
        var lng_destina = lng1 * 1 + deg(L);
        
        var lnglat_destination = { lng: lng_destina, lat: deg(lat2)};
     
        return lnglat_destination;
      }
    
    // 根据经纬度计算两点的距离
    function getDistanceBy2Point( startPoint,  endPoint){ 
      var radLat1 = rad(startPoint.lat);
      var radLat2 = rad(endPoint.lat);
      var a = rad(startPoint.lat) - rad(endPoint.lat);
      var b = rad(startPoint.lng) - rad(endPoint.lng);
      var s = 2 * Math.asin(Math.sqrt(Math.pow(Math.sin(a/2),2) +
      Math.cos(radLat1)*Math.cos(radLat2)*Math.pow(Math.sin(b/2),2)));
      s = s * 6378137.0 ;// EARTH_RADIUS;
      s = Math.round(s * 10000) / 10000;
      return s; //return的距离单位为m
    }
    
    // 简单海拔计算
    function getAltSimply(startPoint, endPoint, subDist, totalDist){ 
      return subDist==0?startPoint.alt:startPoint.alt+(endPoint.alt-startPoint.alt) * subDist/totalDist;
    }
    
    // 根据经纬度获取方位角
    function getLineAngle( startPoint,  endPoint){ 
        var mathPI = 3.1415926535897931;
        var tmpValue = 0;
        var latStart = rad(startPoint.lat);//Y
        var lngStart = rad(startPoint.lng);//X
        var latEnd = rad(endPoint.lat);
        var lngEnd = rad(endPoint.lng);
        if (startPoint.lng == endPoint.lng || startPoint.lat == endPoint.lat)
        { 
            if (startPoint.lng == endPoint.lng)
            { 
                /// 经度相同
                return endPoint.lat >= startPoint.lat?0:180;
            }
            else
            { 
                /// 纬度相同
                return endPoint.lng >= startPoint.lng?90:270;
            }
        }
    
        var tmpValue = Math.sin(latStart) * Math.sin(latEnd) + Math.cos(latStart) * Math.cos(latEnd) * Math.cos(lngEnd - lngStart);
        var tmpValue = Math.sqrt(1 - tmpValue * tmpValue);
        var tmpValue = Math.cos(latEnd) * Math.sin(lngEnd - lngStart) / tmpValue;
        var resultAngle = Math.abs(Math.asin(tmpValue) * 180 / mathPI);
    
        if (endPoint.lng > startPoint.lng)
        { 
            if (endPoint.lat >= startPoint.lat)
            { 
                return resultAngle; /// 第一象限 
            }
            else
            { 
                return 180 - resultAngle;  /// 第二象限 
            }
        }
        else
        { 
            if (endPoint.lat >= startPoint.lat)
            { 
                return 360 - resultAngle; /// 第四象限
            }
            else
            { 
                return 180 + resultAngle; /// 第三象限
            }
        }
    }