【百度地图】获取某个覆盖物的总面积 

  1 //参数是一个百度类型的多边形覆盖物
  2 function getArea(polygon){
  3 
  4   // 检查类型：既不是百度类型的范围又不是数组类型的数据，直接返回0
  5   if (!(polygon instanceof BMap.Polygon) && !(polygon instanceof Array)) {
  6           return 0;
  7   }
  8 
  9    //如果是百度类型的，得到点集合，不是的话，另说。
 10    var pts = new Array();
 11    if (polygon instanceof BMap.Polygon) {
 12         pts = polygon.getPath();
 13    }
 14 
 15    //判断数组的长度，如果是小于3的话，不构成面，无法计算面积
 16    if (pts.length < 3) {
 17           return 0;
 18    }
 19 
 20    var totalArea = 0;// 初始化总面积
 21    var LowX = 0.0; 
 22    var LowY = 0.0; 
 23    var MiddleX = 0.0;
 24    var MiddleY = 0.0;
 25    var HighX = 0.0;
 26    var HighY = 0.0;
 27    var AM = 0.0;
 28    var BM = 0.0;
 29    var CM = 0.0;
 30    var AL = 0.0;
 31    var BL = 0.0;
 32    var CL = 0.0;
 33    var AH = 0.0;
 34    var BH = 0.0;
 35    var CH = 0.0;
 36    var CoefficientL = 0.0;
 37    var CoefficientH = 0.0;
 38    var ALtangent = 0.0;
 39    var BLtangent = 0.0;
 40    var CLtangent = 0.0;
 41    var AHtangent = 0.0;
 42    var BHtangent = 0.0;
 43    var CHtangent = 0.0;
 44    var ANormalLine = 0.0;
 45    var BNormalLine = 0.0;
 46    var CNormalLine = 0.0;
 47    var OrientationValue = 0.0;
 48    var AngleCos = 0.0;
 49    var Sum1 = 0.0;
 50    var Sum2 = 0.0;
 51    var Count2 = 0;
 52    var Count1 = 0;
 53    var Sum = 0.0;
 54    var Radius = 6378137.0;// ,WGS84椭球半径
 55    var Count = pts.length;
 56     for ( var i = 0; i < Count; i++) {
 57           if (i == 0) {
 58               LowX = pts[Count - 1].lng * Math.PI / 180;
 59               LowY = pts[Count - 1].lat * Math.PI / 180;
 60               MiddleX = pts[0].lng * Math.PI / 180;
 61               MiddleY = pts[0].lat * Math.PI / 180;
 62               HighX = pts[1].lng * Math.PI / 180;
 63               HighY = pts[1].lat * Math.PI / 180;
 64           } else if (i == Count - 1) {
 65               LowX = pts[Count - 2].lng * Math.PI / 180;
 66               LowY = pts[Count - 2].lat * Math.PI / 180;
 67               MiddleX = pts[Count - 1].lng * Math.PI / 180;
 68               MiddleY = pts[Count - 1].lat * Math.PI / 180;
 69               HighX = pts[0].lng * Math.PI / 180;
 70               HighY = pts[0].lat * Math.PI / 180;
 71           } else {
 72               LowX = pts[i - 1].lng * Math.PI / 180;
 73               LowY = pts[i - 1].lat * Math.PI / 180;
 74               MiddleX = pts[i].lng * Math.PI / 180;
 75               MiddleY = pts[i].lat * Math.PI / 180;
 76               HighX = pts[i + 1].lng * Math.PI / 180;
 77               HighY = pts[i + 1].lat * Math.PI / 180;
 78           }
 79           AM = Math.cos(MiddleY) * Math.cos(MiddleX);
 80           BM = Math.cos(MiddleY) * Math.sin(MiddleX);
 81           CM = Math.sin(MiddleY);
 82           AL = Math.cos(LowY) * Math.cos(LowX);
 83           BL = Math.cos(LowY) * Math.sin(LowX);
 84           CL = Math.sin(LowY);
 85           AH = Math.cos(HighY) * Math.cos(HighX);
 86           BH = Math.cos(HighY) * Math.sin(HighX);
 87           CH = Math.sin(HighY);
 88           CoefficientL = (AM * AM + BM * BM + CM * CM)/ (AM * AL + BM * BL + CM * CL);
 89           CoefficientH = (AM * AM + BM * BM + CM * CM)/ (AM * AH + BM * BH + CM * CH);
 90           ALtangent = CoefficientL * AL - AM;
 91           BLtangent = CoefficientL * BL - BM;
 92           CLtangent = CoefficientL * CL - CM;
 93           AHtangent = CoefficientH * AH - AM;
 94           BHtangent = CoefficientH * BH - BM;
 95           CHtangent = CoefficientH * CH - CM;
 96           AngleCos = (AHtangent * ALtangent + BHtangent * BLtangent + CHtangent* CLtangent)/ (Math.sqrt(AHtangent * AHtangent + BHtangent* BHtangent + CHtangent * CHtangent) * Math.sqrt(ALtangent * ALtangent + BLtangent* BLtangent + CLtangent * CLtangent));
 97           AngleCos = Math.acos(AngleCos);
 98           ANormalLine = BHtangent * CLtangent - CHtangent * BLtangent;
 99           BNormalLine = 0 - (AHtangent * CLtangent - CHtangent* ALtangent);
100           CNormalLine = AHtangent * BLtangent - BHtangent * ALtangent;
101           if (AM != 0)
102               OrientationValue = ANormalLine / AM;
103           else if (BM != 0)
104               OrientationValue = BNormalLine / BM;
105           else
106               OrientationValue = CNormalLine / CM;
107           if (OrientationValue > 0) {
108               Sum1 += AngleCos;
109               Count1++;
110           } else {
111               Sum2 += AngleCos;
112               Count2++;
113           }
114       }
115 
116       var tempSum1, tempSum2;
117       tempSum1 = Sum1 + (2 * Math.PI * Count2 - Sum2);
118       tempSum2 = (2 * Math.PI * Count1 - Sum1) + Sum2;
119       if (Sum1 > Sum2) {
120           if ((tempSum1 - (Count - 2) * Math.PI) < 1)
121               Sum = tempSum1;
122           else
123               Sum = tempSum2;
124       } else {
125           if ((tempSum2 - (Count - 2) * Math.PI) < 1)
126               Sum = tempSum2;
127           else
128               Sum = tempSum1;
129       }
130       totalArea = (Sum - (Count - 2) * Math.PI) * Radius * Radius;
131 
132       return totalArea; // 返回总面积
133 }

 

posted @ 2017-10-26 15:40  朝雾轻寒  阅读(1760)  评论(0)  编辑  收藏  举报