我目前正在抓取用于定义here所见多边形的KML。
我使用算法detailed in this answer来确定该点是否在多边形内。
我遇到的问题是,如果该点位于多边形的空白部分内,如下所示。
如果我通过印第安纳波利斯的坐标(箭头所示),算法仍然会说该点在浅绿色多边形内,这是假的。
当我使用定义上图的KML传递印第安纳波利斯的坐标时,这些就是结果。
string(22) "39.7774501,-86.1090119" 39.7774501,-86.1090119 is outside Marginal Risk
string(22) "39.7774501,-86.1090119" 39.7774501,-86.1090119 is outside Marginal Risk
string(22) "39.7774501,-86.1090119" 39.7774501,-86.1090119 is outside Slight Risk
string(22) "39.7774501,-86.1090119" 39.7774501,-86.1090119 is outside Marginal Risk
string(22) "39.7774501,-86.1090119" 39.7774501,-86.1090119 is outside Marginal Risk
string(22) "39.7774501,-86.1090119" 39.7774501,-86.1090119 is outside Marginal Risk
string(22) "39.7774501,-86.1090119" 39.7774501,-86.1090119 is outside Marginal Risk
string(22) "39.7774501,-86.1090119" 39.7774501,-86.1090119 is outside Marginal Risk
string(22) "39.7774501,-86.1090119" 39.7774501,-86.1090119 is outside Marginal Risk
string(22) "39.7774501,-86.1090119" 39.7774501,-86.1090119 is outside Marginal Risk
string(22) "39.7774501,-86.1090119" 39.7774501,-86.1090119 is outside Marginal Risk
string(22) "39.7774501,-86.1090119" 39.7774501,-86.1090119 is outside Marginal Risk
string(22) "39.7774501,-86.1090119" 39.7774501,-86.1090119 is outside Slight Risk
string(22) "39.7774501,-86.1090119" 39.7774501,-86.1090119 is outside Marginal Risk
string(22) "39.7774501,-86.1090119" 39.7774501,-86.1090119 is outside Marginal Risk
string(22) "39.7774501,-86.1090119" 39.7774501,-86.1090119 is inside General Thunder
是否有人知道如何修改算法才能正常工作?
答案 0 :(得分:0)
绿色边界内的点是,但您只想用另一个多边形覆盖它。
假设您有多个多边形,可能值得跟踪多边形是否有阴影(True
)或没有阴影(False
),或者根据您的算法实际存在的其他组合确实
将着色状态作为参数传递到test
和pointInPolygon
函数(类似函数test($lat, $lng, $shaded)
)中,如果pointInPolygon
则反转$shaded
的输出是False
。
function pointInPolygon($p, $polygon, $shaded) {
//if you operates with (hundred)thousands of points
//rest of code
$output = $c%2!=0;
if (!$shaded) { //if the area is not shaded, negate the output
return !$output;
} else {
return $output;
}
}
要找到外部循环,请创建一个多边形数组,然后迭代,检查其中的所有组合(使用您已有的算法)。检查一个点到一个完整的其他多边形应该工作。从不在其他内部的多边形将是外部循环(阴影)。所有其他人都在里面,倒置而不是阴影。
当然,这是假设循环永远不会跨越自己。
您需要使用算法测试所有折线中的点。如果它在外部循环内,而不在任何内部循环内,则为阴影;如果它在外部循环内,并且在内部循环内,则它没有阴影。