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S2polygon.getCentroid seems wrong in some case?

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难度
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预计耗时
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新手友好度
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Issue 类型
缺陷
描述清晰度
基本清楚
活跃度
停滞
技术栈
java
领域
computer-graphics

调研方向

从提供的 S2Loop/S2Polygon 复现和 S2Polygon.getCentroid 调用开始，然后确认纬度/经度值如何变成 S2Point 实例。将返回的点与多边形的坐标和 contains 结果进行比较；完成标准是确定导致所报告的外部点的原因究竟是质心计算还是输入解释，并使用回归测试覆盖该问题。

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描述

I encountered a problem where the centroid seems wrong, i.e., the centroid is outside the polygon even when the polygon itself is a convex.

The code below plots a hexagon but the centroid seems to be way off, did I do anything wrong, thanks a lot for help?

  double[] coordinates = new double[]{
            47.167511,-122.1521,
            47.167568,-122.151952,
            47.167684,-122.151952,
            47.167746,-122.1521,
            47.167691,-122.152248,
            47.16757,-122.152248,
            47.167511,-122.1521,
    };
    List<S2Point> s2Points = new ArrayList<>();
    for (int i = 0; i < coordinates.length /2; i++) {
        double lat = coordinates[2 * i];
        double lng = coordinates[2 * i + 1];
        System.out.println(lat + "," + lng + ",");
        S2LatLng s2LatLng = S2LatLng.fromDegrees(lat, lng);
        s2Points.add(s2LatLng.toPoint());
    }
    S2Loop s2Loop  = new S2Loop(s2Points);
    s2Loop.normalize();
    S2Polygon s2Polygon = new S2Polygon(s2Loop);
    S2Point s2PolygonCentroid = s2Polygon.getCentroid();
    System.out.println("Center: " + s2PolygonCentroid.toDegreesString() + " in_polygon " + s2Polygon
            .contains(s2PolygonCentroid));

Output:
Center: (47.167557150782145, -122.15163675765044) in_polygon false

Kml file:

layer <Style id="style-polygon-normal"> ff000000 1.2000000476837158 4d000000 1 1 <![CDATA[<h3>$[name]</h3>]]> </Style> <Style id="style-polygon-highlight"> ff000000 1.7999999523162842 4d000000 1 1 <![CDATA[<h3>$[name]</h3>]]> </Style> normal #style-polygon-normal highlight #style-polygon-highlight <Style id="style-s2cell-normal"> ff000000 1.2000000476837158 4d000000 1 1 <![CDATA[<h3>$[name]</h3>]]> </Style> <Style id="style-s2cell-highlight"> ff000000 1.7999999523162842 4d000000 1 1 <![CDATA[<h3>$[name]</h3>]]> </Style> normal #style-s2cell-normal highlight #style-s2cell-highlight test test #style-polygon -122.15210000000002,47.167511 -122.151952,47.16756800000001 -122.15195200000002,47.16768400000001 -122.15210000000002,47.167746 -122.15224799999999,47.167691000000005 -122.15224799999999,47.16757 -122.15210000000002,47.167511 -122.15163675765044,47.167557150782145 screen shot 2017-11-01 at 11 19 06 pm
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