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判断经纬度是否在中国(转)

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point, go, TI, IO, TE
   最近在做一个上位机,需要用得到地图显示并修正,看到一个不错的帖子,分享一下。
由于某些原因,国内地图总会有些偏移。虽说这是个相对偏移,但总会对需要坐标定位的应用造成几百米的漂移。若定位坐标在国外,则不会存在此问题。因此我们需要判别当前坐标是否在国内,然后决定是否进行坐标修正。
[size=13.3333px]根据国家行政边界判定
[size=13.3333px]      由于国家行政边界是由多个简单多边形组成的。对多个多边形进行命中测试 (Hit Testing),只要其中一个多边形测试成功,则表示整个命中测试成功。但多边形的命中测试有些麻烦,更简单的方法是判别点是否在多边形内(Point in polygon(PIP))。这些算法中简单高效的莫过于是光线投射算法 (Ray casting algorithm)
[size=13.3333px]      光线投射算法的要义是:在二维空间的任意一点射出一条射线,射线穿过多边形边界奇数次则这个点在多边形内,否则在多边形外。此方法适用于复杂多边形。实现此算法往往会限制射线的方向是向右的,这样的好处是简化了许多计算。此算法的一个实现参考1987年Paul Bourke教授所写“Determining if a point lies on the interior of a polygon”的Solution 1。
[size=13.3333px]      在 Windows Phone 7 中的实现,首先需要获取到国家行政边界的WGS84坐标数据。Alexey Strakh(链接有恶意软件警告)所开发的gMaps应用中包含了此边界数据。因此,自己可以把数据抠出来。抠出的数据由四部分组成我国的行政边界:大陆、台湾省、海南省、崇明岛。此数据相对来说比较准确,但是边界附近误差较大。每次判别坐标是否在此区域内的计算次数较多,大约需要几百次的几何计算。
[size=13.3333px]
[size=13.3333px]
#region polygon

List<Point[]> polygon = new List<Point[]>();

private void InitPolygon()
{
    polygon.Add(new Point[]  //Mainland
    {
        new Point(27.32083, 88.91693),
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        new Point(28.00805, 88.83575),
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        new Point(28.11166, 86.69527),
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        new Point(30.385, 81.42623),
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        new Point(30.20435, 81.02536),
        new Point(30.57552, 80.207),
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        new Point(22.69972, 114.5208),
        new Point(22.50423, 114.6136),
        new Point(22.55004, 114.2223),
        new Point(22.42993, 114.3885),
        new Point(22.26056, 114.2961),
        new Point(22.36736, 113.9056),
        new Point(22.50874, 114.0337),
        new Point(22.47444, 113.8608),
        new Point(22.83458, 113.606),
        new Point(23.05027, 113.5253),
        new Point(23.11724, 113.8219),
        new Point(23.05083, 113.4793),
        new Point(22.87986, 113.3629),
        new Point(22.54944, 113.5648),
        new Point(22.18701, 113.5527),
        new Point(22.56701, 113.1687),
        new Point(22.17965, 113.3868),
        new Point(22.04069, 113.2226),
        new Point(22.20485, 113.0848),
        new Point(21.8693, 112.94),
        new Point(21.96472, 112.824),
        new Point(21.70139, 112.2819),
        new Point(21.91611, 111.8921),
        new Point(21.75139, 111.9669),
        new Point(21.77819, 111.6762),
        new Point(21.61264, 111.7832),
        new Point(21.5268, 111.644),
        new Point(21.52528, 111.0285),
        new Point(21.21138, 110.5328),
        new Point(21.37322, 110.3944),
        new Point(20.84381, 110.1594),
        new Point(20.84083, 110.3755),
        new Point(20.64, 110.3239),
        new Point(20.48618, 110.5274),
        new Point(20.24611, 110.2789),
        new Point(20.2336, 109.9244),
        new Point(20.4318, 110.0069),
        new Point(20.92416, 109.6629),
        new Point(21.44694, 109.9411),
        new Point(21.50569, 109.6605),
        new Point(21.72333, 109.5733),
        new Point(21.49499, 109.5344),
        new Point(21.39666, 109.1428),
        new Point(21.58305, 109.1375),
        new Point(21.61611, 108.911),
        new Point(21.79889, 108.8702),
        new Point(21.59888, 108.7403),
        new Point(21.93562, 108.4692),
        new Point(21.59014, 108.5125),
        new Point(21.68999, 108.3336),
        new Point(21.51444, 108.2447),
        new Point(21.54241, 107.99),
        new Point(21.66694, 107.7831),
        new Point(21.60526, 107.3627),
        new Point(22.03083, 106.6933),
        new Point(22.45682, 106.5517),
        new Point(22.76389, 106.7875),
        new Point(22.86694, 106.7029),
        new Point(22.91253, 105.8771),
        new Point(23.32416, 105.3587),
        new Point(23.18027, 104.9075),
        new Point(22.81805, 104.7319),
        new Point(22.6875, 104.3747),
        new Point(22.79812, 104.1113),
        new Point(22.50387, 103.9687),
        new Point(22.78287, 103.6538),
        new Point(22.58436, 103.5224),
        new Point(22.79451, 103.3337),
        new Point(22.43652, 103.0304),
        new Point(22.77187, 102.4744),
        new Point(22.39629, 102.1407),
        new Point(22.49777, 101.7415),
        new Point(22.20916, 101.5744),
        new Point(21.83444, 101.7653),
        new Point(21.14451, 101.786),
        new Point(21.17687, 101.2919),
        new Point(21.57264, 101.1482),
        new Point(21.76903, 101.099),
        new Point(21.47694, 100.6397),
        new Point(21.43546, 100.2057),
        new Point(21.72555, 99.97763),
        new Point(22.05018, 99.95741),
        new Point(22.15592, 99.16785),
        new Point(22.93659, 99.56484),
        new Point(23.08204, 99.5113),
        new Point(23.18916, 98.92747),
        new Point(23.97076, 98.67991),
        new Point(24.16007, 98.89073),
        new Point(23.92999, 97.54762),
        new Point(24.26055, 97.7593),
        new Point(24.47666, 97.54305),
        new Point(24.73992, 97.55255),
        new Point(25.61527, 98.19109),
        new Point(25.56944, 98.36137),
        new Point(25.85597, 98.7104),
        new Point(26.12527, 98.56944),
        new Point(26.18472, 98.73109),
        new Point(26.79166, 98.77777),
        new Point(27.52972, 98.69699),
        new Point(27.6725, 98.45888),
        new Point(27.54014, 98.31992),
        new Point(28.14889, 98.14499),
        new Point(28.54652, 97.55887),
        new Point(28.22277, 97.34888),
        new Point(28.46749, 96.65387),
        new Point(28.35111, 96.40193),
        new Point(28.525, 96.34027),
        new Point(28.79569, 96.61373),
        new Point(29.05666, 96.47083),
        new Point(28.90138, 96.17532),
        new Point(29.05972, 96.14888),
        new Point(29.25757, 96.39172),
        new Point(29.46444, 96.08315),
        new Point(29.03527, 95.38777),
        new Point(29.33346, 94.64751),
        new Point(29.07348, 94.23456),
        new Point(28.6692, 93.96172),
        new Point(28.61876, 93.35194),
        new Point(28.3193, 93.22205),
        new Point(28.1419, 92.71044),
        new Point(27.86194, 92.54498),
        new Point(27.76472, 91.65776),
        new Point(27.945, 91.66277),
        new Point(28.08111, 91.30138),
        new Point(27.96999, 91.08693),
        new Point(28.07958, 90.3765),
        new Point(28.24257, 90.38898),
        new Point(28.32369, 89.99819),
        new Point(28.05777, 89.48749),
        new Point(27.32083, 88.91693)
    });
    polygon.Add(new Point[]  //Taiwan
    {
        new Point(25.13474, 121.4441),
        new Point(25.28361, 121.5632),
        new Point(25.00722, 122.0004),
        new Point(24.85028, 121.8182),
        new Point(24.47638, 121.8397),
        new Point(23.0875, 121.3556),
        new Point(21.92791, 120.7196),
        new Point(22.31277, 120.6103),
        new Point(22.54044, 120.3071),
        new Point(23.04437, 120.0539),
        new Point(23.61708, 120.1112),
        new Point(25.00166, 121.0017),
        new Point(25.13474, 121.4441)
    });
    polygon.Add(new Point[]  //Hainan
    {
        new Point(19.52888, 110.855),
        new Point(19.16761, 110.4832),
        new Point(18.80083, 110.5255),
        new Point(18.3852, 110.0503),
        new Point(18.39152, 109.7594),
        new Point(18.19777, 109.7036),
        new Point(18.50562, 108.6871),
        new Point(19.28028, 108.6283),
        new Point(19.76, 109.2939),
        new Point(19.7236, 109.1653),
        new Point(19.89972, 109.2572),
        new Point(19.82861, 109.4658),
        new Point(19.99389, 109.6108),
        new Point(20.13361, 110.6655),
        new Point(19.97861, 110.9425),
        new Point(19.63829, 111.0215),
        new Point(19.52888, 110.855)
    });
    polygon.Add(new Point[]  //Chongming
    {
        new Point(31.80054, 121.2039),
        new Point(31.49972, 121.8736),
        new Point(31.53111, 121.5464),
        new Point(31.80054, 121.2039)
    });
}
private bool IsInsideChina(GeoCoordinate positionToCheck)
{
    if (positionToCheck == null || positionToCheck.IsUnknown)
        return false;
    return polygon.Any(s => IsInsidePolygon(s, positionToCheck.Latitude, positionToCheck.Longitude));
}
private bool IsInsidePolygon(Point[] poly, double x, double y)
{
    var index = 0;
    var inside = false;
    var prePoint = poly[0];
    for (index = 1; index < poly.Length; index++)
    {
        var nextPoint = poly[index];
        if (y > Math.Min(prePoint.Y, nextPoint.Y)
            && y <= Math.Max(prePoint.Y, nextPoint.Y)
            && x <= Math.Max(prePoint.X, nextPoint.X)
            && prePoint.Y != nextPoint.Y)
        {
            double xinters = (y - prePoint.Y) * (nextPoint.X - prePoint.X) / (nextPoint.Y - prePoint.Y) + prePoint.X;
            if (prePoint.X == nextPoint.X || x <= xinters)
                inside ^= true;
        }
        prePoint = nextPoint;
    }
    return inside;
}

private void MainPage_Loaded(object sender, RoutedEventArgs e)
{
    InitPolygon();
    foreach (var points in polygon)
    {
        var poly = new MapPolyline();
        poly.Locations = new LocationCollection();
        for (int i = 0; i < points.Length; i++)
        {
            poly.Locations.Add(new GeoCoordinate(points[i].X, points[i].Y));
        }
        poly.Stroke = new SolidColorBrush(Colors.Red);
        myMap.Children.Add(poly);
    }
    myMap.SetView(new GeoCoordinate(39.4916649164344, 108.745576123357), 3.7090892722116307);
}

#endregion

相关帖子

沙发
gaochy1126|  楼主 | 2019-3-14 10:45 | 只看该作者
这个判断的超级不错,就是执行的速度慢一些,相对于电脑来说,没有什么问题

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板凳
Xy201207| | 2019-3-14 10:52 | 只看该作者
弱弱的问一下 这么多 new Point()能不能用一个循环加一个结构体数组代替

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地板
gaochy1126|  楼主 | 2019-3-14 12:43 | 只看该作者
Xy201207 发表于 2019-3-14 10:52
弱弱的问一下 这么多 new Point()能不能用一个循环加一个结构体数组代替 ...

可以,add可以。这个直接写出一个库直接调用,就行。        

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5
gaochy1126|  楼主 | 2019-3-31 13:51 | 只看该作者
有些人用不了这个代码,可以使用Gmap,这个可以使用的,超级不错。               

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6
linqing171| | 2019-4-9 19:41 | 只看该作者
这些point所有相邻的点连线,要探测的点和北京如果在线的两边,那么计数为1。

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7
linqing171| | 2019-4-9 19:42 | 只看该作者
如果计数加起来是奇数,那么就在外面了。这个算法有点傻,但是结果是对的。

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8
gaochy1126|  楼主 | 2019-4-11 16:09 | 只看该作者
linqing171 发表于 2019-4-9 19:42
如果计数加起来是奇数,那么就在外面了。这个算法有点傻,但是结果是对的。 ...

方法经过验证,可行。也没有要求太高,能用就行,当时一个地图显示上位机用到的

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9
gaochy1126|  楼主 | 2019-4-30 21:43 | 只看该作者
最近在网上看到一个帖子是直接生产边界的。               

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10
gaochy1126|  楼主 | 2019-4-30 21:43 | 只看该作者
国家行政边界可以直接有百度地图产生,然后画图实现。

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11
gaochy1126|  楼主 | 2019-5-31 21:43 | 只看该作者
国内地图 会有些偏移,国外的不需要的。正常显示就可以了。                 

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