Question

使用SQL Server 2012，以下查询一直告诉我，我正在寻找的点不在我正在使用的多边形内部，当我知道它时。在QGIS 2.2.0中使用相同的数据，我清楚地看到该点位于多边形内（截图）。

DECLARE @polygon GEOGRAPHY = GEOGRAPHY::STPolyFromText('POLYGON ((-111.0498046875 33.966142265597391, -110.9124755859375 33.472690192666633, -110.94268798828125 32.983324091837417, -111.7364501953125 32.680996432581921, -112.587890625 32.731840896865656, -113.0657958984375 33.307577130152978, -112.9010009765625 33.811102288647007, -112.32147216796875 34.1890858311723, -111.4453125 34.129994745824717, -111.0498046875 33.966142265597391))', 4326);
DECLARE @point GEOGRAPHY = GEOGRAPHY::STPointFromText('POINT (-112.0685317 33.4491407)', 4326);

SELECT  @point.STIsValid() AS [PointIsValid], --True
        @polygon.STIsValid() AS [PolygonIsValid], --True
        @point.STWithin(@polygon) AS [PointWithinPolygon], --False
        @point.STIntersects(@polygon) AS [PointIntersectsPolygon], --False
        @polygon.STContains(@point) AS [PolygonContainsPoint]; --False

我需要做什么让查询告诉我这个点在多边形中？我已经看到一些搜索结果谈论“方向”，但我不知道如何指定它。坐标从Google Maps JavaScript API捕获，并使用Entity Framework 6.1持久保存到数据库。

enter image description here

Answer 1

我认为你有Ring Orientation problem。您需要反转多边形的顺序：

using Microsoft.SqlServer.Types;
using System;
using System.Collections.Generic;
using System.Data.Spatial;
using System.Data.SqlTypes;

namespace SomeNamespace
{
  public static class DbGeographyHelper
  {
    // 4326 is most common coordinate system used by GPS/Maps
    // 4326 format puts LONGITUDE first then LATITUDE
    private static int _coordinateSystem = 4326;

    public static DbGeography CreatePolygon(string wktString)
    {
      // create polygon is same order as wktString
      var sqlGeography = SqlGeography
        .STGeomFromText(new SqlChars(wktString), _coordinateSystem)
        .MakeValid();

      // create the polygon in the reverse order
      var invertedSqlGeography = sqlGeography.ReorientObject();

      // which ever one is big is probably not the one you want
      if (sqlGeography.STArea() > invertedSqlGeography.STArea())
      {
        sqlGeography = invertedSqlGeography;
      }

      return DbSpatialServices.Default.GeographyFromProviderValue(sqlGeography);
    }
  }
}

Answer 2

@ Erik的答案是正确的，因为SQL Server排除了我在多边形中指定的区域。反转多边形修复了问题。他的代码是正确的，但我必须进行修改以适应我的用法，所以这里的代码适用于任何关心的人：

public static class DbGeographyExtensions {
    public static DbGeography PolygonFromGoogleMapsText(
        string wellKnownText,
        int coordinateSystemId) {
        SqlGeography geography = SqlGeography.STGeomFromText(new SqlChars(wellKnownText), coordinateSystemId).MakeValid();
        SqlGeography invertedGeography = geography.ReorientObject();

        if (geography.STArea() > invertedGeography.STArea()) {
            geography = invertedGeography;
        }

        return DbGeography.FromText(geography.ToString(), coordinateSystemId);
    }
}

我在尝试从@ Erik的代码返回时遇到异常，因此我使用了答案中的代码：Entity Framework: SqlGeography vs DbGeography

检查Point是否在Polygon内部不起作用

2 个答案: