sql-server-2008 - 使用 SqlGeographyBuilder 时“指定的输入不代表有效的地理实例”异常

Question

我编写了一个小应用程序，它从一系列 KML 文件中读取数据，然后使用以下代码将它们转换为 Microsoft.SqlServer.Types.SqlGeography 类型:

    private SqlGeography CreateGeographyFromKML( string kml, bool debug )
    {
        // use SqlGeographyBuilder to help create the SqlGeography type 
        var geographyBuilder = new SqlGeographyBuilder();

        // Get co-ordinates 
        var xml = XDocument.Parse(kml);
        var df = xml.Root.Name.Namespace;
        XElement coordinates = xml.Descendants(df + "coordinates").Single();

        // set the Spatial Reference Identifiers that will used to create the point 
        geographyBuilder.SetSrid(_srid);
        geographyBuilder.BeginGeography(OpenGisGeographyType.Polygon);

        var longLat = coordinates.Value.Split(' ').Select(c => new { Lat = Convert.ToDouble(c.Split(',')[1]), Long = Convert.ToDouble(c.Split(',')[0]) });

        Console.Write("Found {0} ", longLat.Count());

        foreach (var coord in longLat.Select((x, i) => new { Index = i, Value = x }))
        {
            if (coord.Index == 0)
            { // First point
                if ( debug ) Console.WriteLine("First point: {0},{1}", coord.Value.Lat, coord.Value.Long);
                geographyBuilder.BeginFigure(coord.Value.Lat, coord.Value.Long);
            }
            else
            { // Intermediate points
                if (debug) Console.WriteLine("Intermediate point: {0},{1}", coord.Value.Lat, coord.Value.Long);
                geographyBuilder.AddLine(coord.Value.Lat, coord.Value.Long);
            }

            if (coord.Index == longLat.Count() - 1 )
            { // Last point (Close polygon)     
                if (debug) Console.Write("Last point: ");

                // Check not already added
                if (longLat.Last().Lat == longLat.First().Lat && longLat.Last().Long == longLat.First().Long)
                {
                    if (debug) Console.Write("Already exists - not adding...");
                }
                else
                {
                    if (debug) Console.Write("{0},{1}", longLat.Last().Lat, longLat.Last().Long);
                    geographyBuilder.AddLine(longLat.Last().Lat, longLat.Last().Long);
                }

                geographyBuilder.EndFigure(); // End figure
            }
        }

        if (debug) Console.WriteLine();

        // close the figure and geography class 
        geographyBuilder.EndGeography();

        // get the geography builder to return the sqlgeography type 
        return geographyBuilder.ConstructedGeography;
    }

基本上，这段代码从 KML 文件中检索纬度/经度列表，然后遍历它们以创建一个多边形。

但是，我导入的某些 KML 文件失败，但出现以下异常:

System.ArgumentException was caught Message=24200: The specified input does not represent a valid geography instance.

这发生在以下行:return geographyBuilder.ConstructedGeography;

我找到了一些 reference to this exception ，但是在我发现他们在 SQL Server 中而不是在 C# 中遇到并处理此异常的情况下。

Answer 1

我遇到了同样的错误，但结果证明是多边形环方向问题。一个简单的翻转坐标数组顺序的问题就解决了。

为了说明，这失败并出现上述错误:

 select geography::STGeomFromText ('Polygon  ( (10 10, 10 20, 20 20, 20 10, 10 10))',4326)

这是可行的:

 select geography::STGeomFromText ('Polygon  ( (10 10, 20 10, 20 20, 10 20, 10 10))',4326)

请注意，我不是在一个点内翻转 x,y 对，而是翻转整个点数组的顺序(例如 {pt1, pt2, pt3, pt4, pt5} 变为 {pt5, pt4, pt3, pt2, pt1}