如何加快将经度转换为 SqlGeometry

本文关键字：SqlGeometry 转换 经度 何加快 | 更新日期: 2023-09-27 18:32:23

我有这个代码，它采用国家的几何形状和一组点，然后它只返回这些国家/地区的点：

public static IEnumerable<Point> RemovePointsOutsideBorders(IEnumerable<Point> points, IEnumerable<Country> countries)
{
    var cc = new List<Point>();
    var SPAT_REF_ID = 4326;
    foreach (var p in points)
    {
            var validText = new SqlChars(new SqlString(string.Format("POINT({0} {1})", p.Longitude, p.Latitude)));
            var geoPoint = SqlGeometry.STPointFromText(validText, SPAT_REF_ID);
        foreach (var c in countries)
        {
            if(c.Polygon.STIntersects(geoPoint))
            {
                cc.Add(p);
                break;
            }
        }
    }
    return cc;
}

目前它相当慢，大约有 4000 个点，具有双纬度/经度值，从它到 SqlGeometry 的转换很慢（大约需要 25 秒 - 我需要这个可能减少到一两秒）：

var s = new SqlChars(new SqlString(string.Format("POINT({0} {1})", p.Longitude, p.Latitude)));
var pGeo = SqlGeometry.STPointFromText(s, SPAT_REF_ID);

这样做只是因为 SqlGeometry.Point 采用 x，y 而不是纬度，长...关于如何加快速度的任何提示？

我已经知道可以减少SqlGeometry (c.Polygon)以加快速度，但是我无法控制。我所追求的是一种加快从经度/经度到SqlGeometry点的转换的方法。

如何加快将经度转换为 SqlGeometry

这是我最后想出的解决方案，它在半秒内完成了整个事情：

public static IEnumerable<Point> RemovePointsOutsideBorders(IEnumerable<Point> points, IEnumerable<Country> countries)
{
    // join all the country polygons into one (make a stamp)
    var allCountryPolygon = countries.Select(x => x.Polygon).UnionAll();
    // make a single geometry shape from our evenly spaced extent points (cookie dough)
    var pointsGeo = PointsToGeometry(points);
    // do an intersect (stamp country shape over extent based geometry)
    var cookieOfPoints = pointsGeo.STIntersection(allCountryPolygon);
    // how many points left inside? pick them all back out
    for (int n = 1; n <= cookieOfPoints.STNumPoints(); n++)
    {
        var insidePoint = cookieOfPoints.STPointN(n);
        yield return new Point
        {
            Longitude = insidePoint.STX.Value,
            Latitude = insidePoint.STY.Value
        };
    }
}
public static SqlGeometry PointsToGeometry(IEnumerable<Point> points)
{
    var bld = new SqlGeometryBuilder();
    bld.SetSrid(4326);
    bld.BeginGeometry(OpenGisGeometryType.MultiPoint);
    foreach (var p in points)
    {
        bld.BeginGeometry(OpenGisGeometryType.Point);
        bld.BeginFigure(p.Longitude, p.Latitude);
        bld.EndFigure();
        bld.EndGeometry();
    }
    bld.EndGeometry();
    return bld.ConstructedGeometry;
}
public static class ExtensionMethods
{
    /// <summary>
    /// Joins many geometries into one
    /// </summary>
    /// <param name="geometries">geometries to join</param>
    /// <returns>composite geometry</returns>
    public static SqlGeometry UnionAll(this IEnumerable<SqlGeometry> geometries)
    {
        var compositeGeometry = geometries.First();
        foreach (var g in geometries.Skip(1))
        {
            compositeGeometry = compositeGeometry.STUnion(g);
        }
        return compositeGeometry;
    }
}
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