利用NPGSL和EntityFramework内核在PostGIS上实现几何到地理的转换

Question

select * from "Tags" where ST_Distance("Location",'POINT(31.233334 30.033333)'::geography) < 1000 ;

var tags = db.Tags.Where((tag) => tag.Location.Distance(point) < RangeInMeters )
                .Select(tag => new {
                    Id = tag.Id,
                    Title = tag.Title,
                    Coordinates = new double[]{tag.Location.X,tag.Location.Y},
                });

以下是标签位置定义

[Column(TypeName="geometry (point)")]
public Point Location{get;set;}

这里是“点”变量定义

var point = new Point(new Coordinate(Longitude,Latitude));
point.SRID = 4326;

Answer 1

将column属性更改为[column(typename=“Geography”）]。如果点已经是一个地理位置，你不需要石膏。使用NetTopologySuite查看空间映射中的示例。

来自doc示例：

public class City
{
    public int Id { get; set; }
    public string Name { get; set; }

    [Column(TypeName="geography")]
    public Point Location { get; set; }
}

var nearbyCities = context.Cities.Where(c => c.Location.Distance(somePoint) < 100);

您可以使用st_GeographyFromtext直接创建地理点。从PostGIS地理文档中，您可以用以下方法计算两点之间的距离（以米为单位）：

SELECT ST_Distance(
  ST_GeographyFromText('POINT(-118.4079 33.9434)'), -- Los Angeles (LAX)
  ST_GeographyFromText('POINT(2.5559 49.0083)')     -- Paris (CDG)
  );

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