使用EF Core和NetTopologySuite的半径按区域搜索

使用 ProjNet4GeoAPI 包将过滤值的点映射到投影坐标系,并使用它们计算距离(以米为单位)。

using GeoAPI.CoordinateSystems.Transformations;
using Microsoft.EntityFrameworkCore;
using NetTopologySuite.Geometries;
using ProjNet.CoordinateSystems;
using ProjNet.CoordinateSystems.Transformations;
using System.Diagnostics;
using System.Linq;

namespace ConsoleApp7
{
    public class Location
    {
        public int Id { get; set; }
        public Point Point { get; set; }
    }
    public class Business
    {
        public int Id { get; set; }
        public Point Point { get; set; }
        public double Distance { get; set; }
    }
    public class MyDbContext : DbContext
    {
        public DbSet<Location> Locations { get; set; }
        public DbSet<Business> Businesses { get; set; }
        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseSqlServer("Server=DESKTOP-5PVJ0I5;Database=geog;Integrated Security=true;", 
                options => options.UseNetTopologySuite());

            base.OnConfiguring(optionsBuilder);
        }
    }
    class Program
    {
        static void Main(string[] args)
        {
            CoordinateTransformationFactory ctfac = new CoordinateTransformationFactory();

            var from = GeographicCoordinateSystem.WGS84;
            var to = ProjectedCoordinateSystem.WGS84_UTM(30, true);

            // convert points from one coordinate system to another
            ICoordinateTransformation trans = ctfac.CreateFromCoordinateSystems(from, to);

            var businessCoordinate = new GeoAPI.Geometries.Coordinate(-0.127758, 51.507351);
            var searchLocationCoordinate = new GeoAPI.Geometries.Coordinate(-0.142500, 51.539188);

            var mathTransform = trans.MathTransform;
            var businessLocation = mathTransform.Transform(businessCoordinate);
            var searchLocation = mathTransform.Transform(searchLocationCoordinate);

            // calculate distance in meters
            var dist = businessLocation.Distance(searchLocation); // 3687m


            // arrange db
            var dbContext = new MyDbContext();
            dbContext.Database.Migrate();

            var location = new Location()
            {
                Point = new Point(searchLocationCoordinate.X, searchLocationCoordinate.Y) {  SRID = 4326, }
            };

            // one business has radius to include location point
            var businessWithLocationInRadius = new Business()
            {
                Distance = 4000,
                Point = new Point(businessCoordinate.X, businessCoordinate.Y) { SRID = 4326, }
            };

            // and this one has too low range
            var businessWithLocationNOTInRadius = new Business()
            {
                Distance = 3500,
                Point = new Point(businessCoordinate.X, businessCoordinate.Y) { SRID = 4326, }
            };

            dbContext.Add(location);
            dbContext.Add(businessWithLocationInRadius);
            dbContext.Add(businessWithLocationNOTInRadius);

            dbContext.SaveChanges();

            var query = dbContext
                .Businesses
                .Where(x => x.Point.Distance(location.Point) <= x.Distance)
                .ToList()

                .Select(x => new
                {
                    Distance = searchLocation
                        .Distance(mathTransform.Transform(new GeoAPI.Geometries.Coordinate(x.Point.X, x.Point.Y))), // 3687m
                    Radius = x.Distance
                })
                
                .ToList();

            Debugger.Break();
        }
    }
}

参考: SRID Ignored during client operations :

NTS在操作期间忽略SRID值。它采用平面坐标系。这意味着,如果以经度和纬度为单位指定坐标,一些客户机评估的值(如距离、长度和面积)将以度为单位,而不是以米为单位。对于更有意义的值,在计算这些值之前,首先需要使用ProjNet4GeoAPI之类的库将坐标投影到另一个坐标系。

这是因为NetTopologySuite是一个。JTS拓扑套件的网络端口。参考: NetTopologySuite :

A.NET地理信息系统解决方案,该解决方案快速可靠。NET平台。NetTopologySuite是JTS拓扑套件提供的所有功能的直接端口:NTS将JTS暴露在“一个”中。NET方式,例如使用属性、索引器等。。。

JTS网站的一段摘录也解释了NTS的功能:“JTS拓扑套件是一个用于建模和操作二维线性几何体的API。它提供了许多几何谓词和函数。JTS符合开放式GIS联盟发布的SQL简单功能规范。”