Geo functions from SQL Server 2008 to C# (latitude and longitude points inside or outside polygon/map area)

问题

In SQL Server 2008 I have:

Declare @pointIn geometry
Declare @pointOut geometry
Declare @polygon geometry

SET @polygon = geometry::STGeomFromText('POLYGON((40 -9,40 -6,35 -6,35 -9,40 -9))', 4326)
SET @pointIn =  geometry::STGeomFromText('POINT (39 -8)', 4326)
SET @pointOut =  geometry::STGeomFromText('POINT (41 -3)', 4326)

select @polygon.STIntersects(@pointIn)
select @polygon.STIntersects(@pointOut)

And as expected I get results 1 and 0.

Now I am trying to bring the same code to C# using the library: Microsoft.SqlServer.Types.dll

Using the following code:

var p1lat = 40;
var p1long = -9;
var p2lat = 40;
var p2ong = -6;
var p3lat = 35;
var p3ong = -6;
var p4lat = 35;
var p4ong = -9;

var pILat = 39;
var pILong = -8;
var pOLat = 41;
var pOLong = -3;

System.Threading.Thread.CurrentThread.CurrentCulture = new System.Globalization.CultureInfo("en-US");
const string polygonFormat = "POLYGON(({0} {1},{2} {3},{4} {5},{6} {7},{0} {1}))";
var polygon = string.Format(polygonFormat, p1lat, p1long, p2lat, p2ong, p3lat, p3ong, p4lat, p4ong);
var geometryString = new SqlChars(new SqlString(polygon));
var area = SqlGeography.STPolyFromText(geometryString, 4326);
var pointIn = SqlGeography.Point(pILat, pILong, 4326);
var pointOut = SqlGeography.Point(pOLat, pOLong, 4326);

Console.WriteLine(area.STIntersects(pointIn));
Console.WriteLine(area.STIntersects(pointOut));

I always get False, False..... and it should be True, False

Could someone help in here?

Thank you

回答1:

SqlGeography.Point and SqlGeography.STPointFromText use different coordinate order. Try one of the following solutions to fix the issue:

• Swap coordinates in SqlGeography.Point method call;
• Create points using WKT syntax (SqlGeography.STPointFromText).

来源：https://stackoverflow.com/questions/9448054/geo-functions-from-sql-server-2008-to-c-sharp-latitude-and-longitude-points-ins