Determining cardinal (compass) direction between p

问题:

Is there a way to know in SQL Server 2008R2 if a point is at the south,east,etc...of another point?

For example, I have an origin point(lat1,lng1) and I want to know where point(lat2,lng2) is located from that origin: north, west,etc...

I'm trying to construct a wind rose graph and this might be useful to me.

回答1:

In order to calculate the bearing between two coordinates while using the Geography type in SQL Server 2008 R2, you can use this function:

CREATE FUNCTION [dbo].[CalculateBearing] 
(
    @pointA as geography
    ,@pointB as geography
)

RETURNS decimal(18,12)

AS

    BEGIN

    -- Declare the return variable
    DECLARE @bearing decimal(18,12)

    -- Declare the local variables
    DECLARE @x decimal(18,12)
    DECLARE @y decimal(18,12)
    DECLARE @dLat decimal(18,12)
    DECLARE @dLong decimal(18,12)
    DECLARE @rLat1 decimal(18,12)
    DECLARE @rLat2 decimal(18,12)

    IF(@pointA.STIsEmpty() = 1 OR @pointB.STIsEmpty() = 1)
        set @bearing = null
    ELSE
        BEGIN

        -- Calculate delta between coordinates
        SET @dLat = RADIANS(@pointB.Lat - @pointA.Lat)
        SET @dLong = RADIANS(@pointB.Long - @pointA.Long)

        -- Calculate latitude as radians
        SET @rLat1 = RADIANS(@pointA.Lat)
        SET @rLat2 = RADIANS(@pointB.Lat)

        SET @y = SIN(@dLong)*COS(@rLat2)
        SET @x = COS(@rLat1)*SIN(@rLat2)-SIN(@rLat1)*COS(@rlat2)*COS(@dLong)

        IF (@x = 0 and @y = 0)
            SET @bearing = null
        ELSE
            BEGIN
                SET @bearing = CAST((DEGREES(ATN2(@y,@x)) + 360) as decimal(18,12)) % 360
            END
    END

    -- Return the result of the function
    RETURN @bearing

END

GO

And after this, you can use this function like this:

DECLARE @pointA as geography
DECLARE @pointB as geography

SET @pointA = geography::STGeomFromText('POINT(3 45)', 4326)
SET @pointB = geography::STGeomFromText('POINT(4 47)', 4326)

SELECT [dbo].[CalculateBearing](@pointA, @pointB)

UPDATE: Adding a schema

回答2:

I came up with a way of calculating the bearing using a fairly straightforward use of standard SQL functions. The ATAN function does most of the real work; the two CASE statements are just special case corrections. 1 is the source and 2 is the destination.

atan(([Longitude2]-[Longitude1])/(10e-10+[Latitude2]-[Latitude1]))*360/pi()/2
+case when [Latitude2]<[Latitude1] then 180 else 0 end
+case when [Longitude2]<[Longitude1] and [Latitude2]>[Latitude1] then 360 else 0 end

回答3:

This morning I had need for this functionality to provide the range and cardinal direction to users when searching for nearby orders in our system. I came to Nicolas's answer here and it got me most of the way there. I created a second function that uses Nicolas's to get myself an abbreviated cardinal direction (N, NE, E, etc) for my UI.

Using Nicolas's bearing calculation provided here combined with values from https://en.wikipedia.org/wiki/Points_of_the_compass to determine ranges for each cardinal direction,

CREATE FUNCTION [dbo].[CalculateCardinalDirection] 
(
    @pointA as geography
    ,@pointB as geography
)

RETURNS varchar(2)

AS
BEGIN
    DECLARE @bearing decimal(18,12)
    -- Bearing calculation provided by http://stackoverflow.com/a/14781032/4142441
    SELECT @bearing = dbo.CalculateBearing(@pointA, @pointB)

    RETURN CASE WHEN @bearing BETWEEN 0 AND 22.5 THEN 'N'
                WHEN @bearing BETWEEN 22.5 AND 67.5 THEN 'NE'
                WHEN @bearing BETWEEN 67.5 AND 112.5 THEN 'E'
                WHEN @bearing BETWEEN 112.5 AND 157.5 THEN 'SE'
                WHEN @bearing BETWEEN 157.5 AND 202.5 THEN 'S'
                WHEN @bearing BETWEEN 202.5 AND 247.5 THEN 'SW'
                WHEN @bearing BETWEEN 247.5 AND 292.5 THEN 'W'
                WHEN @bearing BETWEEN 292.5 AND 337.5 THEN 'NW'
                ELSE 'N' -- Catches NULL bearings and the 337.5 to 360.0 range
           END
END
GO

回答4:

If the points data type are "Geometry" (Like UTM Coordinate System), you may use the following formula:

DEGREES(ATAN((X2-X1)/(Y2-Y1)))
+case when Y2<Y1 then 180 else 0 end
+case when Y2>Y1 and X2<X1 then 360 else 0 end

Here is the schema for more clarification:

回答5:

X=X2-X1 and Y=Y2-Y1. A formula that gives the bearing clockwise from 0 (positive Y axis) to 360 degrees.

  f(X,Y)=180-90*(1+SIGN(Y))*(1-SIGN(X^2))-45*(2+SIGN(Y))*SIGN(X)-180/PI()*SIGN(Y*X)*ATAN((ABS(Y)-ABS(X))/(ABS(Y)+ABS(X)))