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Geospatial functions

ST_AZIMUTH¶

Given a Point that represents the origin (the location of the observer) and a specified Point, returns the azimuth in radians. Both Points must be either GEOGRAPHY or GEOMETRY objects.

The azimuth is the angle between the two Points when the observer at the origin is facing the north (for GEOGRAPHY objects) or the Y-axis (for GEOMETRY objects). The angle is positive in the clockwise direction and is:

  • 0 for a line segment pointing north.

  • Ï€/2 for a line segment pointing east.

  • Ï€ for a line segment pointing south.

  • 3Ï€/2 for a line segment pointing west.

If the two Points are the same location, the function returns NULL.

For GEOGRAPHY objects, on spherical Earth, the formula described here is used to determine the azimuth.

Caution

Systems using an elliptical Earth model use a more complex algorithm for Azimuth, which occasionally yields significantly different results.

Syntax¶

ST_AZIMUTH( <geography_expression_for_origin> , <geography_expression_for_target> )
ST_AZIMUTH( <geometry_expression_for_origin> , <geometry_expression_for_target> )
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Arguments¶

geography_expression_for_origin

A GEOGRAPHY object that is a Point representing the origin (where the observer is located).

geography_expression_for_target

A GEOGRAPHY object that is a Point for which you want to calculate the azimuth.

geometry_expression_for_origin

A GEOMETRY object that is a Point representing the origin (where the observer is located).

geometry_expression_for_target

A GEOMETRY object that is a Point for which you want to calculate the azimuth.

Returns¶

Returns a value of type REAL that is the azimuth in radians.

Usage notes¶

  • If one of the input geospatial objects is not a Point, the function reports an error.

  • Returns NULL if one or both input points are NULL.

Examples¶

GEOGRAPHY examples¶

The following example returns the azimuth in radians for an origin Point (0, 1) and a target Point (0, 0):

SELECT ST_AZIMUTH(
    TO_GEOGRAPHY('POINT(0 1)'),
    TO_GEOGRAPHY('POINT(0 0)')
);
+---------------------------------+
|                     ST_AZIMUTH( |
|     TO_GEOGRAPHY('POINT(0 1)'), |
|      TO_GEOGRAPHY('POINT(0 0)') |
|                               ) |
|---------------------------------|
|                     3.141592654 |
+---------------------------------+
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The following example returns the azimuth in degrees for an origin Point (0, 1) and a target Point (1, 2):

SELECT DEGREES(ST_AZIMUTH(
    TO_GEOGRAPHY('POINT(0 1)'),
    TO_GEOGRAPHY('POINT(1 2)')
));
+---------------------------------+
|             DEGREES(ST_AZIMUTH( |
|     TO_GEOGRAPHY('POINT(0 1)'), |
|      TO_GEOGRAPHY('POINT(1 2)') |
|                              )) |
|---------------------------------|
|                    44.978182941 |
+---------------------------------+
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GEOMETRY examples¶

The following example returns the azimuth in radians for an origin Point (0, 1) and a target Point (0, 0):

SELECT ST_AZIMUTH(
    TO_GEOMETRY('POINT(0 1)', TO_GEOMETRY('POINT(0 0)')
);

+------------------------------------------------------------------+
| ST_AZIMUTH(TO_GEOMETRY('POINT(0 1)'), TO_GEOMETRY('POINT(0 0)')) |
|------------------------------------------------------------------|
| 3.141592654                                                      |
+------------------------------------------------------------------+
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The following example returns the azimuth in degrees for an origin Point (0, 1) and a target Point (0.707, 0.707):

SELECT ST_AZIMUTH(
    TO_GEOMETRY('POINT(0 0)', TO_GEOMETRY(0.707 0.707')
);

+-------------------------------------------------------------------------+
| ST_AZIMUTH(TO_GEOMETRY('POINT(0 0)'), TO_GEOMETRY('POINT(0.707 0.707')) |
|-------------------------------------------------------------------------|
| 0.7853981634                                                            |
+-------------------------------------------------------------------------+
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