[postgis-tickets] [PostGIS] #4888: st_azimuth geography calculation reslut mismatch version 3.1.1

[PostGIS]

#4888: st_azimuth geography calculation reslut mismatch version 3.1.1
---------------------+---------------------------
 Reporter:  gislars  |      Owner:  pramsey
     Type:  defect   |     Status:  new
 Priority:  medium   |  Milestone:  PostGIS 3.1.2
Component:  postgis  |    Version:  3.1.x
 Keywords:           |
---------------------+---------------------------
 I'm doing calculation of directions and with postgis version 3.1.1. I get
 different or wrong results. It depends on the direction.

 I created a test case:


 {{{
 SELECT ST_Azimuth('POINT(0 0)'::geography, 'POINT(0 1)'::geography) AS
 a_north,
        ST_Azimuth('POINT(0 0)'::geography, 'POINT(1 1)'::geography) AS
 a_northeast,
        ST_Azimuth('POINT(0 0)'::geography, 'POINT(1 0)'::geography) AS
 a_east,
        ST_Azimuth('POINT(0 1)'::geography, 'POINT(0 0)'::geography) AS
 a_north_reverse,
        ST_Azimuth('POINT(1 1)'::geography, 'POINT(0 0)'::geography) AS
 a_northeast_reverse,
        ST_Azimuth('POINT(1 0)'::geography, 'POINT(0 0)'::geography) AS
 a_east_reverse
 union all
 select
        ST_Azimuth('POINT(0 0)'::geometry, 'POINT(0 1)'::geometry) AS
 a_north,
        ST_Azimuth('POINT(0 0)'::geometry, 'POINT(1 1)'::geometry) AS
 a_northeast,
        ST_Azimuth('POINT(0 0)'::geometry, 'POINT(1 0)'::geometry) AS
 a_east,
        ST_Azimuth('POINT(0 1)'::geometry, 'POINT(0 0)'::geometry) AS
 a_north_reverse,
        ST_Azimuth('POINT(1 1)'::geometry, 'POINT(0 0)'::geometry) AS
 a_northeast_reverse,
        ST_Azimuth('POINT(1 0)'::geometry, 'POINT(0 0)'::geometry) AS
 a_east_reverse
 }}}

 the result:
 || a_north || a_northeast || a_east || a_north_reverse ||
 a_northeast_reverse || a_east_reverse  ||
 || 3.141592653589793 || 0.788680084525966  || 1.5707963267948966   ||
 3.141592653589793  || 5.494352906159104  || 4.71238898038469 ||
 || 0 || 0.7853981633974483  ||  1.5707963267948966  ||  3.141592653589793
 || 3.9269908169872423  ||  4.71238898038469 ||

 the same result but converted to degrees:
 || a_north || a_northeast || a_east || a_north_reverse ||
 a_northeast_reverse || a_east_reverse  ||
 || 180  || 45.18804022935888 || 90 || 180 || 314.80323267835513  || 270
 ||
 || 0  || 45  || 90 || 180 || 225.00000000000006  || 270 ||


 The first row is displaying the results for geography type, the second for
 geometry type.

 These are the results for postgis version 2.5.2
 || a_north || a_northeast || a_east || a_north_reverse ||
 a_northeast_reverse || a_east_reverse  ||
 || 0   || 45.18804022935888    || 90   || 180   || 225.19676732164487  ||
 -90 ||
 || 0   || 45  || 90   || 180  || 225.00000000000006 || -90 ||

 The value of a_northeast_reverse and a_north value type geography isn't
 correct, it should be 0 (a_north) or 225 (a_northeast_reverse).

 The other values are ok. The difference for a_east_reverse is 360
 degree/2pi, the change was introduced in #4718

 Am I doing something wrong here? I'm not seeing what the problem might be.
 I couldn't figure out if it is actual a postgis problem or proj problem.
 Could someone verify this or help me to get the correct values?

-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/4888>
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