A commonly used task is a coordinate transformation. With the parameters of a new coordinate system (plane) relative to an old one,
Ω
| longitude of the ascending node | angle between line of nodes and the zero point of longitude in the old plane. |
ω
| argument of pericenter | the angle from the ascending node to the position in the new plane. |
| i | inclination | angle between the new plane and the old plane. |
you can do a transformation of an object
object from an old into a new coordinate
system using:
object - strans 'ω, i,Ω'
or
object - strans (ω, i,Ω)
Otherwise, for a transformation of an object
object from the new into the old
coordinate system, use the operator +:
object + strans 'ω, i,Ω'
or
object + strans (ω, i,Ω)
Example 8.1. perihelion and aphelion coordinates of a comet's orbit
We are assuming the orbital elements of a comet are
Ω=30°, i=60° and ω=90°. We get the
spherical position of perihelion and aphelion with:
sql> SELECT set_sphere_output('DEG');
set_sphere_output
-------------------
SET DEG
(1 row)
sql> SELECT spoint '(0,0)' + strans '90d,60d,30d' AS perihelion;
perihelion
--------------
(120d , 60d)
(1 row)
sql> SELECT spoint '(180d,0)' + strans '90d,60d,30d' AS aphelion;
aphelion
---------------
(300d , -60d)
(1 row)