** Next:** CONVERT EXAMPLES
** Up:** GREG2 Language Internal Help
** Previous:** ARROW
** Contents**
** Index**

##

CONVERT

[GREG2\]CONVERT A0 D0 [Angle] [/TYPE Ptype] [/UNIT Unit] [/SYSTEM
EQU|GAL [Equinox]] [/VARIABLE Var_X Var_Y]
The command converts coordinates in a given projection and coordinate
system to GREG current ones:
* Input:
- Coordinates are found in Var_X and Var_Y if the option /VARIABLE
is present, else buffers X and Y are used. Var_X and Var_Y must be
DOUBLE precision, writeable, 1-dimensional arrays. If input pro-
jection type is NONE, values are absolute spherical coordinates.
Else they are offsets from the projection center.
- The unit of coordinates can be set with the option /UNIT with the
argument SECOND, MINUTE, DEGREE, or RADIAN. Default is current
Greg angle unit (see HELP G\SET ANGLE_UNIT).
- Input coordinate system is set with the option /SYSTEM EQU|GAL
[Equinox]. Default equinox is 2000 if system is Equatorial.
- Input projection is defined by CONVERT A0 D0 [Angle] [/TYPE
Ptype]. A0 and D0 are the coordinates of the projection center
(reference of the offset coordinates). They are relevant except
for the NONE projection. Format is degrees in sexagesimal strings
(A0 is hour angle if input system is EQUATORIAL). Angle, if rele-
vant, must be set in degrees. Supported types can be found with
CONVERT /TYPE ?. Default is NONE.
* Output:
- Converted coordinates are saved in the input variables (overwrit-
ten). If the current Greg projection is NONE, values are absolute
spherical coordinates. Else they are offsets from the current Greg
projection center.
- The unit of output coordinates is always natural units (i.e. the
equivalent of Radians after reprojection).
- Output coordinate system is the current Greg one (see SHOW SYSTEM
and HELP SET SYSTEM).
- Output projection (center and type) is the current Greg one (see
HELP PROJECTION).
There is no provision for "hidden" parts which are treated exactly as
visible ones.

**Subsections**

Gildas manager
2020-09-28