# AIPS HELP file for COORDINA in 31DEC19

### HELP SECTION

```COORDINA
Use:  An array adverb used to convey coordinate values as:
Xpos = abs(COOR(1)) + abs(COOR(2))/60 + abs(COOR(3))/3600
if any of COOR(1), COOR(2), COOR(3) < 0: Xpos = -Xpos
Ypos = abs(COOR(4)) + abs(COOR(5))/60 + abs(COOR(6))/3600
if any of COOR(4), COOR(5), COOR(6) < 0: Ypos = -Ypos
Note that, although these are most suited to RA, Dec in
sexagesimal notation, they can be used for any type of coordinate.
The units are standard units of the X and Y axes (e.g degrees,
m/sec, Hz, sec, etc.) except that right ascensions are in hours of
time.

It is normal in print to represent a declination between -1 and
0 degrees as -0d mm ss.s.  But if you type, e.g.
COORDINA = 14, 8, 23.3, -0, 14, 23
you will get a positive declination because there is no
difference numerically between -0 and +0.  You need to type
COORDINA = 14, 8, 23.3, -0, -14, 23
to get the desired negative coordinate.  BE VERY CAREFUL when
you type negative coordinates to use commas to separate the
values.  Otherwise the minus sign becomes a subtraction sign and
you do not get the desired values in the adverb.

Null value:  None, 0 means 0.

Verbs:
CODECIML....Convert between decimal and sexagesimal coordinate
values
COODEFIN....Define or modify an image axis coordinate description
COPIXEL.....Convert between physical and pixel coordinate values
COSTAR......Plot a symbol on the TV at the specified coordinate.
COTVLOD.....Load a TV image centered on the specified coordinate.
COWINDOW....Set BLC, TRC centered on a coordinate.
EPOCONV.....Convert between J2000 and B1950 coordinates
IMCENTER....Returns pixel position of sub-image centroid
IMPOS.......Displays celestial coordinates selected by the TV cursor
IMVAL.......Returns image intensity and coordinate at specified
pixel
MAXFIT......Returns pixel position and image intensity at a maximum
QIMVAL......Returns image intensity and coordinate at specified
pixel quietly

Build-in procedures:
TVFLUX......Displays coordinates and values selected with the TV
cursor
TVMAXFIT....Displays fit pixel positions and intensity at maxima on
TV

FLATN.......Re-grid multiple fields into one image incl sensitivity
COORDINA selects the output central coordinate.
PBCOR.......Task to apply or correct an image for a primary beam.
COORDINA provides the pointing center if necessary
SDVEL.......Shifts spectral-line single-dish data to a given
velocity.  COORDINA provides the coordinate to be used
for the velocity reference.
SPCOR.......Task to correct an image for a primary beam and spectral
index.  COORDINA provides the pointing center if
necessary.
SUFIX.......Modifies source numbers on uv data.  COORDINA provides
the coordinates of a new source.
```

AIPS