AIPS HELP file for CNTR in 31DEC21
As of Tue Jul 27 14:52:28 2021
CNTR: Task to generate a contour plot as TV image or plot file
USERID -32000.0 32000.0 User ID. ignored
INNAME Image name(name).
INCLASS Image name(class).
INSEQ 0.0 9999.0 Image name(seq. #). 0=>high
INDISK Disk drive #. 0=>any
BLC 0.0 4096.0 Bottom left corner of image
TRC 0.0 4096.0 Top right corner of image
XYRATIO 0.0 10.0 X to Y axis plot ratio. 0=>
header inc or window ratio
LTYPE -410.0 410.0 Type of labeling: 1 border,
2 no ticks, 3 standard, 4 rel
to center, 5 rel to subim cen
6 pixels, 7-10 as 3-6 with
only tick labels
<0 -> no date/time
PLEV -99.0 100.0 Percent of peak for levs.
CLEV Absolute value for levs
(used only if PLEV = 0).
LEVS -9999.0 99999.0 Contour levels (up to 30).
DOCIRCLE -1.0 1.0 > 0 => extend ticks to form
STVERS -1.0 46655.0 STar file version number.
STFACTOR -9999.0 9999.0 Scale star sizes: 0 => none.
> 0 crosses with no labels
< 0 crosses with labels
DOTV -1.0 1.0 > 0 Do plot on the TV, else
make a plot file
GRCHAN 0.0 8.0 Graphics channel 0 => 1.
TVCORN 0.0 2048.0 TV pixel location of bottom
left corner of image 0=> self
scale, non 0 => pixel scale.
Use: CNTR will write commands to a plot file for the execution
of a contour plot for an image. CNTR supports TELL
operations QUIT and ABOR only.
USERID......The ID of the owner of the image. Ignored.
INNAME......Image name (name). Standard defaults.
INCLASS.....Image name (class). Standard defaults.
INSEQ.......Image name (seq. #). 0 => highest.
INDISK......Disk unit #. 0 => any.
BLC.........Bottom Left Corner of image to contour.
(0,0) means (1,1).
TRC.........Top Right Corner of image to contour.
(0,0) means top right corner of map.
XYRATIO.....The ratio of the X-axis to Y-axis pixel
separations. 0 => X to Y inc. in map header
if related, else Y to X window
LTYPE.......Labelling type, see HELP LTYPE for details:
1 = border, 2 = no ticks, 3 or 7 = standard, 4 or 8 =
relative to ref. pixel, 5 or 9 = relative to subimage
(BLC, TRC) center, 6 or 10 = pixels. 7-10 all labels
other than tick numbers and axis type are omitted.
Less than 0 is the same except that the plot file
version number and create time are omitted.
Add n * 100 to alter the metric scaling.
PLEV........Percent of peak for the contour increment. If
PLEV and CLEV are zero, 10 is used.
CLEV........Image intensity value for the contour increment.
Used only if PLEV = 0.
LEVS........Contour levels in units of the increment. The
levels must be in ascending order and a maximum
of 30 levels are permitted. 0 => -10,-9,
DOCIRCLE....False (<= 0) means that tick marks are short lines
extending inward from the plot borders. True (>0)
requests that a full coordinate grid be drawn.
STVERS......Version number of ST (star position) file to be
used to plot star positions as plus signs.
0 => highest, < 0 => no star positions plotted
STFACTOR....Scale factor used to multiply star sizes in file
for plotting. > 0 => scale star size
= 0 => don't plot stars.
< 0 => scale by abs(STFACTOR) and
show any star label
DOTV........> 0 => plot directly on the TV device, otherwise
make a plot file for later display on one or
more devices (including the TV if desired).
GRCHAN......Graphics channel (1 - 7) to use for line drawing.
0 => use multiple graphics planes for the various parts
of the graphical drawing.
TVCORN......TV pixel location (X,Y) where the bottom left-
corner of the plot is to be placed. If either is
zero, use the largest possible self scaling, else
use pixel scaling with specified origin on the TV.
CNTR: Task to create a contour-plot extension file for an image
RELATED PROGRAMS: PCNTR, KNTR, LWPLA, TKPL, TVPL, TVWIN
CNTR generates a plot extension file containing an
intensity contour plot, its border, and labels. The window
limits and contour levels are recorded in the header of the plot
file, and may be listed on your terminal with EXTLIST. CNTR
indicates positive and negative contour values by continuous and
broken lines, respectively.
The plot itself may be displayed on a printer, TEK screen,
or TV graphics channel by the tasks LWPLA, TKPL, or TVPL
Contour plots are often more useful for quantitative image
analysis than gray-scale or profile plots, and most maps are
published in the form of contour plots. By suitable choice of
contour levels, a contour plot can give a quantitative display
of all features in an image with very large dynamic range. The
contour plot of a map will be messy if contours are plotted at
levels below about 3 times the rms noise.
Contour plots tend to emphasize gradients in intensity. The
contour plot of a complex image, especially one with local
minima, can therefore be confusing. Note that a local (but
non-negative) minimum will be indicated by a closed continuous
contour, so that it is indistinguishable from a maximum. Also,
the simple interpolation routine used by CNTR may produce jagged
"staircase" contours. This problem can be minimized by
interpolating the image with the task GEOM.
A convenient way to select the plot corners is to display
the image on the TV and set the rectangular boundary of the
subimage to be plotted with the verb TVWIN.
Nonzero elements LEVS(I) in this 30-element vector
specify the contour levels LEVS(I)*PLEV or LEVS(I)*CLEV to be
plotted. They must be specified in increasing order and lie
within the range -9999.0 to +99999.0. It is easy to specify a
large number of LEVS values with a FOR loop. For example,
FOR I=1 TO 20;LEVS(I)=2**((I-1)/2.);END ; LEVS(21)=0.
yields successive contours separated by factors of 2**.5
If you request more than one negative level via a statement
of the form
LEVS = a , b , c , d , e , f , g
you must use commas between the negative levels. Otherwise, the
minus sign(s) will be treated as subtraction symbols by POPS and
the desired levels will be combined into a single negative
1=> unlabeled rectangular border
2=> rectangular border plus labels (image name, center
position, etc.). Beware that the PEAK FLUX label
gives the peak flux in the whole image, not that in
the subimage plotted.
3=> rectangular border, labels, and border tick marks
indicating absolute coordinates (r.a., decl., etc.)
4=> rectangular border, labels, and border tick marks
indicating coordinates relative to the coordinates
of the image reference pixel
5=> rectangular border, labels, and border tick marks
indicating coordinates relative to the center of
the subimage plotted
6=> rectangular border, labels, and border tick marks
indicating image pixel numbers
7-10 => like 3-6 but the extra labels are omitted.
An LTYPE which is < 0 is used, in absolute value, to
control the labeling as listed above and specifies that
the "PLOT FILE VERSION n CREATED date time" string is
not placed on the plot.
XYRATIO can be used to change the plot aspect ratio.
Values >1 stretch the X-axis, values <1 compress it.
DISPLAYING THE PLOT:
On termination of CNTR, the messiness of the plot can be
judged by looking at the message on your monitor:
GFINIS: NUMBER OF RECORDS GUESSED NNN USED MMM
If MMM is much greater than 200, the plot will be complicated.
If this happens when you thought you were contouring a simple
small field, you have probably set the levels too low (or have
specified the contouring window incorrectly). You may wish to
check your inputs before trying to display the plot. It is
always worth using TKPL or TVPL to preview a new plot before
routing it to the slower LWPLA, unless you are very sure that
your input parameters were well chosen.
You can use STarFACTOR to add crosses or other symbols to
your plot to denote the postions of stars or other objects.
First you must read the postions into a ST table using STARS.
Then set INVER to the table version number. You can scale the
sizes of the crosses be setting STFACTOR > 0. Set STFACTOR to
1.0 for no scaling (use the star sizes in the ST table). You
can label the crosses with a character string to help identify
them by setting STFACTOR < 0. The label is the text string
entered when creating the ST table. The star sizes in this case
will be scaled by ABS(STFACTOR). Note that you can also rotate
the crosses through an angle by specifying a positon angle when
you create the ST table in STARS (see STARS for more