Displaying contour maps

CONTOUR-MAP	Plot of average or integrated intensity in given range
GREYSCALE-MAP	As for CONTOUR-MAP, but greyscale and/or contours.
ROTATE-MAP	Regrid cube to new set of spatial axes
SET-CONTOUR-LEVELS	Set contour levels for CONTOUR, P-L-P and CHANN-MAP
SET-GREYSCALE	Set greyscaling for GREYSCALE, P-L-P and CHANN-MAP
SET-MAP-SCALES	Set the map window and axes
SET-MAP-SIZE	Set the physical size of the map output
SET-MAP-PARAMETERS	Set up things like contour line type
SET-MAP-ACCEPT	Define acceptance criteria for ADD-TO-MAP
WRITE-ASCII-MAP	Write map values/positions to ascii file (MONGO etc)
WRITE-FITS-MAP	Write map to 2-D FITS file suitable for AIPS
WRITE-GILDAS-IMAGE	Write current map to a ``bare-bones'' GILDAS cube

Greyscale or contour plots may be made for any two co-ordinates (R.A., Dec. and Velocity), with either integation or averaging over a specified range in the remaining co-ordinate. The contours or greyscale are only printed where the data exist in the input map. For contours, this requires that for a given `cell' on the contour plot there must be valid data values at all four vertices. If this condition is not met no contours are plotted in the cell. I think this is better than using zeros to fill-in for missing data, as this may lead to a spurious boundary to the source.

Map spatial coordinates can be presented in either relative form, as offsets in arcseconds from the map centre, or in absolute form (the latter only if the map axis is aligned with the equatorial (R.A./Dec.) coordinate system). To produce a contour map use the command CONTOUR-MAP (Figure 3.4); to produce a greyscale map (with or without overlaid contours) use the command GREYSCALE-MAP. Where possible, a scale-bar is presented either above or to the right of a grey-scaled plot -- where ever there is most room. SET-MAP-PARAMETERS can be used to suppress the header information if so required.

It is first necessary for the program to create a binary image of the particular slice of the cube you require. The image is stored in a (temporary) file ``mapplane.tmp", and the last version of this is retained after a plot is made. So if you protect this file by renaming it to something else, it can be used directly as input to the MONGO IMAGE command for more fancy plotting. SET-MAP-SCALES should be used both to choose which co-ordinates are plotted, and to set the scales for x and y co-ordinates and binning in the z-coordinate. Cuts in arbitrary spatial directions can made by defining a non-zero rotation angle in ROTATE-MAP.

The map size (in mm) must have been defined using SET-MAP-SIZE -- use $0 \times 0$ to use the entire available plot area. The contouring is set using SET-CONTOUR, which allows automatic contouring if so desired. You can set parameters to control whether the sample points are indicated on the map, the level of interpolation applied to the raw map and the line types to use for various contours, by using SET-MAP-PARAMETERS.

The 2-D graphics associated with GREYSCALE and CONTOUR-MAP (and to a lesser extent PLOT-LINE PARAMETERS and CHANNEL-MAPS) are very similar in the use of the cursor to those that apply to 1-D plotting. Possible menu items are given below -- not all are available for all commands:

Key	Mnemonic	Function
H	HELP	Produces a list of all valid options
C	CLEAR	Erase the alpha (ASCII) screen
L	LEFT	Define the left-hand boundary of the current `box'
R	RIGHT	Define the right-hand boundary of the current box
T	TOP	Define the top boundary of the current box
B	BOTTOM	Define the bottom boundary of the current box
D	DRAW	Draw the current box
N	NEWLIM	Redraw the plot taking the current box as new limits. Note that if the limits have not been redefined in one co-ordinate then you get back the original limits according to SET-MAP-SCALES
I	CONTOUR	Lets you adjust the contouring ``interactively"
W	NEWGREY	Lets you adjust the greyscaling ``interactively"
1	ONE	Switch to colour table 1 - linear black to white
2	TWO	Switch to colour table 2 - colour contours
3	THREE	Switch to colour table 3 - power-law black to white
4	FOUR	Switch to colour table 4 - blue to yellow
5	FIVE	Switch to colour table 5 - MRAO colour spiral
0	ZERO	Toggle logarithmic/linear greyscaling
X	MAXMIN	Tells you the maximum and minimum on MAPPLANE.TMP
S	INTEG	Reports the integrated intensity inside LRTB box.
M	MARKZ	Make triangle and write map value at crosshair position
G	GETSPEC	Grab spectrum from current map position and place in stack X position.
V	VALID	Make spots at positions for which there is valid data in the cube.
?	TELLZ	Write (x,y) position and map value to alpha screen.
Q	QUIT	Leave interactive graphics
E	END	Leave interactive graphics, erase graphics screen

These options may be used to label contour values and peaks, to modify the plot window, and most importantly, in conjunction with ADD-TO-MAP, to modify and replace spectra without ever having to worry about typing in or even working out positions. Just position the cursor at the position with suspect data, type G and then exit the map. Now work on the spectrum, which is tagged with the correct position, and when you are happy with it, type ADD-TO-MAP, and it will replace the old version. Iterate until the map suits you and then quit.

Two commands have been provided to help you export maps to other formats. WRITE-ASCII-MAP produces an ascii listing of the value of the current map, together with X and Y offsets from the map center. This may be read into programs such as MONGO as a simple 2-D image. There is also the command WRITE-GILDAS-IMAGE , which produces a very simple GILDAS data cube (``image''). The header details are blank, and have to be filled in with the GILDAS HEADER command; it may also be necessary to use the GILDAS TRANSPOSE command to generate the required x-y-v axis order from the output v-x-y cube.