### 13 Interaction Mode

We have seen the different co-ordinate systems Kappa uses. Now we address how the applications obtain co-ordinate information itself. Applications often permit a variety of mechanisms for obtaining those co-ordinates. Typical possibilities are as follows.

Catalogue
— In this mode the application reads a file containing a positions list. This can either be a FITS binary table, or a text file in STLformat, and can contain WCS information allowing positions within the catalogue to be aligned with other data. Positions lists can be created by several applications such as CURSOR, LISTMAKE, CENTROID, etc.
Cursor
— This mode utilises the cursor of the current graphics device. For this to work the array must already be displayed as an image, or a contour plot, or line plot (provided the application handles one-dimensional data), and the picture is stored in the graphics database.
Interface
— This mode obtains co-ordinates from the parameter system, usually in response to prompting.
File
— In this mode the application reads a text file containing a list of co-ordinates in free format, one object per record. There may be commentary lines in the file beginning with # or !. The format and syntax of the files are ad hoc, and are described in the application documentation.

Applications that permit these options have a parameter, called MODE, by which you can control how positional data are to be acquired. It would be tedious to have to specify a mode for each application, therefore Kappa has a global parameter—the interaction mode—to which each application’s interaction-mode parameter is defaulted. The global value remains in force until you change it by assigning an application’s interaction mode on the command line. The following examples shows the effect of the global parameter. For compactness GLOBALS will merely show the interaction mode.

First we display an image on the xw windows device.

ICL> gdset xw
ICL> display $KAPPA_DIR/ccdframec mode=pe \ Data will be scaled from 2366.001 to 2614.864. ICL> globals The current interaction mode is : <undefined> Now we obtain the centroids of a couple of stellar/galaxian images via each of the interaction modes. First in cursor mode. Note that CENTROID obtains the name of the input NDF from the graphics database in this mode. If you need to preview which NDF is going to be selected use the PICIN command. ICL> centroid mode=c Current picture has name: DATA, comment: KAPPA_DISPLAY. Using /star/bin/kappa/ccdframec as the input NDF. To select a point press the left button on the mouse or trackerball. To exit press the right button. Use the cursor to select one point. Input guess position was 86.23534, 295.0848 Output centroid position is 86.41057, 295.1141 Use the cursor to select one point. Input guess position was 73.32529, 318.9757 Output centroid position is 72.76437, 318.9484 Use the cursor to select one point. If we look at the global parameters again, indeed we see that it has become cursor mode. Now we’ll see the effect of changing the mode parameter. Note that unless it is undefined or the application does not support the current mode, you must change the mode on the command line. First we shall prompt for the co-ordinates. A null ends the loop. ICL> centroid mode=i NDF - Array to be analysed /@/star/bin/kappa/ccdframec/ > INIT - Guess at co-ordinates of star-like feature /108.8,403.5/ > 86,295 Input guess position was 86, 295 Output centroid position is 86.41057, 295.1141 INIT - Guess at co-ordinates of star-like feature /86,295/ > 73.3,319 Input guess position was 73.3, 319 Output centroid position is 72.76437, 318.9484 INIT - Guess at co-ordinates of star-like feature /73.3,319/ > ! Finally, we can create a text file called starlist.dat and run CENTROID in file mode. ICL> cat > starlist.dat 86 295 73 320 CTRL/D ICL> centroid mode=f COIN - File of initial positions /@centroid.lis/ > starlist.dat NDF - Array to be analysed /@$KAPPA_DIR/ccdframec/ >

Input guess position was     86, 295
Output centroid position is  86.41057, 295.1141

Input guess position was     73, 320
Output centroid position is  72.76437, 318.9484

Such co-ordinate files can also be created interactively with images by CURSOR.