Appendix B: Global Variables

Global variables are referenced by LAS application modules to help determine processing options. These global variables allow the user greater control of the processing. The user has access to two different sets of global variables, one for TAE and one for LAS. Some of these global variables should only be modified by the system manager. The LAS module dspglob can be used to view the current value of each global. By convention, all LAS/TAE global variable names begin with the dollar sign ("$").

Global variables may be set using the let command in the form let global-name = new-value . For example,

  LAS74> LET $MSGTIM = 10 

  LAS74> let $prompt = "NEXT" 

The descriptions of the global variables available under LAS are in different locations. Descriptions of LAS global variables may be obtained during an interactive LAS session by typing tutor lasgbls and then help global-name. Similarly, information is available about TAE global variables by tutoring on the taegbl command. Additional information about TAE global variables is provided in the TAE Command Language (TCL) User's Manual.

The most commonly used or modified global variables are:

$COMPFLG

Specifies whether image files should be compressed whenever a LAS function is run.

$CPASSO

Specifies whether associated files (other than the history file, .his) should be copied whenever a LAS function is run.

$DELFLG

Specifies whether or not the output files being created by the application program are deleted by the application when a fatal error is encountered.

$DDRVFLG

Specifies whether fields of the DDR which are not known by the application program should be flagged as INVALID or UNKNOWN.

$FNAME

Defines the facility name to be used in the standard heading for printed reports.

$FADDR

Defines the facility address to be used in the standard heading for printed reports.

$HISTRY

Specifies whether or not the user wants history records copied from input images to output images. Options are

"NO"

Do not copy the history records. Only the history record for the current module is written to the output image's history file.

"YES"

Do copy the history records. The history records from the input image(s)are copied to the beginning of the output image's history file.

$LASTCMD

Contains the 20 commands most recently entered at the LAS74 prompt. Can also be viewed by repeatedly pressing the up-arrow key.

$LOG

The name of current session log, usually session.tsl.

$MINMAX

Defines whether or not the minimum and maximum pixel values should be computed for each band of the output image(s).

$MSGTIM

The number of wall clock seconds between processing progress messages, which typically report the current image line and/or band being processed.

$PRINTER

The name of the printer to receive formatted output when the user enters LP as a value for the PRINT parameter of an LAS module.

$PROJTOL

The projection tolerance (in pixels) for comparing the corner coordinates of two or more input images. If the difference between the corner coordinates of two image windows does not exceed this value, the windows are considered to be equal.

$PROMPT

The character string to be displayed before the ">" of the TAE/LAS command mode prompt. It can be a maximum of fifteen characters.

$TUTOR

The display mode to be used by tutor, either screen or noscreen.

$USERLIB

The library containing user-written procedures. The default is the user's current working directory.