SLOPE AND ASPECT GENERATION FROM A DTM

MODULE SLOPES

Slope and Aspect Calculation

Issue 7.0 13-March-1989
Copyright (C) 1989  Laser-Scan Ltd
Science Park, Milton Road, Cambridge, England CB4 4FY  tel: (0223) 420414

Document "SLOPES Reference"                     Category "Reference"
Document Issue 7.0      M W S Reid              13-March-1989
         Issue 6.0      D R Catlow              08-September-1988
         Issue 5.0      D R Catlow              25-January -1988
         Issue 4.0      D R Catlow              17-October -1986
         Issue 3.0      D R Catlow              24-February-1986



--------------------------------------------------------------------------------
MODULE SLOPES

--------------------------------------------------------------------------------

FUNCTION

--------------------------------------------------------------------------------

FORMAT

--------------------------------------------------------------------------------

PROMPTS

--------------------------------------------------------------------------------

--------------------------------------------------------------------------------

DESCRIPTION

--------------------------------------------------------------------------------

SLOPE AND ASPECT CALCULATION

--------------------------------------------------------------------------------

SHADE CALCULATION

--------------------------------------------------------------------------------

HEIGHT DIFFERENCE CALCULATION

--------------------------------------------------------------------------------

OUTPUT MAP PARAMETERS

--------------------------------------------------------------------------------

DTI FILE OUTPUT AND GRAPHICS DISPLAY

--------------------------------------------------------------------------------

DISPLAY ANNOTATION

--------------------------------------------------------------------------------

USE OF A DIGITISING TABLE, TABLE PUCK AND MENU

--------------------------------------------------------------------------------

SLOPES COMMANDS

COMMAND LIST

The following commands are defined :


        @               !               ANGLE_INTERVAL  ASPECT  
        CENTRE          CLEAR           CLEAR LABELS    COLOUR  
        DATA_TYPE       DEFAULT ASPECT  DEFAULT HEIGHT_DIFFERENCE       
        DEFAULT SHADE   DEFAULT SLOPE   DISABLE ABSOLUTE
        DISABLE AVERAGE DISABLE CLASSIFY                DISABLE CLEAR
        DISABLE GRAPHICS                DISABLE GREYSCALE
        DISABLE LEGEND  DISABLE NULL_BORDER             DISABLE PERCENT 
        DISABLE RECENTRE                DISABLE TABLE   DISABLE TEXT   
        DRAW LABEL      ENABLE ABSOLUTE
        ENABLE AVERAGE  ENABLE CLASSIFY ENABLE CLEAR    ENABLE GRAPHICS    
        ENABLE GREYSCALE                ENABLE LEGEND   ENABLE NULL_BORDER
        ENABLE PERCENT  ENABLE RECENTRE ENABLE TABLE    ENABLE TEXT   
        ENLARGE         EXIT            FILEIN          FILEOUT
        HEIGHT_DIFFERENCE               HELP            LABEL POSITION
        LABEL SIZE      LEGEND POSITION LUT             REDUCE
        REFLECTANCE_MAP SETUP MAP       SETUP MENU      SHADE
        SHOW ANNOTATION SHOW ASPECT     SHOW ENABLE     SHOW FILES
        SHOW HEIGHT_DIFFERENCE          SHOW SHADE      SHOW SLOPE
        SLOPES          SPAWN           STEP            SUN_ANGLE
        SUN_POSITION    UNITS           VALUE_RANGE     WAIT
        WINDOW          ZLIMITS         ZSCALE
        
        

_@ COMMAND

--------------------------------------------------------------------------------
_@

--------------------------------------------------------------------------------
FORMAT: _@ file-spec

--------------------------------------------------------------------------------
Command parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

SLOPES offers the facility of command input from an indirect command file. The '@' character preceding a file-spec will cause SLOPES to open and read commands from the specified file until:

Nested command files are not supported (i_.e_. a command file containing an '@' command), although sequential '@' commands are supported when read from SYS$COMMAND.

As an aid to batch log interpretation SLOPES will echo all commands read from an indirect command file.

--------------------------------------------------------------------------------
Messages:

The following messages are specific to the _@ command:


*** ERROR *** Specifying command @
Command file specification is missing

*** ERROR *** Specifying command @
Unable to open indirect command file 'file-spec'

*** ERROR *** Specifying command @
Nested command files not supported

--------------------------------------------------------------------------------
Examples:


SLOPES> @SLOPES_TEST
SLOPES> STEP 7
SLOPES> VALUE_RANGE 10 20
SLOPES>

_! COMMAND

--------------------------------------------------------------------------------
_!

--------------------------------------------------------------------------------
FORMAT: _! [comment text]

--------------------------------------------------------------------------------
Command parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

An exclamation mark is the standard TVES package comment delimiter. All text (and numbers) which lie to the right of a '!' character are excluded from command interpretation. Comments are useful for annotating command procedures used in batch processing etc.

--------------------------------------------------------------------------------
Messages: None.

--------------------------------------------------------------------------------
Examples:


SLOPES> ENABLE AVERAGE !calculate average height differences<CR>
SLOPES> ENABLE ABSOLUTE !use absolute coordinates<CR>
SLOPES>

ANGLE_INTERVAL COMMAND

--------------------------------------------------------------------------------
ANGLE_INTERVAL

--------------------------------------------------------------------------------

FORMAT:         ANGLE_INTERVAL   angular_interval

--------------------------------------------------------------------------------
Command parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

ANGLE_INTERVAL is used to define the angular step value for ASPECT calculation. If output to a graphics device has been selected with the ENABLE GRAPHICS command then each angular step is displayed in a different colour.

If output is to a DTI file then if the ENABLE CLASSIFY command has been given, each classified index is output to the DTI file. eg. if an angular step of 10 degrees is specified then aspect values of 1 to 10 degrees would be output to the DTI file with a value of 1, 11 to 20 degrees with a value of 2 etc.

If the ENABLE CLASSIFY command is not specified then the ANGLE_INTERVAL command has no effect on the output to a DTI file.

--------------------------------------------------------------------------------
Messages:

The following error messages are specific to the ANGLE_INTERVAL command.


*** ERROR *** Specifying command ANGLE_INTERVAL
Command requires an integer value between 3 and 360

--------------------------------------------------------------------------------
Examples:

SLOPES>ANGLE_INTERVAL 20
SLOPES>

ASPECT COMMAND

--------------------------------------------------------------------------------
ASPECT

--------------------------------------------------------------------------------

FORMAT:         ASPECT

--------------------------------------------------------------------------------
Command parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

This command calculates an ASPECT map indicating the direction of SLOPE at each node in the DTM. Aspect is measured in degrees clockwise from north (ie east = 90 degrees, west = 270 degrees).

Further information on the ASPECT algorithm used is given in the Description section.

The aspect information is either displayed on the graphics screen, if the ENABLE GRAPHICS command has been given and/or to a DTI file if the FILEOUT command has been issued.

If output to a graphics device is selected then either a grey or colour image is produced depending on whether the ENABLE GREY command has been given. By default a colour image is produced. The displayed step intervals are controlled by the ANGLE_INTERVAL command.

If output is to a DTI file then if the ENABLE CLASSIFY has been given each classified index, as defined by the ANGLE_INTERVAL command is output to the DTI file. For example, if an angular step of 10 degrees is specified then aspect values of 1 to 10 degrees are output to the DTI file with a value of 1, 11 to 20 degrees with a value of 2 etc. Otherwise the actual calculated aspect values are output.

ASPECT information is only calculated for matrix nodes lying within the currently defined WINDOW.

Typing (Pressing the Ctrl and C keys together) aborts the calculation and display of ASPECT.

--------------------------------------------------------------------------------
Messages:

The following error messages are specific to the ASPECT command.


*** ERROR *** Specifying command ASPECT 
Output medium not specified
Use ENABLE GRAPHICS or FILEOUT commands

*** ERROR *** Specifying command ASPECT 
No input DTI file had been specified

*** ERROR *** Specifying command ASPECT 
DATA_TYPE BYTE illegal for ASPECT output

--------------------------------------------------------------------------------
Examples:

SLOPES>ASPECT
SLOPES>

CENTRE COMMAND

--------------------------------------------------------------------------------
CENTRE

--------------------------------------------------------------------------------

FORMAT:         CENTRE x_coord y_coord

--------------------------------------------------------------------------------
Command parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

The displayed image is centred around the screen position corresponding to the supplied matrix x y coordinate point provided they lie within the geographical bounds of the file.

This command has effect only on a graphics device which supports hardware pixel replication.

--------------------------------------------------------------------------------
Messages:

The following error messages are specific to the CENTRE command.


*** ERROR *** Specifying command CENTRE
A graphics device is not selected

*** ERROR *** Specifying command CENTRE
Command requires 1 DTI x,y coord pair

--------------------------------------------------------------------------------
Examples:

SLOPES>CENTRE 100 100
SLOPES>

CLEAR

--------------------------------------------------------------------------------
CLEAR

--------------------------------------------------------------------------------

FORMAT:         CLEAR 

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

This command, when issued with no qualifiers, clears the entire screen of displayed information.

--------------------------------------------------------------------------------
Messages:


The following messages are specific to the CLEAR command.

*** ERROR *** specifying command CLEAR
Valid qualifier is LABEL

--------------------------------------------------------------------------------
Example:

SLOPES>CLEAR
SLOPES>

CLEAR LABEL

--------------------------------------------------------------------------------
CLEAR LABEL

--------------------------------------------------------------------------------

FORMAT:         CLEAR LABEL

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

User annotation which has been specified with the DRAW LABEL command is cleared from the screen. Any underlying image is preserved.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the CLEAR command.


*** ERROR *** specifying command CLEAR
Valid qualifier is LABEL

--------------------------------------------------------------------------------
Example:

SLOPES>CLEAR LABEL
SLOPES>

COLOURS COMMAND

--------------------------------------------------------------------------------
COLOURS

--------------------------------------------------------------------------------

FORMAT:         COLOURS I1 I2 ...I7

--------------------------------------------------------------------------------
Command parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

The COLOUR command allows the colour indices associated with step values to be reassigned.

eg. 
        COLOURS 3 12 7

allocates colours 3,12 and 7 in the colour table to the first three gradient steps in a slope map.

The command applies only to SLOPE and HEIGHT_DIFFERENCE maps. If the ENABLE CLASSIFY command has been given, then the colour index values are output to the DTI file.

--------------------------------------------------------------------------------
Messages:

The following error messages are specific to the COLOURS command.


*** ERROR *** Specifying command COLOURS
Command requires between 1 and 7 colour index values

*** ERROR *** Specifying command COLOURS
Colour values should be in the range 1 to 127

--------------------------------------------------------------------------------
Examples:

SLOPES>COLOURS 2 5 20
SLOPES>

DATA_TYPE

--------------------------------------------------------------------------------
DATA_TYPE

--------------------------------------------------------------------------------

FORMAT:         DATA_TYPE keyword

--------------------------------------------------------------------------------
Command Parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

The DATA_TYPE command is used to set the data type of the output DTI file specified using the FILEOUT command.

Note that ASPECT maps may not be output if BYTE data type has been selected, unless ENABLE CLASSIFY has been specified.

The default data type is WORD.

--------------------------------------------------------------------------------
Messages:_None
The following message is specific to the DATA_TYPE command.


*** ERROR *** specifying command DATA_TYPE
Valid qualifier is BYTE, LONGWORD, REAL or WORD.

--------------------------------------------------------------------------------
Example:

SLOPES>DATA_TYPE WORD
SLOPES>

DEFAULT ASPECT

--------------------------------------------------------------------------------
DEFAULT ASPECT

--------------------------------------------------------------------------------

FORMAT:         DEFAULT ASPECT

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

This command resets the default program parameters for the calculation and display of aspect maps. The following values are set: -


            ANGLE_INTERVAL          30 degrees
            ZLIMITS                 DTI file minimum and maximum values
            LUT ASPECT              LSL$LOOKUP:SLOPES.DAT
            Colour Image Selected

--------------------------------------------------------------------------------
Messages:


The following message is specific to the DEFAULT command.


*** ERROR *** specifying command DEFAULT
Valid qualifier is SLOPE ,ASPECT, SHADE or HEIGHT_DIFFERENCE

--------------------------------------------------------------------------------
Example:

SLOPES>DEFAULT ASPECT
SLOPES>

DEFAULT HEIGHT_DIFFERENCE

--------------------------------------------------------------------------------
DEFAULT HEIGHT_DIFFERENCE

--------------------------------------------------------------------------------

FORMAT:         DEFAULT HEIGHT_DIFFERENCE

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

This command resets the default program parameters for the calculation and display of height difference maps. The following values are set: -


            STEP                    5 
            VALUE_RANGE             0 - 60 
            ZLIMITS                 DTI file minimum and maximum values
            LUT HEIGHT__DIFFERENCE  LSL$LOOKUP:SLOPES.DAT
            Calculation of Average Height difference selected

--------------------------------------------------------------------------------
Messages:


The following message is specific to the DEFAULT command.


*** ERROR *** specifying command DEFAULT
Valid qualifier is SLOPE ,ASPECT, SHADE or HEIGHT_DIFFERENCE

--------------------------------------------------------------------------------
Example:

SLOPES>DEFAULT HEIGHT_DIFFERENCE
SLOPES>

DEFAULT SHADE

--------------------------------------------------------------------------------
DEFAULT SHADE

--------------------------------------------------------------------------------

FORMAT:         DEFAULT SHADE

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

This command resets the default program parameters for the calculation and display of shaded maps. The following values are set: -


            SUN_ANGLE               45 degrees
            SUN_POSITION            315 degrees (North-West)
            REFLECTANCE_MAP          2
            LUT SHADE               LSL$LOOKUP:GREY.DAT

--------------------------------------------------------------------------------
Messages:


The following message is specific to the DEFAULT command.


*** ERROR *** specifying command DEFAULT
Valid qualifier is SLOPE ,ASPECT, SHADE or HEIGHT_DIFFERENCE

--------------------------------------------------------------------------------
Example:

SLOPES>DEFAULT SHADE
SLOPES>

DEFAULT SLOPE

--------------------------------------------------------------------------------
DEFAULT SLOPE

--------------------------------------------------------------------------------

FORMAT:         DEFAULT SLOPE

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

This command resets the default program parameters for the calculation and display of slope maps. The following values are set: -


            STEP                    5 degrees
            VALUE_RANGE             0 - 60 degrees
            ZLIMITS                 DTI file minimum and maximum values
            LUT SLOPE               LSL$LOOKUP:SLOPES.DAT
            Slope data in degrees

--------------------------------------------------------------------------------
Messages:


The following message is specific to the DEFAULT command.


*** ERROR *** specifying command DEFAULT
Valid qualifier is SLOPE ,ASPECT, SHADE or HEIGHT_DIFFERENCE

--------------------------------------------------------------------------------
Example:

SLOPES>DEFAULT SLOPE
SLOPES>

DISABLE ABSOLUTE

--------------------------------------------------------------------------------
DISABLE ABSOLUTE

--------------------------------------------------------------------------------

FORMAT:         DISABLE ABSOLUTE

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

DISABLE ABSOLUTE cancels a previous ENABLE ABSOLUTE command. If DISABLE ABSOLUTE is given, then coordinate values required by the WINDOW command, supplied in metre or projection units, must be specified as an offset from the SW corner of the matrix.
By default window values should be specified as absolute coordinates.

The SHOW ENABLE command may be used to check the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the DISABLE command.


*** ERROR *** Specifying command DISABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>DISABLE ABSOLUTE
SLOPES>

DISABLE AVERAGE

--------------------------------------------------------------------------------
DISABLE AVERAGE

--------------------------------------------------------------------------------

FORMAT:         DISABLE AVERAGE

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

DISABLE AVERAGE cancels a previous ENABLE AVERAGE command.
If DISABLE AVERAGE is given, then maximum height difference is calculated when the HEIGHT_DIFFERENCE command is given.

The SHOW ENABLE command may be used to check the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the DISABLE command.


*** ERROR *** Specifying command DISABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>DISABLE AVERAGE
SLOPES>

DISABLE CLASSIFY

--------------------------------------------------------------------------------
DISABLE CLASSIFY

--------------------------------------------------------------------------------

FORMAT:         DISABLE CLASSIFY

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

DISABLE CLASSIFY cancels a previous ENABLE CLASSIFY command. If DISABLE CLASSIFY is given, then the calculated SLOPE, HEIGHT_DIFFERENCE or ASPECT values are written to the output DTI file.

The SHOW ENABLE command may be used to check the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the DISABLE command.


*** ERROR *** Specifying command DISABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>DISABLE CLASSIFY
SLOPES>

DISABLE CLEAR

--------------------------------------------------------------------------------
DISABLE CLEAR

--------------------------------------------------------------------------------

FORMAT:         DISABLE CLEAR

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

DISABLE CLEAR cancels a previous ENABLE CLEAR command. If DISABLE CLEAR is given, then the screen is not automatically cleared before each new image is generated.

The DISABLE CLEAR command is useful to allow differences caused by changing output map parameters to be examined.

The SHOW ENABLE command may be used to check the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the DISABLE command.


*** ERROR *** Specifying command DISABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>DISABLE CLEAR
SLOPES>

DISABLE GRAPHICS

--------------------------------------------------------------------------------
DISABLE GRAPHICS

--------------------------------------------------------------------------------

FORMAT:         DISABLE GRAPHICS

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

DISABLE GRAPHICS cancels a previous ENABLE GRAPHICS command. If DISABLE GRAPHICS is given, then SLOPE, ASPECT, HEIGHT_DIFFERENCE or SHADE information is not output to the graphics device.

The SHOW ENABLE command may be used to check the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the DISABLE command.


*** ERROR *** Specifying command DISABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>DISABLE GRAPHICS
SLOPES>

DISABLE GREYSCALE

--------------------------------------------------------------------------------
DISABLE GREYSCALE

--------------------------------------------------------------------------------

FORMAT:         DISABLE GREYSCALE

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

DISABLE GREYSCALE cancels a previous ENABLE GREYSCALE command. The command is used in conjunction with the ASPECT command to specify that the aspect map should be displayed as a colour image.

The SHOW ENABLE command may be used to check the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the DISABLE command.


*** ERROR *** Specifying command DISABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>DISABLE GREYSCALE
SLOPES>

DISABLE LEGEND

--------------------------------------------------------------------------------
DISABLE LEGEND

--------------------------------------------------------------------------------

FORMAT:         DISABLE LEGEND

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

DISABLE LEGEND cancels a previous ENABLE LEGEND command. If DISABLE LEGEND is given, then no colour value guide is generated before an ASPECT, SLOPE, or HEIGHT_DIFFERENCE image is generated.

The SHOW ENABLE command may be used to check the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the DISABLE command.


*** ERROR *** Specifying command DISABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>DISABLE LEGEND
SLOPES>

DISABLE NULL_BORDER

--------------------------------------------------------------------------------
DISABLE NULL_BORDER

--------------------------------------------------------------------------------

FORMAT:         DISABLE NULL_BORDER

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

DISABLE NULL_BORDER cancels a previous ENABLE NULL_BORDER command. It disables null values being written to the first and last rows and columns in the output DTI file.

The DTM is conceptually expanded by 2 columns and 2 rows, and heights are interpolated linearly for the new points, to allow an output slope or aspect value to be calculated for the first and last column and row.

The SHOW ENABLE command may be used to check the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the DISABLE command.


*** ERROR *** Specifying command DISABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>DISABLE NULL_BORDER
SLOPES>

DISABLE PERCENT

--------------------------------------------------------------------------------
DISABLE PERCENT

--------------------------------------------------------------------------------

FORMAT:         DISABLE PERCENT

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

DISABLE PERCENT cancels a previous ENABLE PERCENT command. Gradient values are subsequently calculated in degrees of slope.

The SHOW ENABLE command may be used to check the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the DISABLE command.


*** ERROR *** Specifying command DISABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>DISABLE PERCENT
SLOPES>

DISABLE RECENTRE

--------------------------------------------------------------------------------
DISABLE RECENTRE

--------------------------------------------------------------------------------

FORMAT:         DISABLE RECENTRE

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

DISABLE RECENTRE cancels a previous ENABLE RECENTRE command.

The display remains at the current magnification factor, and is not recentred before the drawing of a new image.

To avoid undesirable effects it is advisable to DISABLE LEGEND and TEXT display when using DISABLE RECENTRE.

This command has effect only on a graphics device which supports hardware pixel replication. The SHOW ENABLE command may be used to check the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the DISABLE command.


*** ERROR *** Specifying command DISABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>DISABLE RECENTRE
SLOPES>

DISABLE TABLE

--------------------------------------------------------------------------------
DISABLE TABLE

--------------------------------------------------------------------------------

FORMAT:         DISABLE TABLE

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

The DISABLE TABLE command turns off input from the digitising table. Input from the table can be reselected using the ENABLE TABLE command.

The SHOW ENABLE command may be used to check on the status of table input.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the DISABLE command.


*** ERROR *** Specifying command DISABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>DISABLE TABLE
SLOPES>

DISABLE TEXT

--------------------------------------------------------------------------------
DISABLE TEXT

--------------------------------------------------------------------------------

FORMAT:         DISABLE TEXT

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

DISABLE TEXT disables the output of border information when an image is displayed. By default the DTI file name, area of interest, value range and current parameter settings are output to the screen.

The SHOW ENABLE command may be used to check the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the DISABLE command.


*** ERROR *** Specifying command DISABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>DISABLE TEXT
SLOPES>

DRAW LABEL

--------------------------------------------------------------------------------
DRAW LABEL

--------------------------------------------------------------------------------

FORMAT:         DRAW LABEL text

--------------------------------------------------------------------------------
Command parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

The specified text is written to the display.

By default the position of the text is along the bottom line of the current plotting area.

Both the size and position of the text may be changed by means of the LABEL SIZE and LABEL POSITION commands.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the DRAW LABEL command.


*** ERROR *** Specifying command DRAW
Command qualifier is LABEL

--------------------------------------------------------------------------------
Examples:

SLOPES> DRAW LABEL A Very Pretty Picture
SLOPES>

ENABLE ABSOLUTE

--------------------------------------------------------------------------------
ENABLE ABSOLUTE

--------------------------------------------------------------------------------

FORMAT:         ENABLE ABSOLUTE

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

If ENABLE ABSOLUTE is given, then coordinate values required by the WINDOW command, supplied in metre or projection units, must be specified as absolute (rather than relative) coordinate values.

For example if the projection indicates U.K. National Grid, then the WINDOW values may be specified as 6 figure National Grid coordinates.
By default window values should be specified as absolute coordinates.

This option can be disabled using the DISABLE ABSOLUTE command. The SHOW ENABLE command may be used to check the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the ENABLE command.


*** ERROR *** Specifying command ENABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>ENABLE ABSOLUTE
SLOPES>

ENABLE AVERAGE

--------------------------------------------------------------------------------
ENABLE AVERAGE

--------------------------------------------------------------------------------

FORMAT:         ENABLE AVERAGE

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

If the ENABLE AVERAGE command is given, then average height difference is calculated when a HEIGHT_DIFFERENCE map is generated. The SHOW ENABLE command may be used to check the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the ENABLE command.


*** ERROR *** Specifying command ENABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>ENABLE AVERAGE
SLOPES>

ENABLE CLASSIFY

--------------------------------------------------------------------------------
ENABLE CLASSIFY

--------------------------------------------------------------------------------

FORMAT:         ENABLE CLASSIFY

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

If ENABLE CLASSIFY is given, then SLOPE, HEIGHT_DIFFERENCE or ASPECT values are output as classified indices as defined by the STEP and COLOUR, or ANGLE_INTERVAL commands. The SHOW ENABLE command may be used to check the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the ENABLE command.


*** ERROR *** Specifying command ENABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>ENABLE CLASSIFY
SLOPES>FILEOUT TEST
SLOPES>STEP 10
SLOPES>COLOURS 5 10 15 20 30
SLOPES>SLOPE 1

File LSL$DTI:TEST.SLP opened for output


SLOPES>

ENABLE CLEAR

--------------------------------------------------------------------------------
ENABLE CLEAR

--------------------------------------------------------------------------------

FORMAT:         ENABLE CLEAR

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

If the ENABLE CLEAR command is given, then the graphics screen is automatically cleared prior to display of ASPECT, SLOPES, SHADE or HEIGHT_DIFFERENCE images. The SHOW ENABLE command may be used to check the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the ENABLE command.


*** ERROR *** Specifying command ENABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>ENABLE CLEAR
SLOPES>

ENABLE GRAPHICS

--------------------------------------------------------------------------------
ENABLE GRAPHICS

--------------------------------------------------------------------------------

FORMAT:         ENABLE GRAPHICS

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

The ENABLE GRAPHICS command initialises the graphics workstation. Subsequent SLOPES output generated by the SLOPE, ASPECT, HEIGHT_DIFFERENCE and SHADE commands is directed to the graphics display.

The SHOW ENABLE command may be used to check the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the ENABLE command.


*** ERROR *** Specifying command ENABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>ENABLE GRAPHICS
SLOPES>

ENABLE GREYSCALE

--------------------------------------------------------------------------------
ENABLE GREYSCALE

--------------------------------------------------------------------------------

FORMAT:         ENABLE GREYSCALE

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

The command is used in conjunction with the ASPECT command to specify that the aspect map should be displayed as a greyscale image.

The SHOW ENABLE command may be used to check the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the ENABLE command.


*** ERROR *** Specifying command ENABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>ENABLE GREYSCALE
SLOPES>

ENABLE LEGEND

--------------------------------------------------------------------------------
ENABLE LEGEND

--------------------------------------------------------------------------------

FORMAT:         ENABLE LEGEND

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

ENABLE LEGEND enables the display of a colour/value guide when an ASPECT, SLOPE or HEIGHT_DIFFERENCE command is given.

The position of the LEGEND on the screen may be changed with the LEGEND POSITION command.

The SHOW ENABLE command may be used to check the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the ENABLE command.


*** ERROR *** Specifying command ENABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:
SLOPES>ENABLE LEGEND
SLOPES>

ENABLE NULL_BORDER

--------------------------------------------------------------------------------
ENABLE NULL_BORDER

--------------------------------------------------------------------------------

FORMAT:         ENABLE NULL_BORDER

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

The ENABLE NULL_BORDER command specifies that null values are written to the first and last rows and columns in the output DTI file.

The null values output are dependent on the output data type specified with the DATA TYPE command. These values are specified in the DTILIB reference manual.

The SHOW ENABLE command may be used to check the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the ENABLE command.


*** ERROR *** Specifying command ENABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>ENABLE NULL_BORDER
SLOPES>

ENABLE PERCENT

--------------------------------------------------------------------------------
ENABLE PERCENT

--------------------------------------------------------------------------------

FORMAT:         ENABLE PERCENT

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

The ENABLE PERCENT command is used to select the calculation of percentage slope. Gradients for subsequent SLOPE commands are output as percentage slope. ie:-


                450 = 100%

Slopes of greater than 450 are output as 100%.

The SHOW ENABLE command may be used to check the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the ENABLE command.


*** ERROR *** Specifying command ENABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>ENABLE PERCENT
SLOPES>

ENABLE RECENTRE

--------------------------------------------------------------------------------
ENABLE RECENTRE

--------------------------------------------------------------------------------

FORMAT:         ENABLE RECENTRE

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

The ENABLE RECENTRE command specifies that the display is recentred and set to a magnification factor of one before the drawing of a new image.

This command has effect only on a graphics device which supports hardware pixel replication.

The SHOW ENABLE command may be used to check the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the ENABLE command.


*** ERROR *** Specifying command ENABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>ENABLE RECENTRE
SLOPES>

ENABLE TABLE

--------------------------------------------------------------------------------
ENABLE TABLE

--------------------------------------------------------------------------------

FORMAT:         ENABLE TABLE

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

The ENABLE TABLE command initialises the table monitor to allow input from a digitising table. The command SETUP MAP may be used to register a map to the DTI file. The SETUP MENU command allows commands to be issued using the SLOPES table menu. In the event of failure, input from the digitising table or puck button is not possible, and the program will accept commands only from the terminal.

Table initialisation will generally fail because no Table Monitor is currently active, or because the Table Monitor is locked by another user. If neither of these reasons appear to apply, you should consult the TABLIB Reference Manual, or seek guidance from your system manager.

If the logical name LSL$AUTO_ENABLE_TABLE is defined with a value of "1", then the table is initialised on program startup.

The DISABLE TABLE command may be used to turn off input from the digitising table.

The SHOW ENABLE command may be used to check on the status of table input.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the ENABLE command.


*** ERROR *** Specifying command ENABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>ENABLE TABLE
SLOPES>

ENABLE TEXT

--------------------------------------------------------------------------------
ENABLE TEXT

--------------------------------------------------------------------------------

FORMAT:         ENABLE TEXT

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

ENABLE TEXT enables the output of border information when an image is displayed. The DTI filename, area of interest, selected value range and current parameter settings are output to the screen.

The SHOW ENABLE command may be used to check on the status of the option.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the ENABLE command.


*** ERROR *** Specifying command ENABLE
Command qualifiers are ABSOLUTE, AVERAGE, CLEAR,
CLASSIFY, GRAPHICS, GREYSCALE, LEGEND, NULL_BORDER, PERCENT,
RECENTRE, TABLE or TEXT

--------------------------------------------------------------------------------
Examples:

SLOPES>ENABLE TEXT
SLOPES>

ENLARGE

--------------------------------------------------------------------------------
ENLARGE

--------------------------------------------------------------------------------

FORMAT:         ENLARGE

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

The screen image is magnified by a factor of 2 using pixel replication. If the command is repeatedly given the display will continue to be enlarged until the maximum magnification (x 16) is reached.

This command has effect only on a graphics device which supports hardware pixel replication.

--------------------------------------------------------------------------------
Messages

Display is at maximum magnification

--------------------------------------------------------------------------------
Examples:

SLOPES>ENLARGE
SLOPES>

EXIT

--------------------------------------------------------------------------------
EXIT

--------------------------------------------------------------------------------

FORMAT:         EXIT

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

The program is terminated, and any currently opened DTI files will be unmapped, along with any input or output IFF files.

(pressing the Ctrl and Z keys together) may also be used to exit from the program.

--------------------------------------------------------------------------------
Messages _None

--------------------------------------------------------------------------------
Example:

SLOPES>EXIT
_$

FILEIN

--------------------------------------------------------------------------------
FILEIN

--------------------------------------------------------------------------------

FORMAT:         FILEIN  file-spec

--------------------------------------------------------------------------------
Command parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

This command opens and maps into memory a DTI file.
Details derived from the header of the file are displayed on the terminal to confirm that the file has been successfully opened.

If the logical name LSL$MATRIX_DEFAULT_WINDOW is defined with a value of "1", then a default area of interest defined in matrix units of bottom left hand corner 1,1 and top right hand corner 200,200 is set when the file is opened. If the logical name is absent or has any other value, or if the input DTI file has fewer than 200 columns or 200 rows, then a default window equivalent to the total matrix is set.

The area of interest may be altered at any time by use of the WINDOW command.

If the rotation value (DTI_ORDER_CORNER) held in the header of the DTI file is not the default, (south west) then a warning message is output when the file is opened.

Information on the mapped DTI file may be obtained at any time by typing 'SHOW FILES'.

--------------------------------------------------------------------------------
Messages:


The following messages are specific to the FILEIN command.


*** ERROR *** Specifying command FILEIN
Filename is missing

--------------------------------------------------------------------------------
Example:

SLOPES>FILEIN TEST


File    :  LSL$DTI:TEST.DTI
Header  :  LSLA Data:  WORD

Units are DTI Matrix Value

Matrix Coverage   SW:     1      1  NE:   301   251
Matrix Window     SW:     1      1  NE:   301   251
Matrix Interval    E:     1          N:     1
Value Range         :     0    to    851
SLOPES>

FILEOUT COMMAND

--------------------------------------------------------------------------------
FILEOUT

--------------------------------------------------------------------------------
FORMAT: FILEOUT file-spec

--------------------------------------------------------------------------------
COMMAND PARAMETERS:

--------------------------------------------------------------------------------
DESCRIPTION:

The FILEOUT command specifies the name of the DTI file which is to receive the calculated SLOPE, ASPECT, HEIGHT_DIFFERENCE or SHADE data. The file is closed after calculations have taken place.

Note that output may take place both to the DTI file and the graphics screen if the ENABLE GRAPHICS command has also been given.

--------------------------------------------------------------------------------
Messages:

The following messages are specific to the FILEOUT command:


*** ERROR *** Specifying command FILEOUT
Filename is missing

--------------------------------------------------------------------------------
Examples:


SLOPES> FILEOUT DUA3:[DEMONSTRATION]IDAHO<CR>
SLOPES>

HEIGHT_DIFFERENCE COMMAND

--------------------------------------------------------------------------------
HEIGHT_DIFFERENCE

--------------------------------------------------------------------------------

FORMAT:         HEIGHT_DIFFERENCE

--------------------------------------------------------------------------------
Command parameters:_None

--------------------------------------------------------------------------------
DESCRIPTION:

This command calculates a height difference map indicating the difference in height between each DTM node and its neighbours. If the ENABLE AVERAGE command has been given then the average height difference is output. Otherwise the maximum height difference is calculated.

Output is displayed on the graphics screen if ENABLE GRAPHICS command has been given and/or to a DTI file if the FILEOUT command has been issued.

HEIGHT_DIFFERENCE information is only calculated matrix points that lie within the currently defined WINDOW.

Typing (Pressing the Ctrl and C keys together) aborts the calculation and display of height difference.

--------------------------------------------------------------------------------
Messages:

The following error messages are specific to the HEIGHT_DIFFERENCE command.


*** ERROR *** Specifying command HEIGHT_DIFFERENCE
Output medium not specified
Use ENABLE GRAPHICS or FILEOUT commands

*** ERROR *** Specifying command HEIGHT_DIFFERENCE
No input DTI file had been specified

--------------------------------------------------------------------------------
Examples:

SLOPES>HEIGHT_DIFFERENCE
SLOPES>

HELP

--------------------------------------------------------------------------------
HELP

--------------------------------------------------------------------------------

FORMAT:          HELP [command]

--------------------------------------------------------------------------------
Command parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

A brief description is given of the function and format of the specified command. If no parameter is specified then a complete list of available commands are output.

--------------------------------------------------------------------------------
Messages: _None

--------------------------------------------------------------------------------
Examples:

SLOPES>HELP SLOPE
SLOPES>

LABEL POSITION

--------------------------------------------------------------------------------
LABEL POSITION

--------------------------------------------------------------------------------

FORMAT:         LABEL POSITION screenx screeny

--------------------------------------------------------------------------------
Command parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

The position of the user annotation is defined

The position is specified in screen pixel units, with respect to the SW corner of the screen.

--------------------------------------------------------------------------------
Messages:


The following messages are specific to the LABEL and LABEL POSITION commands.


*** ERROR *** Specifying command LABEL
Command qualifiers are POSITION or SIZE

--------------------------------------------------------------------------------
Examples:

SLOPES>LABEL POSITION 400 200
SLOPES>

LABEL SIZE

--------------------------------------------------------------------------------
LABEL SIZE

--------------------------------------------------------------------------------

FORMAT:         LABEL SIZE font-size

--------------------------------------------------------------------------------
Command parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

The command LABEL SIZE is used to define the size of any text output to a graphics screen using the DRAW LABEL command.

The font_size parameter controls the relative size of the text; size 1 is the smallest, and size 4 is the largest. The actual size of the output text screen will vary with the size of the graphics device screen, though the relative sizes of the text will remain constant.

--------------------------------------------------------------------------------
Messages:


The following messages are specific to the LABEL and LABEL SIZE commands.


*** ERROR *** Specifying command LABEL
Command qualifiers are POSITION, or SIZE


*** ERROR *** Specifying command LABEL SIZE
Command requires an integer in the range 1 to 4

--------------------------------------------------------------------------------
Examples:

SLOPES>LABEL SIZE 3
SLOPES>

LEGEND POSITION

--------------------------------------------------------------------------------
LEGEND POSITION

--------------------------------------------------------------------------------

FORMAT:         LEGEND POSITION screenx screeny

--------------------------------------------------------------------------------
Command parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

The position of the legend is defined

The position is specified in screen pixel units, with respect to the bottom left corner of the screen.

--------------------------------------------------------------------------------
Messages:


The following messages are specific to the LEGEND and LEGEND POSITION commands.


*** ERROR *** Specifying command LEGEND
Command qualifier is POSITION

--------------------------------------------------------------------------------
Examples:

SLOPES>LEGEND POSITION 400 200
SLOPES>

LUT

--------------------------------------------------------------------------------
LUT

--------------------------------------------------------------------------------

FORMAT:         LUT  [keyword] file-spec

--------------------------------------------------------------------------------
Command parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

This command is used to read in a new look up colour table. The colour table is a file containing the RGB definitions for a series of colour values. These values are used when images are displayed on the screen. If the optional keyword argument is omitted, then the specified colour table is read in immediately.

The keyword argument is used to to specify the colour table to be used when subsequent SLOPE, ASPECT, SHADE or HEIGHT_DIFFERENCE maps are generated on the graphics screen.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the LUT command.


*** ERROR *** Specifying command LUT
Filename is missing


*** ERROR *** Specifying command LUT
A graphics device is not selected

--------------------------------------------------------------------------------
Examples:

SLOPES>LUT SHADES YELLOW.DAT
SLOPES>LUT YELLOW

REDUCE

--------------------------------------------------------------------------------
REDUCE

--------------------------------------------------------------------------------

FORMAT:         REDUCE

--------------------------------------------------------------------------------
Command Parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

The screen image is reduced by a factor of 2 using pixel replication. If the command is repeatedly given the display will continue to be enlarged until the maximum magnification (x 16) is reached.

This command has effect only on a graphics device which supports hardware pixel replication.

--------------------------------------------------------------------------------
Messages

Display is at minimum magnification

--------------------------------------------------------------------------------
Examples:

SLOPES>REDUCE
SLOPES>

REFLECTANCE_MAP

--------------------------------------------------------------------------------
REFLECTANCE_MAP

--------------------------------------------------------------------------------

FORMAT:         REFLECTANCE__MAP index

--------------------------------------------------------------------------------
Command Parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

This command is used to specify the reflectance map to be used in the generation of a shaded relief map. The three reflectance maps are as follows:-


                1               = Peucker's piecewise linear approximation 
                                  to a Lambertian surface.
                2 (default)     = Reflectance from a Lambertian surface.
                3               = Wiechel's projected incident angle
                                  algorithm.

Note: Reflectance Map 1 assumes the source of illumination to be in the standard 'hill-shading' position ie. in the North West at 450, and current sun angle and sun position settings are not used by this algorithm.

--------------------------------------------------------------------------------
Messages
The following message is specific to the REFLECTANCE_MAP command.


*** ERROR *** Specifying command REFLECTANCE_MAP
Command requires an integer between 1 and 3

--------------------------------------------------------------------------------
Examples:

SLOPES>REFLECTANCE_MAP 1
SLOPES>

SETUP MAP COMMAND

--------------------------------------------------------------------------------
SETUP MAP

--------------------------------------------------------------------------------

FORMAT:          SETUP MAP

--------------------------------------------------------------------------------
DESCRIPTION:

The SETUP MAP command allows a source document to be registered to the input DTM.

In order to register the map and a DTM, the DTM should have first been specified, and a source document should have been securely attached to the surface of a digitising table.

On giving the command you will be asked to digitise 4 rectangular registration points. The registration points represent 4 points on the map that correspond to the 4 corners of the DTM. The points are digitised in the order top left (NW), bottom left (SW), bottom right (SE) and top right (NE) using any button on the table puck. A point should be digitised in response to a prompt on the terminal.
An error message is generated if any of the angles of the digitised rectangle are less than 88 degrees, or greater than 92 degrees (ie. if the corner points of the rectangle are more than 2 degrees off rectangular). In this case you will be asked to redigitise the 4 registration points.
Setup of the map may be aborted using (pressing the Ctrl and Z keys together).

Following the registration of a map to the DTM, coordinate values required by the WINDOW command, may be input using the table puck.

--------------------------------------------------------------------------------
Messages:

The following error messages are specific to the SETUP and SETUP MAP commands:


*** ERROR *** Specifying command SETUP
Command qualifiers are MAP or MENU

*** ERROR *** Specifying command SETUP MAP
Command is invalid if the table has not been initialised

*** ERROR *** Specifying command SETUP MAP
The input DTM must be specified before SETUP MAP

*** ERROR *** Setting up MAP
Badly digitised corner points; try again

--------------------------------------------------------------------------------
Examples:

SLOPES>SETUP MAP


Digitise map NW corner>

Digitise map SW corner>

Digitise map SE corner>

Digitise map NE corner>


SLOPES>

SETUP MENU COMMAND

--------------------------------------------------------------------------------
SETUP MENU

--------------------------------------------------------------------------------

FORMAT:          SETUP MENU

--------------------------------------------------------------------------------
DESCRIPTION:

The SETUP MENU command allows the SLOPES menu to be positioned on the digitising table.

On giving the command you will be asked to digitise the 4 corners points of the menu. The corners are digitised in the order top left (NW), bottom left (SW), bottom right (SE) and top right (NE) using any button on the table puck. A point should be digitised in response to a prompt on the terminal.
An error message is generated if any of the angles of the digitised rectangle are less than 88 degrees, or greater than 92 degrees (ie. if the corner points of the rectangle are more than 2 degrees off rectangular). In this case you will be asked to redigitise the 4 menu corner points.
Setup of the menu may be aborted using (pressing the Ctrl and Z keys together).

Once a menu has been positioned on the table, it is possible to enter many of the SLOPES commands by digitising a point in the appropriate menu box. If a command requires a parameter argument, you should enter the parameter in response to the prompt on the terminal, using the keyboard.

--------------------------------------------------------------------------------
Messages:

The following error messages are specific to the SETUP and SETUP MENU commands:


*** ERROR *** Specifying command SETUP
Command qualifiers are MAP or MENU

*** ERROR *** Specifying command SETUP MENU
Command is invalid if the table has not been initialised

*** ERROR *** Setting up MENU
Badly digitised corner points; try again

--------------------------------------------------------------------------------
Examples:

SLOPES>SETUP MENU


Digitise menu NW corner>

Digitise menu SW corner>

Digitise menu SE corner>

Digitise menu NE corner>


SLOPES>

SHADE COMMAND

--------------------------------------------------------------------------------
SHADE

--------------------------------------------------------------------------------

FORMAT:         SHADE

--------------------------------------------------------------------------------
Command parameters:_None

--------------------------------------------------------------------------------
DESCRIPTION:

This command calculates a shaded relief map.

Output is displayed on the graphics screen if ENABLE GRAPHICS command has been given and/or to a DTI file if the FILEOUT command has been issued.

The description section contains more information on the algorithms used in the generation of a shaded relief map.

SHADE information is only calculated for matrix points that lie within the currently defined WINDOW.

Typing (Pressing the Ctrl and C keys together) aborts the calculation and display of a shaded relief map.

--------------------------------------------------------------------------------
Messages:

The following error messages are specific to the SHADE command.

*** ERROR *** Specifying command SHADE 
Output medium not specified
Use ENABLE GRAPHICS or FILEOUT commands

*** ERROR *** Specifying command SHADE
No input DTI file had been specified

--------------------------------------------------------------------------------
Examples:

SLOPES>SHADE
SLOPES>

SHOW ANNOTATION

--------------------------------------------------------------------------------
SHOW ANNOTATION

--------------------------------------------------------------------------------

FORMAT:          SHOW ANNOTATION

--------------------------------------------------------------------------------
Command parameters: _None

--------------------------------------------------------------------------------
DESCRIPTION:

Outputs details of the label and legend positions, and label size to the terminal.

--------------------------------------------------------------------------------
Messages:

The following error messages are specific to the SHOW command.


*** ERROR *** specifying command SHOW
SHOW qualifiers are ANNOTATION, ASPECT, ENABLE, FILES, 
HEIGHT_DIFFERENCE, SHADE or SLOPE

--------------------------------------------------------------------------------
Examples:

SLOPES>SHOW ANNOTATION


Current label  setting:
Position: X 150 Y 75  Size 2
Current legend setting:
Position: X 50 Y 150  
 

SLOPES>

SHOW ASPECT COMMAND

--------------------------------------------------------------------------------
SHOW ASPECT

--------------------------------------------------------------------------------

FORMAT:         SHOW ASPECT

--------------------------------------------------------------------------------
Command parameters:_None

--------------------------------------------------------------------------------
DESCRIPTION:

Information about the current aspect parameter settings is displayed on the terminal.

--------------------------------------------------------------------------------
Messages:

The following error messages are specific to the SHOW command.


*** ERROR *** specifying command SHOW
SHOW qualifiers are ANNOTATION, ASPECT, ENABLE, FILES, 
HEIGHT_DIFFERENCE, SHADE or SLOPE

--------------------------------------------------------------------------------
Examples:

SLOPES>SHOW ASPECT

 
Z limits          : -32766 to 32767
Angular step      : 30
Look up table     : LSL$LOOKUP:SLOPES.DAT
Aspect colour image selected
 

SLOPES>

SHOW ENABLE COMMAND

--------------------------------------------------------------------------------
SHOW ENABLE

--------------------------------------------------------------------------------

FORMAT:         SHOW ENABLE

--------------------------------------------------------------------------------
Command parameters:_None

--------------------------------------------------------------------------------
DESCRIPTION:

Displays the current status of all the SLOPES options that may be enabled or disabled using the ENABLE and DISABLE commands.

The name of the option is shown, followed by either the word ON or OFF to indicate its current status.

If the command SHOW ENABLE is used before any ENABLE or DISABLE commands have been given, the default status of the options is displayed.

--------------------------------------------------------------------------------
Messages:

The following error messages are specific to the SHOW command.

SHOW qualifiers are ANNOTATION, ASPECT, ENABLE, FILES, 
HEIGHT_DIFFERENCE, SHADE or SLOPE

--------------------------------------------------------------------------------
Examples:

SLOPES>SHOW ENABLE

 
Current status:
 
ABSOLUTE          On       AVERAGE           On       CLASSIFY         Off     
 
CLEAR             On       GRAPHICS         Off       GREYSCALE        Off      

LEGEND            On       NULL_BORDER      Off       PERCENT          Off     

RECENTRE          On       TABLE            Off       TEXT              On     
  

SLOPES>

SHOW FILES COMMAND

--------------------------------------------------------------------------------
SHOW FILES

--------------------------------------------------------------------------------

FORMAT:         SHOW FILES

--------------------------------------------------------------------------------
Command parameters:_None

--------------------------------------------------------------------------------
DESCRIPTION:

This command displays information about the currently selected input and output DTI files.

Details extracted from the header of the input DTM are displayed on the terminal, along with details of the current window or area of interest.

The header values are shown in the current units of measurement. This is dependent on the header type of the input file, or may be set explicitly using the UNITS command. By default or if the ENABLE ABSOLUTE command has been given then metre or projection values are expressed in absolute values.

--------------------------------------------------------------------------------
Messages:

The following error messages are specific to the SHOW command.


*** ERROR *** specifying command SHOW
SHOW qualifiers are ANNOTATION, ASPECT, ENABLE, FILES, 
HEIGHT_DIFFERENCE, SHADE or SLOPE

--------------------------------------------------------------------------------
Examples:

SLOPES>SHOW FILES


File    :  LSL$DTI:matrix_test.DTI
Header  :  LSLA  Data:  WORD

Units are metres

Matrix Coverage   SW:  450000.00   80000.00    NE:  460000.00   90000.00
Matrix Window     SW:  450000.00   80000.00    NE:  460000.00   90000.00
Matrix Interval    E:      50.00                N:     100.00
Value Range         :-32766   to  32767

File LSL$DTI:MATRIX_TEST.SLP selected for output

SLOPES>

SHOW HEIGHT_DIFFERENCE COMMAND

--------------------------------------------------------------------------------
SHOW HEIGHT_DIFFERENCE

--------------------------------------------------------------------------------

FORMAT:         SHOW HEIGHT_DIFFERENCE

--------------------------------------------------------------------------------
Command parameters:_None

--------------------------------------------------------------------------------
DESCRIPTION:

Information about the current height difference parameter settings is displayed on the terminal.

--------------------------------------------------------------------------------
Messages:

The following error messages are specific to the SHOW command.


*** ERROR *** specifying command SHOW
SHOW qualifiers are ANNOTATION, ASPECT, ENABLE, FILES, 
HEIGHT_DIFFERENCE, SHADE or SLOPE

--------------------------------------------------------------------------------
Examples:

SLOPES>SHOW HEIGHT_DIFFERENCE

 
Calculation of average height difference selected
Z limits          : -32766 to 32767
Value range       : 0 to 60
Z Scale           : 1
Number of steps   : 12
Look up table     : LSL$LOOKUP:SLOPES.DAT
Step upper limits :  5 10 15 20 25 30 35 40 45 50 
                  : 55 60 
Colour indices    :  2  3  4  5  6  7  8  9 10 11 
                  : 12 13 
 

SLOPES>

SHOW SHADE COMMAND

--------------------------------------------------------------------------------
SHOW SHADE

--------------------------------------------------------------------------------

FORMAT:         SHOW SHADE

--------------------------------------------------------------------------------
Command parameters:_None

--------------------------------------------------------------------------------
DESCRIPTION:

Information about the current shade parameter settings is displayed on the terminal.

--------------------------------------------------------------------------------
Messages:

The following error messages are specific to the SHOW command.


*** ERROR *** specifying command SHOW
SHOW qualifiers are ANNOTATION, ASPECT, ENABLE, FILES, 
HEIGHT_DIFFERENCE, SHADE or SLOPE

--------------------------------------------------------------------------------
Examples:

SLOPES>SHOW SHADE

 
Sun position   : 315.0
Sun angle      : 45.0
Reflectance map: 2
Z Scale        : 1
Look up table  : LSL$LOOKUP:GREY.DAT
 

SLOPES>

SHOW SLOPE COMMAND

--------------------------------------------------------------------------------
SHOW SLOPE

--------------------------------------------------------------------------------

FORMAT:         SHOW SLOPE

--------------------------------------------------------------------------------
Command parameters:_None

--------------------------------------------------------------------------------
DESCRIPTION:

Information about the current slope parameter settings is displayed on the terminal.

--------------------------------------------------------------------------------
Messages:

The following error message is specific to the SHOW command.


*** ERROR *** specifying command SHOW
SHOW qualifiers are ANNOTATION, ASPECT, ENABLE, FILES, 
HEIGHT_DIFFERENCE, SHADE or SLOPE

--------------------------------------------------------------------------------
Examples:

SLOPES>SHOW SLOPE

 
 
Gradient algorithm: 1
Z limits          : -32766 to 32767
Z Scale           : 1
Gradient range    : 0 to 60
Gradient units    : Degrees of Slope
Number of steps   : 12
Look up table     : LSL$LOOKUP:SLOPES.DAT
Step upper limits :  5 10 15 20 25 30 35 40 45 50 
                  : 55 60 
Colour indices    :  2  3  4  5  6  7  8  9 10 11 
                  : 12 13 
 

SLOPES>

SLOPE COMMAND

--------------------------------------------------------------------------------
SLOPE

--------------------------------------------------------------------------------

FORMAT:         SLOPE [algorithm]

--------------------------------------------------------------------------------
Command parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

This command calculates a slope map indicating the gradient at each DTM node and using the specified algorithm. Further details of the SLOPE algorithms is contained in the description section.

Output is displayed on the graphics screen if ENABLE GRAPHICS command has been given and/or to a DTI file if the FILEOUT command has been issued.

If output is to a DTI file then if the ENABLE CLASSIFY has been given each classified index, as defined by the STEP and COLOUR commands are output to the DTI file. Otherwise the actual calculated slope values are output. On completion of SLOPE calculation, details of the DTI file produced are output to the terminal.

Values are calculated in degrees unless the ENABLE PERCENT command has been given, in which case values are output as percentage slope. The ZSCALE command may be used to increase the slope values by the specified factor.

SLOPE information is only calculated for the currently defined WINDOW.

Typing (Pressing the Ctrl and C keys together) aborts the display of and calculation of slope.

--------------------------------------------------------------------------------
Messages:

The following error messages are specific to the SLOPE command.


*** ERROR *** Specifying command SLOPE
Output medium not specified
Use ENABLE GRAPHICS or FILEOUT commands

*** ERROR *** Specifying command SLOPE
No input DTI file had been specified

*** WARNING *** Specifying command SLOPE
Gradient algorithm should be in the range 1 to 5
Current gradient algorithm will be used

--------------------------------------------------------------------------------
Examples:

SLOPES>SLOPE 1
SLOPES>

SPAWN

--------------------------------------------------------------------------------
SPAWN

--------------------------------------------------------------------------------

FORMAT:          SPAWN command

--------------------------------------------------------------------------------
Command parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

SPAWN allows a DCL command to be obeyed from within the SLOPES program. This is to allow file management operations such as DIRECTORY, DELETE and RENAME to be carried out during program execution.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the SPAWN command.


*** ERROR *** Specifying command SPAWN
SPAWN requires a valid DCL command

--------------------------------------------------------------------------------
Examples:

SLOPES>SPAWN DIRECTORY LSL$DTI

Directory DUA0:[DTI]

AFRICA.DTI;2      LS41.DTI;1       WALES.DTI;3         TEST.DTI;13

Total of 3 files

SLOPES>SPAWN RENAME AFRICA.DTI SOUTHAMERICA.DTI
SLOPES>

STEP

--------------------------------------------------------------------------------
STEP

--------------------------------------------------------------------------------

FORMAT:          STEP values[...]

--------------------------------------------------------------------------------
Command parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

This command divides the calculated values for the SLOPE and HEIGHT_DIFFERENCE commands, into a series of steps which are displayed in different colours. A single value denotes a constant step interval, while a variable step interval may be defined by entering up to 7 values. A particular colour index may be associated with each step by means of the COLOUR command.

The default value is a step of 5.

The colour index that will be associated with each step may by examined by means of the command SHOW SLOPE or SHOW HEIGHT_DIFFERENCE.

--------------------------------------------------------------------------------
Messages:


The following messages are specific to the STEP command.


*** ERROR *** Specifying command STEP
Command requires between 1 and 7 integer values


*** ERROR *** Specifying command STEP
Command requires integer values in the range 1 to "upper-value"


*** WARNING *** Value range exceeded
step "step_number" is truncated to "DTI-value"

--------------------------------------------------------------------------------
Examples:

SLOPES>STEP 10
SLOPES>STEP 1 2 3 5 10 10 10
SLOPES>

SUN_ANGLE

--------------------------------------------------------------------------------
SUN_ANGLE

--------------------------------------------------------------------------------

FORMAT:          SUN_ANGLE angle

--------------------------------------------------------------------------------
Command parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

This command is used to set the angle of elevation of the light source for SHADE calculations.

Reducing the sun angle tends to increase the slope component, and is therefore useful for emphasising slope in less mountainous areas.

The current value of the SUN_ANGLE may be shown by using the SHOW SHADE command.

--------------------------------------------------------------------------------
Messages:


The following messages are specific to the SUN_ANGLE command.


*** ERROR *** Specifying command SUN_ANGLE
Command requires a real value between 0 and 90

--------------------------------------------------------------------------------
Examples:

SLOPES>SUN_ANGLE 30
SLOPES>

SUN_POSITION

--------------------------------------------------------------------------------
SUN_POSITION

--------------------------------------------------------------------------------

FORMAT:          SUN_POSITION angle

--------------------------------------------------------------------------------
Command parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

This command is used to set the position of the light source for SHADE calculations. The default value of 315 degrees is chosen because it represents normal visual perception of the terrain.

It may be useful to change the sun position to show more clearly terrain features lying in particular direction.

The current value of the SUN_POSITION may be shown by using the SHOW SHADE command.

--------------------------------------------------------------------------------
Messages:


The following messages are specific to the SUN_POSITION command.


*** ERROR *** Specifying command SUN_POSITION
Command requires a real value between 0 and 360

--------------------------------------------------------------------------------
Examples:

SLOPES>SUN_POSITION 45
SLOPES>

UNITS COMMAND

--------------------------------------------------------------------------------
UNITS

--------------------------------------------------------------------------------
FORMAT: UNITS units

--------------------------------------------------------------------------------
Command parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

The UNITS command defines the units of measurement that will be used when defining an area of interest in the currently selected DTI file by means of the WINDOW command.
The command also controls in what format details from the header of the DTI file are displayed, when the SHOW FILES command is given.

The command should be given after defining the an DTI file since an appropriate default units of measurement is set up when the file is opened.

--------------------------------------------------------------------------------
Messages:


The following messages are specific to the UNITS command.


*** ERROR *** Specifying command UNITS
Command should be followed by MATRIX, METRES, LATLONG, SECONDS or PROJECTION
Current setting is "units"


*** ERROR *** Specifying command UNITS
Command qualifier is invalid for the input file

--------------------------------------------------------------------------------
Examples:


SLOPES> UNITS MATRIX<CR>
SLOPES>

VALUE_RANGE COMMAND

--------------------------------------------------------------------------------
VALUE_RANGE

--------------------------------------------------------------------------------


FORMAT: VALUE_RANGE lower_value upper_value

--------------------------------------------------------------------------------
Command parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

The VALUE_RANGE command is used to define the range of values output when the SLOPES or HEIGHT_DIFFERENCE commands are given.

Cells with values outside the range appear in black on the displayed image. They are output as null values in the output DTI file.

--------------------------------------------------------------------------------
Messages:


The following message is specific to the VALUE_RANGE command.


*** ERROR *** Specifying command VALUE_RANGE Lower value exceeds upper value

--------------------------------------------------------------------------------
Examples:


SLOPES> VALUE_RANGE 5 15<CR>
SLOPES>

WAIT

--------------------------------------------------------------------------------
WAIT

--------------------------------------------------------------------------------

FORMAT:          WAIT interval

--------------------------------------------------------------------------------
Command parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

This command suspends program execution for the specified time interval. It is useful for demonstration purposes if SLOPES is being run from a command file.

--------------------------------------------------------------------------------
Messages:


The following messages are specific to the WAIT command.


*** ERROR *** Specifying command WAIT
Command requires a real in the range 1 to 1000

--------------------------------------------------------------------------------
Examples:

SLOPES>WAIT 5.0
SLOPES>

WINDOW COMMAND

--------------------------------------------------------------------------------
WINDOW

--------------------------------------------------------------------------------

FORMAT:         WINDOW xmin ymin xmax ymax

--------------------------------------------------------------------------------
Command parameters:

--------------------------------------------------------------------------------
DESCRIPTION:

The WINDOW command is used to limit display to a particular rectangular geographical area. Only nodes in the DTI file that lie within this area are drawn when the DISPLAY command is given.
The area of interest should lie within the geographical bounds of the DTI file.

If the logical name LSL$MATRIX_DEFAULT_WINDOW is defined with a value of "1", then a default area of interest defined in matrix units of bottom left hand corner 1,1 and top right hand corner 200,200 is set when the file is opened. If the logical name is absent or has any other value, or if the input DTI file has fewer than 200 columns or 200 rows, then a default window equivalent to the total matrix is set.

If a digitising table is available, and a map has been registered to the DTI file, the coordinates of the window may be defined using any button on the table puck.

--------------------------------------------------------------------------------
Messages:

The following messages are specific to the WINDOW command:


*** ERROR *** Specifying command WINDOW
Command not available during editing operation


*** ERROR *** Specifying command WINDOW
Command requires 4 coordinate values


*** ERROR *** Specifying command WINDOW
DTI file has not yet been opened


*** ERROR *** Specifying command WINDOW
NE coordinates should exceed SW coordinates


*** ERROR *** Specifying command WINDOW
Unable to use supplied LAT LONG values


*** WARNING *** Specified window exceeds matrix limits
Window will be truncated to fit

--------------------------------------------------------------------------------
Examples:

SLOPES>WINDOW 1 1 200 200
SLOPES>UNITS LATLONG
SLOPES>WINDOW 42 00 00N 3 00 00E 42 30 00N 2 58 40E
SLOPES>

ZLIMITS COMMAND

--------------------------------------------------------------------------------
ZLIMITS

--------------------------------------------------------------------------------

FORMAT:          ZLIMITS lower_height upper_height

----------------------------------------------