User's Guide

NOMFIL

Perform stepwise nominal filtering using REGLABEL, FLAG, SMOOTH, and ABS.

Function:

Stepwise nominal filtering. Calls REGLABEL, FLAG, SMOOTH, ABS in sequence up to five times. Each time it can have different values for the parameters.

Parameters:

IN

Input image. Single band image containing BYTE, INTEGER*2, or INTEGER*4 pixel data. Window options may be specified. The input image is usually a classified image.

OUT

Output image. The name of the output image after the sequence of REGLABEL, FLAG, SMOOTH, and ABS has been run. The output image will be a single-band image which is the same size as the input image. The series of functions will run as many times as the number of OUT names.

DFLTHRSH

Default area threshold. Flags regions whose class values are not found in THRSHOLD. DFLTHRSH is used by FLAG.

DFLTWGHT

Default weight value. Used when the combination of flagged and replacement classes is not found in WEIGHTLT. DFLTWGHT is used in SMOOTH.

REGLCNCT(FOUR,FOUR,FOUR,FOUR,FOUR)

Contiguity checking criteria. Used by REFLABEL as the value for CONNECT.

  = FOUR:   Four-way checking.  Checks only horizontally
	    and vertically adjacent pixels for contiguity.
  = EIGHT:  Eight-way checking.  Checks horizontally, 
	    vertically, and diagonally adjacent pixels
	    for contiguity.

THRSHOLD(NONE,NONE,NONE,NONE,NONE)

Threshold labeled table. Contains class values and corresponding thresholds to be used in determination of whether to flag regions. THRSHOLD is used by FLAG as the value for INLT.

MASKCLSS(0,0,0,0,0)

Class value of mask regions. All regions that have a class value that matches this mask class will be changed to 0 (background). MASKCLSS is used by FLAG.

WEIGHTLT(NONE,NONE,NONE,NONE,NONE)

Weight labeled table. Contains class pairs and corresponding weight values to be used in determining which class values should replace the flagged pixels' class values. WEIGHTLT is INLT for SMOOTH.

SMTHCNCT(EIGHT,EIGHT,EIGHT,EIGHT,EIGHT)

Candidate connectedness criteria. Used by SMOOTH as the value for CONNECT.

  = FOUR:   Four-way connected.  Candidate classes must
	    be either vertically or horizontally 
	    adjacent to the flagged pixel.
  = EIGHT:  Eight-way connected.  Candidate classes may
	    be vertically, horizontally, or diagonally
	    adjacent to the flagged class.

HISTFLG(NO)

Histogram flag. After SMOOTH is completed, a histogram may be generated by PIXCOUNT. The histogram is written to a temporary file.

  = YES:  Generate histogram.  
  = NO:   No histogram.

DELFLG(NO)

Delete flag. Delete the temporary and intermediate output images created at the end of each sequence of REGLABEL, FLAG, SMOOTH, and ABS except for the last one.

  = YES:  Delete intermediate images.
  = NO:   Do not delete intermediate images.  

Example:

1. LAS> nomfil in=classified out=(nomfil1, nomfil2) dfltthrsh=(10,25) dfltwght=(10,10) thrshold=(threshlt.1, threshlt.2) weightlt=(pairlt.1, pairlt.2) histflg=yes delflg=yes

   The sequence of REGLABEL, FLAG, SMOOTH, ABS is run twice with NOMFIL2 as the final output image. A histogram is generated after each run of SMOOTH.

Description/Algorithm:

NOMFIL initiates up to five sequential executions of REGLABEL, FLAG, SMOOTH, ABS. The sequence is started by running REGLABEL on the value specified in IN. FLAG is performed on the result of REGLABEL. The result is sent to SMOOTH. If a histogram is requested in HISTFLG, PIXCOUNT is run on the result of SMOOTH. The histogram is written to a file called "SMOOTH.HIST#", where # is based on the number of the iteration of the processing sequence. And finally, ABS is executed. If OUT(<n+1>) is not specified, NOMFIL stops and OUT(<n>) is the final output image. If OUT(<n+1>) is specified, the sequence is started again with OUT(<n>) as the input image to REGLABEL. If DELFLG=YES, all temporary and intermediate OUT(<n>) images are deleted.

Nonfatal Error Messages:

None.

Fatal Error Message:

1. [nomfil-count] Parameter count not consistent

   The number of values in DFLTHRSH and DFLTWGHT cannot be less than the number of values entered in OUT.

User Notes:

1. The following diagram illustrates the processing flow for area filtering:

   
            [ Classified Image ]
                      |
                      |
            [     REGLABEL     ]          
                      |
                      |
            [       FLAG       ]          
                      |
                      |
            [      SMOOTH      ]
                      |
                      |
            [  smoothed image  ]
                      |
                      |
            [        ABS       ]
   
   

2. For more specific help on the parameters for NOMFIL, the user should reference the corresponding parameters in the individual user guides for REGLABEL, FLAG, SMOOTH, and ABS.