User's Guide

RTABLE

Generates a resampling weight table file

Function:

Generates resampling weight table files for use in the rectification process. The SINC subcommand allows the user to create a sin(x)/x resampling kernel with or without a Hanning window applied. The FILE subcommand allows the user to create various resampling weight tables from an input file(s) containing the inverse point spread function of the resampling technique desired. The FILE subcommand may be used for creating resampling weight table files for the restoration processes.

Parameters:

Subcommand -SINC:

Generates a sin(x)/x resampling weight table file. Application of a Hanning window is optional.

OUTRWT
Output resampling weight table file. This file contains one, two, or three resampling tables, depending on the values entered in KERNDIM. The resampling weight table file is used by resampling functions when RESAMP=TABLE.

WINDFLG(YES)
Window flag. As an option, a Hanning window can be applied to the sinc function.
  = YES:  Apply window.
  = NO:   Do not apply window.
KERNDIM
Kernel dimensions. Dimensions of the kernel. The maximum kernel size is 16. One kernel dimension should be given for each table. See the User Notes section for an example of usage.

Subcommand -FILE:

Generates a resampling weight table file given an inverse point spread function for the desired resampler.

INFILE
Input file(s). An ASCII file containing the inverse point spread function. One file is given for each dimension (KERNDIM). Refer to the User Notes section for a description of the file format.

OUTRWT
Output resampling weight table file. This file contains one, two, or three resampling tables, depending on the values entered in KERNDIM. The resampling weight table file is used by resampling functions when RESAMP=TABLE.

KERNDIM
Kernel dimensions. Dimensions of the kernel. The maximum kernel size is 16. One kernel dimension should be given for each table. See the User Notes section for an example of usage.

Examples:

LAS> rtable-sinc outrwt=table kerndim=(16,16,0) windflg=yes
A 16 x 16 sin(x)/x resampling weight table file is generated for use with RESAMPLE when RESAMP=TABLE. A Hanning window has been applied to limit the continuous effects of the sinc function to 16 points.
LAS> rtable-file infile=(ipsf.hoz,ipsf.vert) outrwt=table kerndim=(16,16,0)
A 16 x 16 resampling weight table file is generated for use with RESAMPLE when RESAMP=TABLE. The tables are generated from two files containing inverse point spread functions; the first for the horizontal direction, the second for the vertical direction. This method may be used to create resampling weight tables for the restoration process.

Description/Algorithm:

The user entered parameters are obtained from TAE. If the SINC subcommand is chosen, the sin(x)/x (actually x = PI * x) inverse point spread function is calculated. The user is given the option to limit the otherwise continuous sin(x)/x function with a Hanning window. If the FILE subcommand is chosen, the inverse point spread functions are read from disk. RTABLE then generates a resampling weight table file from the inverse point spread functions, regardless of the subcommand chosen. Refer to the Geometric Manipulation Package Overview Document (GEOMPOD) for more information on this process and resampling in general.

Nonfatal Error Messages:

None.

Fatal Error Messages:

[rtable-fatal] Fatal error encountered
The error message that is displayed immediately preceding this message is the specific error that was encountered. Processing is terminated.
[rtable-open] Error opening inverse point spread function file
An error occurred when attempting to open the file containing the inverse point spread function. Check the validity of the file name.
[rtable-read] Error reading inverse point spread function file
An error occurred when attempting to read the file containing the inverse point spread function. Check the file for validity.

User Notes:

A kernel dimension is given for each table created. If KERNDIM=(16,0,0), one table dimensioned to 16 points is created. This is the normal mode when preparing a resampling kernel for CORRECT or XCORRECT. The table is written to the resampling weight table file.
If KERNDIM=(16,16,0), two tables dimensioned to 16 are created. This kernel is used by RESAMPLE. The first table contains the horizontal resampling kernel, the second contains the vertical resampling kernel. The tables are written to the resampling weight table file.
If KERNDIM=(16,16,16), three tables dimensioned to 16 are created. This kernel is used by GEOM when WARPMETH=THREE. The first table contains the horizontal resampling kernel, the second contains the vertical resampling table, and the third contains the "adjusting" horizontal pass kernel. The tables are written to the resampling weight table file.
NOTE: THE GENERATION OF THREE TABLES HAS BEEN RENDERED OBSOLETE BY THE REPLACEMENT OF GEOM WITH RESAMPLE.
INFILE names are entered so they correspond with the kernel dimensions. Refer to User Note 1.
The output resampling weight table file may be displayed or printed with DSPRWT.

INFILE is an ASCII file which contains an inverse point spread function of the desired resampling method. The file may be generated with a text editor or another program. This is the manner in which resampling weight tables for the restoration process are entered into LAS. (Other resampling methods may be entered in this manner as well...) In the file, the inverse point spread function (IPSF) is oriented such that increasing records correspond to increasing samples. Each IPSF increment is assumed to correspond to 1/32 of the input pixel size. The format is as follows:

     REC#, IPSF_VAL (integer, double)  Index of value, space,
                                       Inverse Point Spread 
                                       function value.  This 
                                       record is repeated for 
                                       each IPSF value (usually 
                                       there are 1024 records).


    An example:

              1  0.000000000E+00
              2 -6.183769437E-05
              3 -1.233220682E-04
              4 -1.838580356E-04
              5 -2.428581938E-04
              6 -2.997475676E-04
              7 -3.539694007E-04
              8 -4.049883573E-04
                       :
                       :
                       :
           1022 -1.838580356E-04
           1023 -1.233220682E-04
           1024 -6.183769437E-05