User's Guide

TIEMERGE

Merges two tie point selection files

Function:

Merges entries from two tie point selection files to form either a merged tie point file for use in image correlation or a tie point location file for use in the tie point fitting process. In normal usage, one of the two input files contains coordinates corresponding to a reference coordinate system, the other corresponding to the search coordinate system. Examples of this are image-to-image registration and image-to-map (geographic) registration.

Parameters:

Subcommand -NOCORR:
Writes a tie point location file for the tie point fitting process. This option is used whenever automatic correlation is not desired or is not possible. The resulting file may be read directly by POLYFIT.

INTS
Input tie point selection files. The first filename is treated as the reference set of points and the second is treated as the search set of points.

OUTTL
Output tie point location file. This file contains a record for each tie point selected from INTS(1) with a corresponding record in INTS(2).

CONFLG(NO)
Confirmation flag. Specifies whether or not the user will be prompted to verify the merging of each reference tie point with a corresponding search tie point into the output file. 


  = YES:  Confirm merge
  = NO:   Do not confirm merge
Subcommand -PRECORR:
Writes a merged tie point file for the correlation process. This option is used when automatic correlation is desired to refine tie point locations. The resulting file is readable by CORRELATE.

INTS
Input tie point selection files. The first filename is treated as the reference set of points and the second is treated as the search set of points.

OUTMT
Output merged tie point file. This file contains a record for each tie point selected from INTS(1) with a corresponding record in INTS(2).

CONFLG(NO)
Confirmation flag. Specifies whether or not the user will be prompted to verify the merging of each reference tie point with a corresponding search tie point into the output file. 


  = YES:  Confirm merge
  = NO:   Do not confirm merge

Examples:

  1. LAS> tiemerge-nocorr ints=(tie.ref,tie.sea) outtl=merged conflg=no

    Reference tie points in the TIE.REF file are merged with search tie points in the TIE.SEA file. Successful merges are written to the tie point location file MERGED. The user is not prompted to verify each merge.

  2. LAS> tiemerge-precorr ints=(tie.ref,tie.sea) outmt=merged conflg=yes

    As each search tie point selection record is read, the user is prompted to confirm the merging of that point. If the user responds with "Y," the reference file is scanned for the corresponding tie point. If the tie point is contained in the reference file, the tie points are merged and written to the output merged tie point file MERGED.

Description/Algorithm:

TIEMERGE reads the headers of the two tie point selection files and obtains the file type (reference or search). Next, TIEMERGE begins reading records from the search file. (A common processing scenario would be to have a large number of reference points for a given area, with a smaller number of search points representing the "best" control over the area). For each record, the tie point name is obtained, and if CONFLG=YES, the user is asked if the named tie point should be merged. If the tie point is to be merged, TIEMERGE locates the corresponding record from the reference file and merges the records to form an output tie point record of the chosen output file type.

Nonfatal Error Messages:

    None.

Fatal Error Messages:

  1. [tiemerge-fatal] Fatal error encountered

    The error message that is displayed immediately preceding this message is the specific error that was encountered. Processing is terminated.

  2. [tiemerge-alloc] Error allocating memory

    An error occurred allocating memory. Rerun the function, and if the error reoccurs, contact the system manager.

User Notes:

  1. The reference coordinates are those used by POLYFIT as the X (independent) variables in calculating the least squares polynomials from the coordinate pairs in the tiepoint location file. Likewise, the search coordinates are the Y (dependent) variables in the least squares fitting. Two examples using this information follow. 

        a.  In registering one image to another, the image that is 
        being registered to is the reference and the image being 
        fitted to the other is the search.

    b.  In developing a transformation to create a raster image 
        registered to a given map projection, the user would use 
        digitized control point coordinates from a map as the 
        reference and the corresponding control points (image 
        coordinates) from the input image as the search.
  2. The height and width of the reference subimage are not transferred if the user specifies two tie point selection files whose modes indicate they are both search images.

  3. The search area in the search image is not transferred if the user specifies two tie point selection files whose modes indicate they are both reference images.