User's Guide

CORRVIEW

Creates an image of tie point pairs with tie points marked as a box

Function:

Creates an image of tie point pairs with tie points marked as a box. CORRVIEW reads a Tie Point Location (TPL) file, extracts control point neighborhoods for tie points from both the search and reference images and creates an image of these control point neighborhoods. The output image will contain the search control point neighborhood on the left and the reference control point neighborhood on the right. This is useful for verifying an automatic correlation selection process. The output image can be viewed to verify the correct location of tie points.

Parameters:

IN

Input images. The first image is the reference image and the second is the search image. These are the images from which the tie points have been selected. Only one band may be specified form each image. Windowing is not permitted.

INTL

Input tie point location file. The tie point location file containing the tie point coordinate pairs which are used to identify the control point neighborhoods.

OUT

Output image. The output image containing the expanded control point neighborhoods with the tie points pairs marked with a box and annotated with the tie point name. The box is a 15 x 15 pixel box centered on the tie point. The text is the name of the tie point as given in the TPL file. Each pair of expanded reference and search control point neighborhoods will be separated by pixels of BACKGRND intensity. OUT will be a single band image.

CHARGREY(255)

Character grey value. The grey value that the annotation text and the box which marks the tie point will be.

BACKGRND(0)

Background value. The pixel value used in the background of the output image.

OUTNS(1791 )

Output number of samples. The number of samples that will be in OUT. The number of lines will depend on the number of valid tie points specified and OUTNS. If OUTNS is less than the minimum size of the expanded control point neighborhoods, OUTNS is reset to this minimum size.

Examples:

1. LAS> corrview in=(ref,srch) out=temp intl=matchpts outns=1024

   The tie point location file MATCHPTS is read. Small windows which surround the tie points are extracted from both the REF and SRCH images. These windows are then enlarged by a factor of 4. Annotation text is added to identify each point, and the enlarged windows are combined in TEMP, REF on the right and SRCH on the left. TEMP will have 1024 samples. The number of lines will depend on the number of valid tie points.

Description/Algorithm:

Creates an image of tie point pairs with tie points annotated. A Tie Point Location File (TPL) is read. Control point neighborhoods which surround each tie point are extracted from the reference and search images. These neighborhoods are expanded by a factor of four using bilinear interpolation. Annotation text is added to identify each point. The intensity value of the text is specified by CHARGREY. This text consists of the tie point name which is in the TPL file, and of a box which surrounds the actual point on the image. The enlarged reference and search control point neighborhoods will be combined and written to OUT. The next pair of enlarged control point neighborhoods will be separated from the previous pair so that the pairing is obvious when viewed. Pixels which are neither image data nor annotation text will have an intensity of BACKGRND.

Nonfatal Error Messages:

1. [corrview-box] Error writing tiepoint box

   Part or all of the enlarged tiepoint box is too close to the edge of the image. The part that will still be visible is written.

Fatal Error Messages:

1. [corrview-alloc] Error allocating dynamic memory

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

2. [corrview-band] More than one band specified

   More than one band was specified for an input image. Rerun with only one band specified for each input image.

3. [corrview-fatal] Fatal error encountered

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

4. [corrview-open] Error opening TPL file

   An error occurred while opening the tie point location file. Check to see that the protections are set for the file.

5. [corrview-valid] No tie points are valid

   None of the tie points in the tie point location file are valid. Rerun with valid tie points.

6. [corrview-window] Windowing not allowed

   A window was specified with one of the input images. Rerun without windowing options specified.

User Notes:

1. A related program is TIEPTS.

2. CORRVIEW is generally run after an automatic tie point correlation process to verify (by viewing OUT) the tie points that were correlated.