ANSI-C program: gcp_2ras.c
This program is located in the DISP package.
NAME
gcp_2ras - Select corresponding points from two SUN raster or BMP
format images
SYNOPSIS
gcp_2ras <ras-1> <ras-2> <GCP> [mag]
[win_sz]
| ras-1 | SUN raster *.ras or BMP *.bmp format image (left window) |
| ras-2 | SUN raster *.ras or BMP *.bmp format image (right window) |
| GCP | GCP data file (text format) contains the coordinate information from the two images |
| mag | zoom window magnification factor (default=3) ) |
| win_sz | zoom window size before magnification (default=96) |
EXAMPLE
gcp_2ras 05263.mli 24936.mli 05263_24936.gcp
DESCRIPTION
gcp_2ras reads and displays an 2 images in SUN raster or
BMP format. The user can then select corresponding points in the
two images and save the coordinates in a text format file. The
date entered using gcp_2ras are stored in a text format
file that can be edited using a text editor if necessary. The
file format consists of columns of numbers containing the GCP
number, x cross-track pixel coordinate (column), and y
along-track line number of image 1 and the x and y coordinates of
the corresponding point in image-2. Each GCP has a single line
entry in the file.
Using the program is simple. Different mouse buttons perform different functions. Pressing the left button of the mouse moves the center of zoom window to the selected location. GCP points are selected by pressing the right mouse button. A red cross appears at the selected point in the selected image. Next select the corresponding point in the second image. It is possible to change the location of either point in the pair by right clicking at a new position. The coordinates of the points are written to a file by clicking the write GCP button under the zoom windows. If you have been working on a GCP list you can append additional GCP points by simply rerunning the application and entering the name of the previous GCP file on the command line. The previously entered points will be drawn on the image
It is recommended to select at least 10-20 control points over the entire image when selecting points as input to offset_list_fitm.c This will lead to a better fit of the image. It is also suggested that these points be selected in areas of relatively flat terrain using features such as roads, and rivers as matching features.
SEE ALSO
DIFF/GEO offset parameter file,
create_diff_par, and offset_list_fitm.