Constraint based on the values in the area of overlapping frames

To enhance the referencing method a program was developed to include the constraint that differences between brightness-corrected values in areas of scene overlap are minimised. The software has been written to iteratively reduce the scene brightness variation between two target frames. It systematically cycles through various referencing technique parameters in order to reduce the spectral difference in the scene overlap. This is achieved by proceeding through the following steps of the referencing technique:

• Re-scale the reference image to the data range of the target imagery. Subtract the re-scaled reference imagery from the target imagery and transform the resultant residual image to the fourier domain;
• Apply a low pass filter to fourier images
• Transform the filtered fourier images to the spatial domain and subtract from original target imagery, thereby reducing the effect of scene brightness variation.

To minimise the difference in scene overlap the following step has been added to the program:

• Determine whether the level of correction falls within acceptable limits by determining mean values for user specified regions within the scene overlap of the corrected target imagery; and,
• If the level of correction is inappropriate, repeat algorithm from step 2 increasing the size of the low pass filter.

The program has been written in IDL