Digital Comparison and Correlation Techniques of Remote Sensing Images With Differing Spatial Resolution

Some digital techniques are proposed to compare and correlate remote sensing images having different spatial resolution. To compare high space resolution images with other images having lower resolution, a procedure is presented based on the use of a suitable low-pass digital filtering applied to the high resolution image and subsequent data reduction to obtain an image comparable with the lower resolution one. To pass from low space resolution images to higher resolution ones, two "estimation" techniques are proposed: spectral extrapolation performed on the space frequency spectrum of the low resolution image; approximated Shannon interpolation performed on the low resolution image, followed by "re-sampling" procedure. Some practical examples are given, regarding Landsat and Seasat images.