GIS 4035 Module 6: Spatial Enhancement

Landsat 7 image run through Fourier transformations, sharpening, and statistical filter in ERDAS Imagine.

Past modules in this and other courses have mentioned that GIS operators often must correct acquired imagery for various errors prior to using it for their analyses. This module introduced us to some of the ways such corrections can be done. We explored the tools available in both ERDAS Imagine and ArcMap, including Fourier transformations, high pass filters and low pass filters. Low pass filters generate output that appear smoother and less detailed than the original image; noise in the image is also removed, according to the size of the kernel chosen. High pass filters create high contrast and noisy output that highlights the edges of features.

For the assignment, we were to experiment with Imagine and ArcMap to create an enhanced version of a Landsat 7 image that minimizes as much as possible the scan line corrector failure striping without removing too much detail. The assignment walked us through using the Fourier Transform Editor tool as the initial step in the process. While I experimented with different wedge placements in the editor, I was unable to create an image that was significantly better than my first attempt. After experimenting with various filters and settings in Imagine and ArcMap, the final image used above was the result of sharpening and a statistical filter in Imagine. Other filter and setting combinations created images similar to this, and a few were significantly worse. I did not experiment much with the histogram, however; I hope to learn more about histogram manipulation in future modules.