Lab 06 - Spatial Enhancement

Lab 06 introduced us to using tools in ERDAS and ArcMap to enhance remote sensing data. We practiced downloading and formatting data from the USGS Landsat Archive, used high and low pass filters in ERDAS on the ETM+ band 8 of a panchromatic layer of a raster, used the Focal Statistics tool in ArcMap for range and mean values, and finally experimented with removing stripes from and enhancing a Landsat 7 image.

The lab walked me through some initial enhancement steps including using the Wedge Mask and Low Pass Filter in the Fourier Transform Editor and 3x3 Sharpen kernel setting in the Convolution tool. This reduced the dark black value of the stripes, smoothed out the image and stripes, and then added some feature sharpness back in. These results were fair, but our goal was to improve the overall quality further if we could. So from there I spent some time trying different enhancements using the Radiometery Adjustments, Brightness and Contrast, Histograms, and Convolution kernel settings. I also went back into the Fourier Transform Editor and tried different Wedge and Low Pass Filter increments to see if I liked any of them better.

In the end, I settled on using only the Wedge Mask in ERDAS and then changing up the histogram in ArcMap to get a file I think works pretty well. I adjusted the Stretch Type by Standard Deviation, default of n at 2.5, and gamma stretch at 0.75. This combination of tools reduced the stripes, kept the sharpness of the features from the original image, and adjusted the contrast to help increase the ability to separate the light, dark, and mid-tone values of features.

Map showing Landsat 7 image before and after photo enhancements in ERDAS and ArcMap.