This week's focus revolved around multispectral analysis through spectral enhancement. Essentially this means to take existing spectral data and present it in a manner that might bring out certain relationships or patterns not readily present in other presentations. The main objective for this assignment was to study an image set and identify certain spectral relationships that aren't readily seen looking at a standard true color image. This is accomplished by manipulating the pixel values to show other relationships through gray scale panchromatic views of single spectral bands or different combinations of multiple bands such as that seen from a standard false color infrared image. Both ERDAS Imagine and ArcMap were used to explore the image provided. Several tools within ERDAS were used, such as the Inquire Cursor to look at particular groups of pixels for their relevant brightness information. Histograms and contrast information were utilized to identify patterns within multispectral and panchromatic views of one or more spectral bands. The image shown in all three maps below was provided by UWF. This week's assignment required us to identify three different sets of unique spectral characteristics present within the image and to build maps displaying our results. These results are shown below.
The first criteria involved locating the feature in spectral band 4 that correlates to a histogram spike in value between 12 and 18. Band 4 is generally associated with near infrared (NIR) energy and is good for looking at vegetation and soil and crop land and water contrasting. With this task, I needed to look at the histogram and find the resulting spike, which is shown in the lower right of the image displayed below. From there, I specifically made this the only “visible” feature in the map. Both images shown on the left are using band 4, which proves that the water does stand out quite significantly.
The second criteria involved locating a feature that represents both a spike in the visual and NIR bands with a value around 200, and a large spike in the infrared layers of bands 5 and 6 around pixel values 9 to 11. The main features of this image are displayed in a false natural color employing bands 5, 4, 3. This combination of colors does particularly well at letting the areas that are being inquired about be displayed. I’ve also created insets to display the different extents of the same data in different spectral scenes. The two separate breakdowns of pixels of value 200 in visual bands and values 9-11 in the infrared bands are compared on the lower right.
The third, and final, criteria revolves around water features in
which viewing bands 1-3 become brighter than usual, but remain relatively
constant in bands 5 and 6. A true, or natural color, image is shown on the upper right. Looking at this image, you can see a river in the upper right portion that is much darker than the water ways featured in the other images. The image shown adjacent to the natural color photo is a custom combination of bands 6, 3, 2 to focus
the brightening of the inlet/bay feature while not pronouncing the IR energy in
the same ways as the typical false color IR, which is shown in the lower right corner. Extent indicators were used to show
the different looks at the specified band and pixel value combinations
identified. A gray scale image was
created to reflect band 3 which shows the largest brightening values.
This assignment wasn't easy, since it involves many concepts I'm still trying to understand. However, I feel as though I've learned some new things throughout this week's assignment. I'm looking forward to learning more throughout the remainder of the semester.
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