For the deliverable assignment I
scanned both composite images from the lab to look for unique areas of interest. Ultimately, I chose to use the composite image of
Northwest Florida as I am more familiar with that area. I opened two views in ERDAS with a grey scale
band 6 image and a multispectral image of the same location. I adjusted the breakpoints of the gray scale
histogram by using the Discrete DRA button.
This removed the “whitewash” appearance of the image and made features
appear more distinctly by providing more contrast. I chose to change the band combination of the
multispectral image to be a false natural color or Thermal IR composite of 647
as we used in the lab Exercise 3.
After beginning with the setup described above, I began to scan the synced images. I honestly used size, shape, and texture to notice my area of interest. It appeared very bright in both images but had a distinct, unusual shape that was highlighted in the multispectral image. The overall feature was a square shape that had a Star of David like symbol in the center of the feature square. The symbol in the center was a square with a rotated 45° square on top. The details of this feature could not be seen in the gray scale image. I began displaying the image in various multispectral bands to see which band combination could display the feature the best. Ultimately, the RGB 742 band combination made the feature stand out the most from its surroundings. I used the Portland State University webpage (PDX) mentioned in the lecture to help me understand how this combination could provide more detail about the feature. Urban areas in this band combination appear in different shades of magenta. The symbol at the center of this feature area had two distinct shades of magenta. The shape of the feature and width of the sides of the square and diamond comprising the center symbol resembled that of an airport runway. I was confused by the shape of the symbol as most runways appear as an X or cross or as parallel long lines. The PDX website described differences of reflectance responses depending on the terrain feature. If this feature was a runway the square and the diamond may appear as different shades of magenta because one is concrete and the other is asphalt. Another explanation for the color shade difference could be the age of the terrain feature. Maybe the square and diamond are the same material but one was resurfaced or is older than the other surface. To confirm my suspicion that this was some type of airport I used Google Earth. The feature is a Naval Outlying Field that is used for helicopter training which explained the difference in the runway layout versus a traditional airport.
After beginning with the setup described above, I began to scan the synced images. I honestly used size, shape, and texture to notice my area of interest. It appeared very bright in both images but had a distinct, unusual shape that was highlighted in the multispectral image. The overall feature was a square shape that had a Star of David like symbol in the center of the feature square. The symbol in the center was a square with a rotated 45° square on top. The details of this feature could not be seen in the gray scale image. I began displaying the image in various multispectral bands to see which band combination could display the feature the best. Ultimately, the RGB 742 band combination made the feature stand out the most from its surroundings. I used the Portland State University webpage (PDX) mentioned in the lecture to help me understand how this combination could provide more detail about the feature. Urban areas in this band combination appear in different shades of magenta. The symbol at the center of this feature area had two distinct shades of magenta. The shape of the feature and width of the sides of the square and diamond comprising the center symbol resembled that of an airport runway. I was confused by the shape of the symbol as most runways appear as an X or cross or as parallel long lines. The PDX website described differences of reflectance responses depending on the terrain feature. If this feature was a runway the square and the diamond may appear as different shades of magenta because one is concrete and the other is asphalt. Another explanation for the color shade difference could be the age of the terrain feature. Maybe the square and diamond are the same material but one was resurfaced or is older than the other surface. To confirm my suspicion that this was some type of airport I used Google Earth. The feature is a Naval Outlying Field that is used for helicopter training which explained the difference in the runway layout versus a traditional airport.
I
feel less sure of my understanding of the relationship between bands and layers
and how to know which band combination is covering what wavelengths. I think some of my confusion is related to
semantics and the interchanging of the words bands and layers.
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| Spencer Naval Outlying Field Used For Helicopter Training Displayed Best in R-7, G-4, B-2 Band Combination |
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