Mod 4: Spatial Enhancement, Multispectral Data, and Band Indices

This week we dove into the deep end of trying to find features based on feature descriptions or clues in pixel data given to us. By using what I learned in the lectures and lab exercise I was able to locate the 3 descriptions In ERDAS Imagine by either examining the histogram, visually examining the image as a grayscale or multispectral, and using the inquire cursor to find brightness values. Below are 3 maps showcasing the features for each of the 3 descriptions (clues) I was given to find.

This map above shows that water is the feature causing the Layer_4 spike between pixel values of 12 and 18. I found it by looking at the tm_00.img as a grayscale and looking for the darkest features because the spikes between the pixel values of 12 and 18 were on the left side of the graph. As we learned spikes on the left indicate dark in that band, so I concluded it must be the water by visual and the inquire cursor steps. I chose to display the feature in a False Color IR (R=4, G=3, B=2) because the red to black color made it stand out the best.

The map above shows that snow/ice is the feature that a. causes a small spike in layers 1-4 around pixel value 200, and b. a large spike between pixel values 9 and 11 in layer_5 and layer_6. I found snow and ice by looking for something bright because of the pixel value of 200 at the true color tm_00.img and the snow covered mountains were definitely the brightest. Then with the panchromatic image in another pane I could look there to see layers 5 and 6 pixel spike values 9 and 11, and I knew I was looking for something dark. The snow/ice covered areas met both the a. and b. criteria we were looking for. I chose the False Natural Color (R=5, G=4, B=3) to display them because it made the feature stand out in a bright baby blue color.

The map above shows that shallow and deep water is the feature causing certain areas of water in layers 1-3 to be brighter, layer 4 becomes somewhat brighter, and layers 5-6 remain unchanges. This area shows that variation in water. The hint was already there that we were looking for variations in water, so I experimented with different band combinations and looked near land where I knew I might see variations. (The Navy sailor in me was helpful as well, but that’s just my own experience being useful I think) Sure enough I could tell where shallow water was and where the darker deep water was, so those are the only water variations that I could tell and I feel like my hunch was correct here. I ended up using a R=3, G=2, B=1 band combination because that was the clearest to me. Overall, this was a tedious and difficult task. I tried to make it sound simple above, but there was so much confusion and fumbling between the lab and book pages on my end. Hopefully it was a success, but I do have some unease about this topic still.