This was another exercise I spent way more time than I should have on. I am definitely a “hands-on” learner and while the concepts in the book make sense, it’s not until I’m in the lab and using the tools myself that it really begins to come together for me. This week we learned different spatial enhancement methods and how they could be performed in both ERDAS Imagine and ArcGIS Pro. All was going well until the map making portion of the lab. I could not figure out why my band combinations were not transferring over between programs, I would set it to False Color and it would open looking completely different in ArcGIS. Since the Intro to GIS course focused mostly on vector data and I had no experience with GIS before this program the raster data has been a bit problematic for me. So often I go to adjust my image in some way and have no clue how to do it. I often can find a work around but usually there is an even better option or my option would cause another issue to arise. I probably should’ve just asked my question and waited but I know if I can find a solution myself it usually sticks more and I often learn a lot of other stuff in the process so after almost an hour of trying all different methods of saving and opening my documents (I probably created 15 or so files trying to save in all different forms), the only one that worked was jpeg. I could have used a jpeg but it doesn’t come with the raster data and isn’t as clear of an image as the .img or .tiff files. I had the idea to type “false color” into the tools and used the create color composite tool that popped up to adjust my bands. This gave me the desired effect- a false color image, but what I didn’t realize until I brought it up in office hours was that this completely reassigned the bands, so what was band 4 was not just displaying as band 1- it became band 1. This means that had I continued to use this method of altering the colors, each photo I made would have the same band combination as I re-assigned the layers: Red: B1; Green:B2; and Blue:B3, and it wouldn’t have been clear which band from Landsat 5 I was actually using. Fortunately, as the professor showed me, I was able to rectify this by using the original file and simply changing which bands were displayed using the “Raster Layer” tab. A much simpler solution to my problem and something I will now definitely remember how to do going forward!
Anyway, I was finally able to create my maps which were of 3
unnamed features in an image of a mountain range in Washington State. We were
given tips to identify these features using some of this weeks new skillsets.
I identified the first feature as water and chose to display
the river in a false color photo because it really brings out the distinction
between the water and the vegetation.
The second feature I identified was the snow on top of the
mountains. I had to do some digging to figure out how to best display this
feature. I almost went with true color but read that clouds and snow were
indistinguishable in this band combination. I also knew band 5 and 6 had large
pixel spikes in this region so I thought to incorporate them somehow. I found
lots of information about how short wave infrared (band 5) is useful for
distinguishing snow from clouds but I wasn’t sure where to put it and what
bands to use with it for my combination. I found a research paper on Landsat 5
and glacier analysis that said the 5-4-3 combination was useful for studying
glaciers so I tried it. The clouds were a pinkish hue while the snow was
clearly blue with this combination so it was my ultimate choice.
Finally, the 3rd feature was to show variation in
brightness in the water throughout the map. I chose true color because it is
best for viewing aquatic environments.
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