Monday, July 20, 2015

July 20: Week Three!

I spent today by picking up where I left off on Friday: creating masks in ENVI.  I needed to create a mask to cover/ignore all of the distortions caused by the broken mirror in Landsat eight.  Basically, the broken mirror caused lines to form on the images, and instead of actually collecting data, these lines all show zero as the data.  Since the data that would be underneath these lines does not have a value of zero, having incorrect data when running indices would effect averages, means, and other calculations which would throw off the entire project.  So, I spent the morning surfing the web and the ENVI help page in order to figure out how to apply a mask.  I thought that I could simply tell the software to ignore data values of zero (the obscuring lines), and then a mask would be created quite simply.  Unfortunately, the software only allowed me to input a range of numbers, which was not helpful considering that I only wanted to mask one numerical value.  After a morning with very little luck, I went to Dr. Vodacek to ask him what I should do.  He reasoned that creating and saving a region of interest (RIO) would be the best way to do it.  To create a region of interest, I have to click every line individually and then save the RIOs as one file.  I wish that there were a way to just compute a numerical value to ignore, because clicking each line can be a bit painstaking and takes a lot more time.  However, at least now I have a way to mask inaccurate numbers which gives me access to many more images that would otherwise be obscured.

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