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ChangeMatters- Landsat made easy



[Source: ESRI; ChangeMatters. Location: Ontario, CA]


Back in May, ESRI released a very accessible, intuitive online Landsat imagery viewer that turns out to be quite useful for the first stages of analysis; or, conversely, as a check on GIS results. ChangeMatters utilizes three adjacent image viewers; as you toggle through image capture dates, location and distance in one window, the others two windows snap-to in formation. The third viewer serves up the NDVI (Normalized Difference Vegetation Index) that displays increase/decrease in vegetation per location.



[Source: ESRI; ChangeMatters. Location- Las Vegas, Nevada]


This viewer is one of several that ESRI has recently launched. Its hard to detect the exact audience of these viewers; I suspect its ESRI’s way to drum up general interest as these are not really serious GIS analysis tools as much as they are topical, accessible viewers. But they are very nice as educational opportunities, and they are a decent way to gain a ‘quick take’ on land use change since 1975, an early date in the Landsat program.

As seen in the following legend, ChangMatters leaves the first two Landsat images alone, while serving the result of the NDVI calculation in the third viewer window. Breaking vegetation cover down to a Increase/Decrease binary produces some interesting results. As seen in the Las Vegas example above, what we would assume is a decrease in land use value for vegetation is actually an increase: desert sands become irrigated subdivisions. In using the viewer across different geographies, it becomes evident that it works best in cases of natural disasters- volcanoes, fires, ect. where vegetation cover changes very rapidly; or where urban and suburban sprawl quickly overtook natural landscapes, particularly during to the early 2000s housing boom.



[Source: ESRI; ChangeMatters]



[Source: ESRI; ChangeMatters. Location- Tegucigalpa, Honduras]

 

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