Hi class,
This week I’m going to show you a few tools that you many not have seen before. First, go to the Change Matters page at ESRI. This site let’s you pick anywhere in the world and look at various images (color infrared, enhanced vegetation, etc.) from 1975, 1990, 2000 and 2010. It also displays a change image for the chosen years. For those of you that are studying change, this is a good way to see what you might be looking for, and better understand some of the methods for detecting change. It is also very fast, compared to downloading data for yourself.
One reason this works is the data set being used: the Landsat Global Land Survey (GLS). These are orthorectified, and terrain corrected images, so they overlay each other quite well, and they are worldwide for the four years mentioned above. If you have downloaded an image that is not lining up correctly with your ground truth, then you might think about using a GLS image to help you shift or georectify your image.
Lab this week will cover several Spatial Analyst techniques for working with images, including masking, using the con() and setnull() statements to eliminate unsightly excess zeros, and split images apart or paste them back together. The lab outline is here:
https://udrive.oit.umass.edu/xythoswfs/webui/_xy-11907615_1-t_n5PyBTwQ
Jack