4  Week 11 Lab Exercise

In this exercise, you’ll be using the terra and tidyterra packages to transform a raster dataset, sample it, and then visualize it. The data you’ll be using is satellite imagery from an area near Lake Turkana in Kenya (eastTurkana.tif). These data contain four layers: three values that are in the visual spectrum (red, green, and blue), and then one in near-infrared (nir).

• These sensor reflectance values are highly exaggerated so that they can store precise numbers as integers rather than floating point (double) numbers. To convert them to reasonable reflectance values, we need to divide them by 10000.

• Calculate the Normalized Difference Vegetation Index: a measure of vegetation greenness that is used as an indicator of vegetation cover. The equation for this is NDVI = (NIR - RED)/(NIR + RED)

NDVI values below 1 are indicative of cloud cover or water, while values below 0.1 are usually indicative bare earth. When plotting, visualize these using a palette that emphasizes a different values that are greater or less than 0.1.

Include your code in a Quarto document with appropriate headings and descriptive text. Grading criteria are available on Canvas.