Tasks

Important
  • Try this without AI first - struggle builds understanding.
  • Ask if you are struggling. Asking builds understanding as well!

Task 1

The following command returns the path to a tif file on your hard drive:

system.file("ex/elev.tif", package="terra")

Use this path to import the tif file using rast(), store it as r.

Sample Solution 
library(terra)
r <- system.file("ex/elev.tif", package="terra") |> 
  rast()

Task 2

Explore this object:

  • Determine the minimum and maximum elevation values
  • Make a static map using base plot and tmap
  • Make an interactive map using tmap (tmap_mode("view"))
  • Using tmap, explore different styles and palettes.
Sample Solution 
# Simply looking at the metadata will show min/max values
r
class       : SpatRaster 
size        : 90, 95, 1  (nrow, ncol, nlyr)
resolution  : 0.008333333, 0.008333333  (x, y)
extent      : 5.741667, 6.533333, 49.44167, 50.19167  (xmin, xmax, ymin, ymax)
coord. ref. : lon/lat WGS 84 (EPSG:4326) 
source      : elev.tif 
name        : elevation 
min value   :       141 
max value   :       547
Sample Solution 
library(tmap)

tm_shape(r) +
  tm_raster()

Task 3

The following command returns the path to a tif file on your hard drive:

system.file("tif/L7_ETMs.tif",package = "stars")

Use this path to import the tif file using rast(), store it as l7.

Sample Solution 
l7 <- system.file("tif/L7_ETMs.tif",package = "stars") |> 
  rast()

Task 4

Explore this object:

  • Spot the differences to the object r
  • Plot the available layers individually
  • Rename the layers to: c("B", "G", "R", "NIR", "SWIR", "MIR") (see here)

Task 5

Select the Red Green and Blue bands to create a true color map (plotRGB and tm_rgb)

Sample Solution 
names(l7) <- c("B", "G", "R", "NIR", "SWIR", "MIR")

Task 6

Select the NIR, Green and Blue bands to create a false color composite

  • Allow 15-20 minutes for these exercises
  • Help students with band selection syntax - this is often confusing initially
  • Encourage experimentation with different band combinations
  • Point out how vegetation appears differently in true vs false color
  • This hands-on experience reinforces the theoretical concepts
Sample Solution 
tm_shape(l7[[c("NIR","G","B")]]) + tm_rgb()