Week 1: Discussion Section

Making maps with tmap and beyond

Author

Alessandra Vidal Meza

Published

September 27, 2024

Reference

Refer to the Plotting Geospatial Data resource and tmap book to help get you started.

Learning Objectives

  • Read in spatial objects
  • Create map with single spatial object
  • Create map with multiple spatial objects
  • Use different types of tmap plotting formats (e.g. tm_polygons(), tm_fill(), tm_dots(), etc.)
  • Adjust color palettes
  • Include essential map elements (e.g. scale bar & north arrow or graticules)
  • Create an interactive map
  • Bonus Challenge: Reproduce map using ggplot2 instead of tmap

Get Started

Let’s load the necessary packages:

library(here)
library(tidyverse)
library(stars)
library(sf)
library(tmap)

And read in the spatial objects for Easter Island (Rapa Nui/Isla de Pascua):

  • ei_points: file contains several points on the island
  • ei_elev: raster with elevation data
  • ei_borders: polygon with the island outline
  • ei_roads: lines contains a road network for the island
ei_points <- sf::read_sf(here::here("data", "week1", "easter_island", "ei_points.gpkg"))
volcanoes <- subset(ei_points, type == "volcano")
ei_elev <- stars::read_stars(here::here("data", "week1", "easter_island", "ei_elev.tif"))
ei_borders <- sf::read_sf(here::here("data", "week1", "easter_island", "ei_border.gpkg"))
ei_roads <- sf::read_sf(here::here("data", "week1", "easter_island", "ei_roads.gpkg"))

Now, to meet our learning objectives, your task:

  1. Create a map of Easter Island
  2. Create a map of Easter Island and…
  • …denote the island’s borders and continuous elevation
  • …denote the island’s volcanoes and roads
  • …play with the color palette and essential map elements
  1. Create an interactive map of Easter Island