Projections, Extent, and Resolution
Content for Wednesday, September 17, 2025
Congratulations, You’ve loaded your first spatial data into R!! Now we’re going to start learning how to access and manipulate the 3 fundamental properties of spatial data: coordinates/geometries, extent, and resolution. We’ll spend some time talking about why these things matter, both philosophically and operationally. Then learn how to use sf and terra to access and manipulate these attributes.
Readings
Setting the Stage
Scale and Projections by Matson et al. provides an accessible overview to what projections are and why we need them.
Lying With Maps by Nelson et al. provides a nice introduction to the ways that the representation of spatial data can be misleading.
Technical Details
Chapter 2 from Moraga (2023) provides more explanation projections, coordinates, etc. and their representation in R.
The introductory vignette for the
sfpackage has a lot of useful info onsfobjects and conventions.Section 2.2 on Vector Data and Sections 5.1-5.3 on Geographic Operations in Lovelace et al. (Lovelace et al. 2019) - for more details about vectors and geometric operations on vectors.
Chapter 2, Sections 1-3 and Chapter 3, Section 1 of Spatial Data Science by Edzer Pebesma and Roger Bivand (of the
sf,sp,rgeos, andrgdalpackages)
Objectives
By the end of today, you should be able to:
Describe a Coordinate Reference System and why they matter.
Understand what a projection is, the constraints of projections, and how we navigate them in
RLink concepts of scale to measurements like extent and resolution
Access the projection, extent, and resolution using
R
Slides
The slides for today’s lesson are available online as an HTML file. Use the buttons below to open the slides either as an interactive website or as a static PDF (for printing or storing for later). You can also click in the slides below and navigate through them with your left and right arrow keys.