Week 3 - Raster data

For our third week, we will learn about the second most common data model for spatial data: raster files. While vectors are good at representing separated and/or well-defined individual regions, rasters excel at representing gradual, continuous data such as surface temperatures or elevations.

ILOs covered

  1. Understand the structure of spatial data and choose appropriate data types and models for storing and representing it;

  2. Obtain and assess the quality of spatial data from online and offline sources and produce new spatial data using computer and field methods;

  3. Create map visualisations that adhere to cartographic principles and can be easily and unambiguously interpreted by the non-specialist public;

  4. Plan and execute GIS analytical steps to solve spatial problems successfully;

What will you learn

For every week, we will list the main theoretical and practical learning goals. Use these as a ‘checklist’ to gauge your learning for each week. If you don’t feel confident you have learned any specific topic, then revisit the week’s material!

Theoretical knowledge for Week 3:

  • What is the raster data model?
    • How are rasters represented?
  • What are the components of a raster file (rows, columns, bands/channels, resolution)?
  • What are the main raster file formats?
  • What data types can rasters represent?
  • What kinds of data can we represent using raster data?
  • Raster / vector component equivalence
  • Raster / vector tool equivalence
    • No concept of ‘ selection’
  • What kinds of questions can we answer using rasters?
  • How can we transform rasters to vectors and vice-versa
    • The concept of raster resampling
    • The concept of raster contrast manipulation

Practical knowledge:

5  Lab 5: Working with raster data

  • How to identify raster files
  • How to load raster files
  • How to get raster properties
  • How to reproject raster data
  • How to mask rasters
  • How to set raster symbology
    • Continuous variables
    • Categorical variables
  • How to use the identify tool to get raster information on the fly
  • Working with Digital Elevation Models
    • Calculating slope, aspect and viewshed

6  Lab 6: The raster calculator and other rastery bits

  • How to calculate raster statistics
  • How to ‘select’ using the raster calculator
    • Boolean operators on the same band
    • Boolean operators between bands
    • Band arithmetic
    • Making flowcharts
  • Mosaicking rasters
  • How to adjust the stretch of a raster
  • Styling raster Images
  • Resampling methods