Key Points

Exercises: Acquiring Raster Data using Imagery Databases

  • Scanned historical maps are widely available online but usually require georeferencing before use in a GIS.
  • CORONA imagery (1960–1972) provides high-resolution historical views and is free from CAST (georeferenced) or EarthExplorer (raw).
  • Sentinel-2 provides free, 10 m resolution multispectral imagery with a ~5-day revisit cycle.
  • SRTM DEM tiles provide 30 m elevation data that can be used for terrain analysis in the next session.

Exercises: DEM Analysis and Visualization in QGIS

  • DEMs should be reprojected to a metric coordinate system (such as UTM) before performing terrain analysis.
  • Slope, aspect, and hillshade are derived layers that each reveal different characteristics of the terrain.
  • Pseudocolor symbology with classified elevation ranges makes DEM data far more readable than the default grayscale.