7 Mapping

pdf version

GIS

GIS – Geographic Information Systems – is a massive field; we’re just scratching the surface here.

But it’s possible to actually create real maps that no one has made before pretty easily by drawing together elements from various map layers online.

Key terms

  • Map Data formats
    • Raster: image files: points with colors but without semantics
    • Vector: files of lines; not as pretty but capable of handling data.
  • Projections

GIS Software

ArcGIS

The industry standard is ArcGIS, made by the company ESRI. It’s expensive! That’s about the only downside. If you take a GIS class, they usually use Arc.

QGIS

QGIS is free, and not all that bad. We’re using it so you get used to something you’ll be able to keep using without a site license.

Web mapping

There are a variety of web mapping technologies that are taking different areas of the humanities and journalism by storm. Hypercities builds on some of the Google platform; Stanford/Orbis builds on D3.js, which is hard to use (requires coding in Javascript) but extremely powerful for interactive maps. It’s what, most notably, any map you’ve seen on the New York Times in the last few years uses.

Finding Map Layers

Working with layers

Right click on a layer to examine it. The two most important options are:

  • Attribute table, which lets you see and sometimes edit the data about each item in a vector layer, and
  • Properties, which lets you change the appearance of a layer: map cities by population density, for instance.

Georectification

Georectification is the process of warping a map so that it can be used

Some examples of various sorts:

Abby Mullen has posted a list of instructions for georectification online

Geolocation

The process of matching places to points on the map.