Working with Shapefiles and Georeferencing Historic Maps

Now that you have elections data in an Excel spreadsheet, we start the process of making the shapefiles that make the maps. The first step is to get a shapefile of county boundaries and to georeference a scanned map of VA Congressional districts. This will give us the ability to use an image file (a jpeg) to help create the shapefiles. You should have a copy of ArcGIS available to work with, as well as a web browser (this tutorial uses ArcGIS 9.3). The shapefiles in this tutorial series come from publicly available sources, especially TIGER line data. However, there are many more resources available with some searching on the web. Feel free to pause or back up during the course of the video tutorial as necessary. Clicking through to the Vimeo site will allow you to see the video more clearly.

Shapefiles and ArcMap Georeferencing from LaDale Winling on Vimeo.

There are many different projection systems, and this is a potential sticking point if you work with shapefiles from different sources — one may put the state of Virginia in a whole different place from another, while a third might have it in a similar place, but stretch it into a different shape. It is possible to change from one projection to another using a Data Management Tool from the Toolbox (“Project”), and there should be helpful books available at your institution, such as Understanding Map Projections by Melita Kennedy and Steve Kopp.