Data for the emigration map project was – except for the genealogical data – all from public sources. Interestingly enough there is also a relative wealth of sources with relevant historical GIS data.
- Genealogical data from Swiss Buehrer Web Site as of October 2011 (http://www.myheritage.de/site-72226521/swiss-buehrer). For practical reasons (notably less work for georeferencing) all persons not linked to the main family tree were removed as well as substantial irrelevant side lines like the Finney emigration from Ireland.
- Digital Elevation Model DEM (30” resolution) from U.S. Geological Survey (ftp://email@example.com/data/gtopo30/global/) provided the base for the fairly easy looking smoothed hillshade layer that proved to be the most difficult to produce.
The four 30” DEM tiles delimited by longitude/latitude (W140N90, W140N40, W100N90 and W100N40) that cover the United States were merged into a single DEM file which was subsequently reprojected and downsampled, all in QGIS.
In GRASS a moving average was applied to the DEM which was exported as a GeoTIFF. From there, gdaldem was used to generate a hillshade GeoTIFF that received final blurring in Photoshop. Anything but easy.
- Physical features (1:10 million scale) ocean, coastline, land, rivers and lakes from Natural Earth (http://www.naturalearthdata.com/downloads/)
- US counties from the US Census Bureau (https://www.census.gov/geo/maps-data/data/cbf/cbf_counties.html)
- Historical state boundaries (filtered as of 1870) from the Atlas of Historical County Boundaries Project (http://publications.newberry.org/ahcbp/index.html)
- Historical US railroads (1870) from the Railroads and the Making of Modern America Project (http://railroads.unl.edu/resources/)
- Historical US census data (1870) from the National Historical Geographic Information System NHGIS of the Minnesota Population Center (https://data2.nhgis.org/downloads). The custom download data included e.g. the number of Swiss-born citizens per county and other interesting data that was not yet used in the project.