Instructions on using the 1930-1940 web GIS system
- This system opens up to a map of the U.S. The first step is to open the menu in the upper left corner with this icon:
- Now select one of the available cities from the menu, choose a variable to display, and use the slider to select either 1930 or 1940.
- By default you will see a ward map of the city in 1930 with a historically accurate street grid. There are three toggles: switch between the ward map and the enumeration district (ED) map, switch to turn on or off the historical street basemap layer, and switch to turn on or off the contemporary basemap layer. When both basemap layers are on, the map shows historical streets within the city and contemporary streets and highways outside the city.
- Click on a polygon feature within the city to see data for that ward or ED.
- The opacity of the visible layer can be adjusted. At around 0.5, you can see the colors of the thematic map and also the street grid beneath it.
- The system also has options to show different contemporary basemaps (upper right corner). There is a collection of 24 basemaps with different themes (e.g., street maps, topo maps).
- When you have created the desired map and zoomed into the area you wish to display, you can “Print” a copy for use in other applications. You have options to customize the tile, format, scale, legend and other layout elements. Note that the printing service may have a delay of up to 30 seconds if you request to show the whole layout. When the printout is ready, the name will appear at the bottom of the box under “Exported files.” Click on it to save.
- The system also includes functions to select an area within the city (Select) for the purpose of downloading data. Three drawing options are provided, that is, select by a polygon , select by a rectangle , and select by a circle . Once a selecting geometry is drawn, you can refine your selection through the “Transform” tool and “Reshape” tool . The “Transform” tool reshapes or moves the bounding box that contains your selected area, and any part of that area outside of the new bounding box will be omitted. The “Reshape” tool allows you to edit vertices of the selected area. Then click anywhere outside the selected area and the revised selection will be updated instantly. In addition, the “Undo” and “Redo” tools can be of help in the editing process. You can select only one area at a time.
- The “Download” function provides data for your selected area. The download is a CSV file including the ward or ED number and population data for all the units within the selected area.