Module 9 - Flowline Mapping

Flow Maps are another type of thematic maps. They are used to depict the movement of phenomena between geographic locations, typically using lines of varying widths for quantitative data, or for qualitative data. There are several types of flow maps, such as distributive, radial, network, continuous, and telecommunication. Not only is it important to select appropriate data to be displayed as a flow map, but it is also essential to apply specific design decisions when creating flow maps because issues may arise. Two very important design principles when working with flow maps include: 1. "Flow lines are highest in intellectual [importance] and therefore highest in visual/graphic importance", and 2. "Smaller flow lines should appear on top of larger flow lines" (Borden Dent).

For this week's lab assignment, we solely utilized Adobe Illustrator to create and design a distributive flow map portraying immigration populations to the United States by country of birth from 6 world continents in the year 2007. In my map, I displayed this information by using flow lines of proportional thickness to the number of immigrants. Using the data (which is derived from the U.S. Department of Homeland Security Office of Immigration Statistics), I calculated the width of my flow lines by first calculating the square root of immigrants per continent; then I applied the following formula to get my line weight by proportion: width of line symbol = (maximum line width) x (SQRT value/SQRT maximum value).

Additionally, my final map product also displays a choropleth inset map of the United States showing percentage of total immigrants per state, using a Natural Breaks data classification method. The inset map uses the North American Lambert Conformal Conic projection which maintains the shape of features pretty well. On the other hand, the main frame map uses the Winkel Tripel projection, compromising a little bit of everything (distortion of shape, area, distance, and direction)--making it a popular option to display world maps.

I used a lot of new Adobe Illustrator tools to create this map. Additionally, I applied a few stylistic effects to enhance the geographic content. It's important to capture people's visual attention first, with the goal to later on attract them to the actual spatial information being displayed. Therefore, I used drop shadows all around the continent polygons and the continents' text names. I decided to use a white background instead of an ocean blue to make the bright colors of the continents pop (I feel this gives this map a fun appeal). Applying these stylistic effects helped my map establish figure-ground. The flow lines are the darkest features in my map, the main focus, which I did on purpose to achieve visual hierarchy. And finally, I made sure to lighten up the outlines of the countries and the titles and legends with the use of transparency to help the audience focus on what's important.