Module 9: Flow Mapping

This week the focus was Flow Mapping.  The flow map created in lab this week is a radial flow map, all the spokes (geographic regions) feeding into a centralized hub (U.S.)  There are two other  types of flow maps Parks considered:  a network map shows connectivity of multiple locations (airline route map) and finally distributive map shows flow of  data between geographic regions.  There are two main subcategories of distributive flow maps:  one shows the entire world and attempts to depict actual routes of flow and second depicts flow within a land mass and precision is not as important as general direction and magnitude.  There are also two types of flow maps the text explains that Parks did not consider:  Continuous flow maps, which depict movement of continuous phenomenon such as wind or ocean currents and Telecommunication flow maps, that Parks considered network maps.  The data for this map is quantitative, however, flow maps can be used for qualitative data as well.  The flow lines utilized stylized placement to show spatial interactions as opposed to a specific route from geographic regions to the U.S.  Borden Dent provided essential design decisions in creating flow maps:  flow lines should be depicted as the highest in visual / graphic importance, if flow lines cross smaller flow lines should appear on top of larger, arrow heads are important if flow directions is important, land and water contrast are essential, projection is important, keep it simple, legends clear.  I utilized these guidelines in this map.  The flow lines are the most stylized element in the map keeping it at the top of the visual hierarchy, my flow lines do not cross, arrow heads are included and directional, definite land water contrast, Winkel Tripel projection (compromise projection, relatively minimized distortion of shape, area, distance, and direction, although none of these is really preserved), design is simple, and only the choropleth legend was included as the flow lines are labeled with the actual numeric representation.  The proportional line widths of the flow lines were calculated in excel per the lab instructions.  I chose to indicate that the map was not to scale as opposed to trying to show two scales for seperate elements of the map.  I changed the color of the continental U.S. to white to infer the enlargement of the choropleth in the middle.  I left Alaska in it's location and changed the color to correspond with the data for the choropleth map.  I did enlarge and include Hawaii separately.  I decided to not follow the same orientation for Alaska and Hawaii because Hawaii had to be enlarged to be seen, but Alaska took up too much space if enlarged at the same rate.