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Symbolize multiple line attributes

September 16 2008 | 0 comments
Categories: Cartographic Design, Symbology

I'm working on a bikeway map of our city and would like to include the grade and the bikeway class. I'm having trouble symbolizing 3 classes of bikeway and 2 or 3 classifications of grade on a single map. I split the bikways into 50ft segments to capture grade detail for some of the smaller rolling hills. I tried to symbolize grade using color and used a different line type for the class of bikeways but it was confusing. I ended up using color for the class and only 2 grade ranges using solid and dashed lines. I'm still not happy with the results. I also tried markersymbols on the lines but because of the map scale and the 50ft bikeway sections, it was a mess. I've attached 3 versions of the map, one showing bikeway class, one with just the grade grade and a combo map. Do you have any suggestions on how to communicate the bikeway class and grade on the same map?

Mapping Center Answer:

So, this is a great example in that there's a lot to work with.  First, a big part of why this map isn't working optimally is that the figure ground and visual hierarchy are a bit muddled. The background colors are okay, but the colors for the streets, parks, and labels are too strong and compete with the bikeway information.  I like the bikeways 11x17.pdf best, so I'll make suggestions based on that.

  1. Street colors within the city can be a shade or two lighter gray.  This will allow, particularly the major street labels to be better aligned and not require the halo--which cuts into the bikeways (that forces those labels above the bikeways in your visual hierarchy--which is contrary to the purpose of your map).
  2. Labels for streets can be a light gray instead of black
  3. No need to draw the black outline on the city boundary polygon
  4. Parks are too prominent -- in the HSV color model, lower the saturation and increase the value. -- in terms of visual hierarchy, the parks must be below the roads and well below the bikeways. 
  5. Ditto on the prominence of the lake--which should be labeled if it's got a name.
  6. I would consider labeling the parks with a number and list them off to the side. Right now the yellow halo on the black text makes these labels way too prominent.
  7. I would draw the road symbols on top of the bikeway symbols--even if it meant making the bikeway symbols a little wider.  The issue is that I want to see whether the bikeway is actually on a street or not.

In terms of representing the bikeway Class and grade:

  1. I like the red and orange, but the blue looks too much like a stream--consider a purple that is visually equivalent to the red and orange.  The blue also carries additional meaning relative to red and orange in that it looks safer--which in this case seems to be the exact opposite of the truth.
  2. Representing grade or slope is tricky business.  I think using classes of grade works better--the bikeways-combo.pdf was a good start, though the dashes didn't help me.  Instead, I would not try for a bivariate display. Use the solid lines for class; then have another layer for just grade > 4%. Make the symbol a dotted black line with a 'dot gap gap dot gap gap' pattern, i.e., 2:1 gap to dot size ratio.  This can be narrower than the bikeway symbol, and will leave enough of the underlying information to allow the road and class to be seen. This will also be priminent enough to be seen as important and simplify your legend.


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