Marginalia

Marginalia provide additional information to promote understanding and reduce confusion in map reading.

What is your point?

Does your title quickly cue the reader to the map’s purpose of theme? Try to avoid writing titles that simply describe the location of your map. Try to write a title that helps people see the meaning of your mapped geography and not just the location of it.

Example: Bill Bunge (1968)

What are your instructions?

What would you like someone to know about your map? What directions should you provide to help your audience read and understand your map? Imagine that you are standing next to your map and you have 15 seconds to talk to the reader before they start looking at your map. Put this information on the map in a place where people will likely see it early. Do this by placement (upper-left is a good place) rather than visual weight. A good map introduction is not that different than a good written introduction. You want to help the reader understand at least three things:

  1. What is this map about?
  2. Why is this important or why should a reader care?
  3. How are you showing them this? (This could include a quick description of dataset, a quick description of how to read or interact with map, or a quick description of your design aesthetic.)

Some cartographers also like to tell the reader what the map shows. Other cartographers simply want the introduction to encourage the reader to spend time with the map and come up with their own interpretations.

Which way is north?

Will the map reader be able to orient the map? If your map follows the ‘north up’ convention of most maps, then you may not need to include a north arrow. However, if north is not up, or if you are showing a geography that may not be familiar to your audience, or if you include reference features that may be confusing (such as the coastline along Santa Barbara, CA where the Pacific Ocean lies to the south of the mainland), then adding a north arrow will likely help the reader orient and reduce confusion.

Reference scale

Is it important for your audience to understand your map’s scale? Do they need to reason about distances? If so, did you include a scale bar or did you label distances directly onto connecting features like roads or did you provide some other means for directly representing the map’s scale? When choosing increments, did you use round numbers with intervals that reflect how people think about distances?

Where in the world

Will your reader know the geographic context of the map? If not, will the reader benefit from knowing this, or can your map function without this geographic context? If you are making a tourist map for tourists who are already at your site, then you probably do not need to include a locator map. But if your audience is not already present in your map, then they may need some help understanding how your map fits the world as they know it.

Sign dictionary

Have you considered which features should be included in a legend or map key and which features you can leave off? In general, reference features often do NOT need to be included in a legend. There are two reasons for this:

  1. They should be styled with iconic principles (e.g. blue for water).
  2. They will often be labeled (placenames).

So the iconic styles and associated place names together function like a legend (helping to define the features directly on the mapped geography).

In general, thematic features should be defined in a legend or map key. Their inclusion helps echo their significance. (Look how important these things are! They got listed in a special place on the map!)

There are a couple of conventions for legend design:

  1. Arrange like a dictionary: symbol on left, definition on right.
  2. Arrange logical groups: you can do this either by geometry (area features, line features, point features shown in groups) or by theme (water features, transportation features, administrative features, etc).

Example: NPS map of Acadia National Park

Sources

Did you list the sources of your data? You should include enough information to help someone find the datasets that you use or know the source material for data that you created. This information should be low in your visual hierarchy: there if people want to find it, but not emphasized.

Credits

Did you list yourself as the author/cartographer of the map? This information is often placed in the same location and with the same visual emphasis as the sources.