To North Arrow or Not to North Arrow

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I started my GIS education back when hand cartography was still a course offered at UCLA.  My early teachers drilled into me the standard of adding a title, north arrow, and scale bar automatically to all maps.  The GIS manager at a place where I first worked was adamant that all maps produced in that GIS group have north arrows placed onto them.  A recent post on another blog to a quick article I had written about things to consider when making a map brought up the issue that not all maps should or need a scale bar or north arrow.  Using north arrows and scale bars has admittedly become rote over the years for me and I felt it was time to take a look at this issue.

Some advocate the use of the north arrow in almost every instance, with few exceptions.   Jon Zeitler, Science and Operations Officer at the National Weather Service Forecast Office in Austin, Texas responded to an email debate about the use of north arrows with:

The addition of a north arrow can never harm a figure, only help with clarity. I’m flexible enough that if it’s presented on the first of similar figures, it can be left off subsequent frames. Also, some figures (e.g., a U.S. map with number of tornadoes per state) don’t need a north arrow. So, while certainly not as “required” as a distance scale, best practice would be to include a north arrow or compass rose.

The use of north arrows does require some critical thinking.  As in this post on Esri’s Mapping Center entitled “Does every map need a north arrow or scale bar?” blog:

I teach my students that a north arrow and scale bar are not necessary on all maps — indeed some should not have them, such as orthographic views of the world. One common mistake I see is a north arrow on a smaller scale map (say the United States) in a Lambert Conformal Conic or Albers Equal Area projection — on these types of map, north is only North along the central meridian (due to the convergence of the meridians toward the pole). But we still have an obligation to help the map reader with scale and orientation, so instead of a north arrow the graticule should be shown. A cardinal rule is that a large scale map oriented such that North is not “up” must have an orientation indicator, most easily shown with a north arrow, since these tend to be larger scale maps.

The City of Santa Monica’s use of orientation on its maps is a great example of needing a north arrow.  For aesthetic purposes, the City’s GIS shifts the display of the city so that north is offset (see below).  Per Mike Carson, the GIO for the City of Santa Monica, the maps are rotated 46 degrees so that the beach is located at the bottom of the map and most of the streets run vertical/horizontal.  The new orientation allows the boundaries of the city to fit better within rectangular sheets of paper.

A map of the city, with north towards the top of the page, looks like this map produced by the Big Blue Bus Company:

Santa Monica Big Blue Bus Lines

Santa Monica Big Blue Bus Lines (click on map for source file).

The City of Santa Monica’s GIS reorients the map so a similar map showing the bus routes within the city looks like this:

Bus Routes within the City of Santa Monica

Bus Routes within the City of Santa Monica (click on image for source file).

When considering the issue of whether or not to use north arrows, it’s good to understand the answers to a few questions about the map before deciding the appropriateness of using a north arrow:

  1. Is the map showing a large area such as a map or the world, or the United States where north orientation would be obvious to most of the general public?
  2. Is north towards the top of the map?
  3. If not, is it clear which direction is north without needing to add a north arrow?
  4. Does the intended audience of the map understand the orientation of the geographic area shown?  As Jerry Ratcliffe from the Department of Criminal Justice notes (tongue in cheek) “Anyway, if you have visitors from outside your suburb, city, or country, why the hell should they want to know which direction is North, so they can orientate themselves? They probably are not interested anyway.

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