To north arrow or not to north arrow?
I started my GIS education back when hand cartography was still a course offered at UCLA. My geography teachers drilled into me a 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.
Using north arrows and scale bars admittedly became rote over the years for me until I took a look at the debate about whether or not a map actually needs a north arrow. Believe it or not, cartographers can become quite passionate over the issue.
The Debate About Using North Arrows on a Map
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. This post by Aileen Buckley on Esri’s ArcGIS blog entitled “Does every map need a north arrow or scale bar?” provides some food for thought on the issue:
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 map 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.
An Example of When to Use a North Arrow on a Map
The City of Santa Monica’s use of map orientation is a great example of the need for a north arrow. For aesthetic purposes, the City’s GIS shifts the display of the city on its maps so that north is offset.
The reason why Santa Monica GIS rotates its maps 46 degrees is so that the beach is located at the bottom of the map and and the grid layout of the streets are now vertical and horizontal with the edges of the page.
The new orientation allows the boundaries of the city to fit better within rectangular sheets of paper. All maps shift the orientation of the north arrow to match the rotation.
A map of the city produced by Santa Monica’s Big Blue Bus Company (the location public bus transportation system) has a layout with north towards the top of the page:
The City of Santa Monica’s GIS reorients the north so a similar map showing the bus routes within the city looks like this:
What to Consider When Using a North Arrow on a Map
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:
- 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?
- Does your map have a reference map or inset map that lets the reader understand already where north is located?
- Is the north direction towards the top of the map?
- If not, is it clear what the direction of north is without needing to add a north arrow?
- Would adding a north arrow help with understanding the context of the area you are showing in your map?
- 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.“
- Will your audience need to compare maps of the same geographic area that have different map orientations? In the case of the Santa Monica bus maps that I discussed earlier in the article, having a north arrow on both maps would help the reader. If a person takes a Big Blue Bus map with its north orientation and then tries to compare routes on a north rotated map produced by the City of Santa Monica, having a north arrow on both maps would be important for context.
This article was originally written September 13, 2011 and has since been updated.