Thursday, October 4, 2012

60 Steps Revisited: Step 55 - Make Clear Maps

Back in 2009, I did a series of posts covering the excellent book Crime Analysis For Problem Solvers. The book is published by the US DOJ's Problem Oriented Policing Center (POP Center). Because of the value I think this book has for crime analysts, and policing in general, I am going to re-post this series on here on the blog.

This post, Step 55 - Make Clear Maps, in our walk through Crime Analysis For Problem Solvers is closely related to the last post, Step 54 - Tell A Clear Story. In fact, given the prevalence of GIS technology and crime maps in most police departments, I'm not sure that you could tell a clear story without making a map. It seems like I am constantly being asked to produce maps for my department. I really think this is a good thing. Maps, help to tell your story and provide context for the information you provide.

To do this, your maps need to help clarify the story you are telling and not "muddy the waters". The authors offer this advice about making maps:

Maps have an important role in telling compelling stories about problems. But they need to be clear to accomplish this. That is, maps must contain as much relevant information as possible and no irrelevant information.
At one time, making maps with a GIS was something that was probably left to someone with special GIS or cartographic skills. However, nowadays with simple to use free tools such as Google Earth or ArcGIS Explorer, it doesn't require the training to make maps that it once did. The downside is that the formal GIS training often included education on proper cartographic principles that made for clear, easy to read maps.

The authors have eight tips for making good maps:
  1. Know what information your audience will find useful (and what information is confusing).
  2. Keep maps simple. Eliminate all features that do not contribute to understanding the problem.
  3. Avoid graphics that draw more attention to themselves than the data.
  4. Include details that help the viewer understand the problem, even if that means adding this information by hand.
  5. Include a scale and, if needed, a compass orientation (usually North is to the top).
  6. Use meaningful gradations to show intensity of hot spots. For example show colors becoming increasingly hot (yellow to red) as the problem worsens.
  7. Apply the correct dimension of crime concentration: dots for places (and sometimes victims); lines for concentrations along streets and highways; and areas for neighborhoods.
  8. Make use of tables and figures along with maps.
It may also help to look at maps others have created to see what makes for a good map. ESRI, the company that makes ArcGIS software has a great series, the ESRI Map Book that has some of the best maps from various industries showcased in it's pages. You can view the Map Book online for free at the link.

Next time, we'll cover Step 56 - Use Simple Tables.

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