Clifford Snow bio photo

Clifford Snow

Clifford is described as an OpenStreetMap Supper Mapper. He started contributing to OSM in May 2011. Hosts OpenStreetMap-Central-Salish-Sea Meetup Group located in Mount Vernon, WA. He help organize the 2016 State of the Map US in Seattle. His prior endeavors include glassblowing, managing an art center facility and telecom management.

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Running Missing Maps Mapathons

Getting Started - Before the Mapathon

  • The Missing Maps checklists are really good for the planners! It even gets down to important things easy to forget, like extension cords and power strips.
  • Recommend people bring a mouse/trackball to the session. The Red Cross may want to have a bag of cheap USB mice to lend. (Who thinks of taking a mouse any more.)
  • Have people sign up1 to OSM before they come. Use the standard OSM signon page. See my diary entry for the signup process. It’s something that needs improving, but that’s a long term project.
  • Again, before they come to the event, suggest that they go add a restaurant, playground, park bench, etc. in their neighborhood.
  • Task selection: Opened up to the public as late as possible. Enthusiastic editors unrelated to the mapathon can be busily completing multiple squares before the event.
  • Task selection: Also, having a beginner backup task available is a good idea.

Beginning of Mapathon

  • Explain Missing Maps and the relationship with OpenStreetMap. We’d really appreciate it if people went away knowing that OSM isn’t just for the developing countries.
  • Explain the task. People will be more diligent if they understand how it impacts others.
  • Most likely the group will need to be split when they arrive. Those who edited and those who didn’t. Get the ones who’ve done an edit into Tasking Manager. Have the others do the sign up and make an edit. We’ve had pretty good luck getting people to install JOSM prior to training classes which is actually more involved than the sign up and walk through steps.
  • The 1-2-3-4 MM instruction sheet also looks great for the new mapper. Focusing on it allows mappers to go at their own pace during the event, and sending it home with them can really maintain their confidence/retention.
  • Considering using the built-in tutorial to iD for big groups. it’s simple, and hands-on.
  • Keeping it simple. Just getting the 1-2-3-4 basics down, and repeating them, is good enough. The temptation is to provide too much information/editing shortcuts too soon. For an editor on their first day, it’s too much.
  • Task selection: Small squares (or instruct the mappers to split their squares). Being able to mark squares as ‘done’ is important.


  • Explain tasking manager and get people started on a task. If everyone is doing the same task, explain what they are working on, what they are expected to map and the appropriate tags. Actually do some editing. Cover concepts like orthogonalize (squaring) buildings. Mapbos has a blog post about customizing id that for specialized use.
  • Task creation: Hopefully tasks requiring only drawing buildings. Even if roads need to be drawn, perhaps saving them for another task/pass at the area. Road priorities may be a little difficult to learn off the bat, and it’s really easy for conflicts to occur when people are mapping roads in adjacent squares.
  • Reminding people to Save Often (perhaps having a timer, and having everyone save when it goes off?). This wouldn’t be vital, but could add to the fun, and there’s nothing worse than losing your work!
  • After people have been editing for a while, take a break and explain more editing concepts2. (Make sure to have them commit their changes first.)
  • Remembering that Tasking Manager tasks timeout after two hours! If your mapathon is longer than that, you could end up with multiple people working on the same square.

Follow Up

  • Having a couple of really good, memorable before/after maps for visual aids for impact.
  • Follow up contact. Again, keeping the number of emails limited and very simple, but maybe providing the before/after map for the area which shows the result of the work.
  • Include links to the Tasking Manager, LearnOSM, where to go for help, etc.
  • It would be good to develop a participant’s survey to better understand how well we are doing and where we need to improve.


  1. Having people sign up and do the first edit locally can give them more confidence. They are the experts when mapping in their own neighborhood.
  2. The concept of adding more instruction after people have gotten started is how we taught glassblowing. We’d spend the first 15 to 30 minutes talking safety then have people actually gather glass from the furnace. (Sounds easy, but when you open the furnace door and feel the heat of a 2000° pot of glass all you can think of is how to get away!) Once they have become comfortable they we introduce new concepts. Not only is it safer, but it’s more fun because you doing something right away. The same can apply to mapping.

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