Improving OSM Data — One Virtual Mapathon at a Time

Critigen’s Open Data & Development team hosted an online mapathon during Geography Awareness Week to contribute to OpenStreetMap. Unlike traditional mapathons that typically digitize new features, our team tested a new approach, a different user interface, and a focus on correcting map errors.

Mapathons 101

Traditionally, mapathons are organized to bring communities together to map environments important to their locality. Today, new tools and technology have expanded the scope and lowered barriers for participation — making it easier for mappers to contribute various themes and features. Mapping can refer to either tracing something using aerial photos (like a building), or correcting the digitization of something that’s malformed and/or against mapping standards (improperly mapped roundabout).

OpenStreetMap (OSM) is a collaborative project that aims to create a free, editable, open map of the world. It provides an excellent interface for communities around the globe to contribute their local knowledge and map their own communities. Hosting an OSM mapathon provides immediate feedback and support to these communities. To contribute our efforts to Geography Awareness week, Critigen created a virtual OSM mapathon. In the following sections, we’ll walk through the conceptual arrangement and planning of a mapathon, Critigen’s experiment, and observations from our inaugural virtual mapathon.

Getting Started

Hosting a successful mapathon is similar to hosting a focus group; a clear purpose and focused theme, effective marketing and communication, engagement of participants with similar interests, and inclusive event space are all essential ingredients. In addition, having facilitator(s) that are familiar with the OSM data model and mapping best practices is key. Here are some tips to assist you in your mapathon planning:

  • The purpose should be simple. What do you want to accomplish with your participants? Examples include: digitizing parks, squaring and closing buildings, or realigning roads using aerial photos or satellite imagery.

Experimental Mapathon: New approach, platform, and mapping content

To celebrate Geography Awareness week at Critigen, we organized a company-wide mapathon with a twist: 100% virtual. The planning and preparations were slightly different than conventional mapathon. Here’s how we set it up:

  • Uploaded MapRoulette Challenges for 24 US and 2 UK cities based on staff locale.

Lessons Learned

Our virtual mapathon experiment was a hit from the beginning. In the first two months, we collected more than 800 edits from 27 different contributors (25% of participants were new mappers!).

Completion Stats for Our Mapathon

Three main takeaways emerged from our experiment:

  • Keep it simple. Most edits were simple geometry fixes because it required the least amount of research. For attribution-based map errors, the challenge difficulty was heavily dependent on resource availability. For example, without great street-side imagery, correcting and validating speed limit tags is virtually impossible. Mapathon organizers should evaluate the feasibility of edits when creating tasks that rely on different resources. In addition, providing fix scenarios could help facilitate edits. For instance, when flagging an address point that’s missing a road name, providing nearby street names for mappers to select from may be an easier editing task than having them research surrounding roads to find the correct name. Keeping tasks simple and small allows mappers to get into a rhythm and really crank through some fixes!
Example editing task for the Spiky Building Check
  • New theme: correcting map errors. The locality is always important in conventional mapathons so that participants can feel engaged and contribute their local knowledge to the map. Our experiment populated 26 cities based on where Critigen staff are located. However, we observed that participants preferred working on editing tasks they were interested in (e.g. feature types or attributes), rather than focusing on making edits in specific cities. We noted that locality was a minor factor to consider when developing tasks, particularly when correcting map errors was the event’s theme. Over time, as OpenStreetMap is becoming “complete”, we’ll all need to focus on perfecting map quality and finding some smaller scale changes and fixes.

It’s Your Turn!

We enjoyed hosting a virtual mapathon, here are some ideas to make the most of your experience:

  • Host simple editing tasks and make sure all resources (aerial and/or street-view) are available (by reviewing sample tasks).

Mapping new features can be fun, but correcting map errors makes OSM better. By sharing our experience, we hope to inspire more mapathons to focus on improving OSM data quality in the future!


Critigen serves non-government organizations…


Critigen serves non-government organizations, not-for-profits, private and public donors to implement technology solutions that improve the efficiency and effectiveness by which our partner organizations achieve their missions.

Muning Monica Brandeis

Written by


Critigen serves non-government organizations, not-for-profits, private and public donors to implement technology solutions that improve the efficiency and effectiveness by which our partner organizations achieve their missions.

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