OpenStreetMap- An Open Source Geospatial Data Hub

The geospatial community benefits greatly from the free and open-source contributions of its members. From databases to forums, to Twitter threads, GIS practitioners are constantly sharing data and tradecraft knowledge. In fact, the majority of geospatial analysis and data visualizations are conducted using free and open-source data and software, and one of the most robust platforms for developing, editing, sourcing, and visualizing this data is OpenStreetMap.

OpenStreetMap (OSM), is often referred to as the Wikipedia of the GIS world; like the popular community-built online encyclopedia, the spatial data in OSM is maintained and verified by the public. Started in 2004 by Steve Coast, a student at the University College London at the time, the platform quickly became a hub for mapping enthusiasts, eager to contribute to a central database for spatial information. Using aerial imagery, local sources, static maps, and on-the-ground intel, OSM contributors digitize building footprints, roadways, and countless other types of infrastructure, adding detailed attribution where possible. 

The Structure of OpenStreetMap

Specifically, there are three elements of data that can be edited in OSM: nodes, ways, and relations. Nodes are singular points, ways are collections of nodes (i.e., lines), and relations are groupings of nodes and ways. When contributors digitize or edit any of these components, the metadata of the contribution (including the editing user, a timestamp, and any tags that the editor wants to include with the data) is saved along with it. Other volunteers validate the contributions of the editors to ensure a degree of checks and balances to encourage data integrity.

Because the OSM interface is especially user-friendly, it doesn’t require a high level of geospatial expertise to edit or use. Jennings Anderson, a geoinformation research scientist who has studied the evolution of OSM in depth, spoke about the wide range of participating OSM members.  

“We have the humanitarian mappers in OSM: people who are focused on contributing data from a humanitarian perspective,” said Anderson. “We have hobbyists that have been around for years, contributing very specific niche knowledge here and there. We now have a large community of corporate actors, who are contributing data presumably in relation to their corporate interests and their data use case.” 

The OpenStreetMap Community

Skilled and amateur mappers often come together after natural disasters or emergencies and quickly edit the spatial data to reflect changes to an environment. This provides important updated information for first responders, and other organizations providing aid. 

The foremost group conducting this emergency response mapping is the Humanitarian OpenStreetMap Team (HOT). According to their website, HOT is composed of personnel from all across the globe, “dedicated to humanitarian action and community development through open mapping.” By editing and contributing to OSM before, during, and after disasters, they mitigate and reduce the risks and damage from these emergencies. 

Anyone can volunteer with HOT, and they always have an ongoing project that needs mapping support; as soon as these contributions are made, they are validated by other OSM users, and added to the database. 

OpenStreetMap Download Tools

You don’t have to be a first responder to benefit from the results of a mapping campaign. Users can download nodes, ways, and relations directly from the OSM website, as well as through a variety of third-party exporters, which are especially helpful for larger or more specific data pulls. For example, Overpass Turbo is a web-based platform for filtering and downloading OSM data using the Overpass API; using their query wizard, even inexperienced users can specify and retrieve data relevant to their mapping project. Unlike exporting directly from OSM, the results of an Overpass query (or an extract from Planet.osm) can be downloaded as a geoJSON, which makes for easy import into your preferred geospatial software platform. 

Overpass Turbo is a web-based platform for downloading OSM data using queries and bounding boxes.

Geofabrik is another OSM data download manager. Users can browse through their website to download bulk OSM data by region or country. Notably, Geofabrik also houses historical extracts of OSM data, which is key for analyzing change in a given AOI or assessing data availability on a certain date.  

If you prefer to browse OSM data before you download it in bulk, QGIS has a plugin for you! After downloading and installing the “OSM Place Search” plugin, QGIS users can activate a search panel to identify relevant features in the OSM database. Then, the user can pick individual features they would like to add to their map. 

OSM Place Search is a QGIS plugin that is used to search for relevant features for use in GIS projects.

Impact of OpenStreetMap

OSM data is free to use by anyone, for any project; the only requirement is that users credit the OSM community in their publications. Countless projects cite OSM as the underlying data source for their complex data visualizations and analytics, and OSM is often used as a validation tool for other digitization and mapping efforts. 

There are map games, biking and hiking route planners, cartographic tools and styles, weather apps, and fitness trackers that rely on OSM. Even state and federal government agencies use OpenStreetMap data as a baseline for many of their more complex defense, intelligence, energy, and security efforts. The products using OSM data are helping people plan more accessible communities, make public transportation more efficient, identify food deserts, and assess damage in war zones. 

Stamen generates creative and artistic map styles for use as basemaps on other projects; their underlying data source is OSM
As Patricia Solis says, OSM is a community of communities. Contributions come from novice map enthusiasts, local experts, humanitarian relief personnel, and corporate entities, each of which is backed by a unique knowledge base and varying degrees of manpower (and womanpower!). There are several robust and ongoing services that package and deliver the data, and others that rely on it for their results. It is impossible to say how many people are using the OSM data at any given time, but thousands of GIS professionals gather every year to discuss open source projects, and at the heart of these conversations is the backbone of open source geospatial data: OpenStreetMap.