Digitization in OpenStreetMap

OpenStreetMap (OSM), is a collection of geospatial data built by a community of mappers that contribute and maintain data about roads, trails, caf├ęs, railway stations, and much more, all over the world. While the site is often thought of as the OSM web map that is similar to Google Maps, the primary focus of the OSM project is the collecting and disseminating of the data itself.

The project was initially started by Steve Coast in 2004 following the lead of Wikipedia as an open-source encyclopedia. As with open-source software, the open data model contrasts with the proprietary data model under the belief that community is stronger by standing on each other's shoulders rather than standing on each other toes.

As of 27 August 2016, OSM had around three million users, and the OSM database contained around 3.5 billion nodes (lat-long points) and around 365 million ways (line or polygon features).

The community emphasizes:

The Humanitarian OpenStreetMap Team

One notable area in which the OSM community has been useful is in providing free, current map data to relief organizations responding to environmental disasters or political crises. While commercial data services (like Google) can make a profit maintaining geospatial data on developed, wealthy areas of the world, there is less commercial incentive to expend effort mapping the less developed areas of the world. This absence of geospatial data can be a major hinderence to humanitarian organizations.

When major disaster strikes anywhere in the world, the Humanitarian OpenStreetMap Team (HOT) rallies a huge network of online volunteers to digitize maps that enable responders to reach those in need. If you have an interest in the developing world, you should read more about their efforts and volunteer opportunities on The Humanitarian OpenStreetMap Team website.

The Humanitarian OpenStreetMap Team

Some Key Terms

An editor is a program or website you can use to edit the map. iD, (the in-browser editor on the OSM web map) is probably the easiest course of action, but if you think you might get more deeply involved in OSM (and/or you have a broader technical interest in open-source GIS) you might try downloading and using the JOSM desktop editor.

A node is a point on the map, like a single restaurant or a tree.

A way is a line or area, like a road, stream, lake or building.

A field or tag is a bit of data about a node or way, like a restaurant's name or a road's speed limit.

Logging in to OpenStreeMap

To be able to digitize in OpenStreetMap, you need an account, which you can get by pressing the Sign Up button at the top right of the screen at OpenStreetMap.org.

You will need to pick a display name. While using an alias to preserve your anonymity and prevent harassment is generally considered a good practice, use of a variant on your real name can facilitate better communication if you are already a public figure, or if you want professional credit for your contributions.

You might also consider using a personal e-mail rather than an institutional e-mail to avoid any potential conflicts of interest, or the loss of access to your account when you leave the institution.

Once you have an account, you can press the Log In


Digitizing Houses

Zoom in to the area that you want to digitize.

Press the Edit button and select Edit with ID (in-browser editor).

Press the Area button and draw an outline around the building, clicking the mouse to add corners (vertices).

Double-click when you have entered your last corner.

If your building an ordinary building with walls at right angles, click on one of the edges and press <Shift>-S to square the angles.

Digitizing a House in OpenStreetMap

Adding Tags

In the left panel you are given an option to Select feature type. For a house, choose Building features and House.

You will need to find the address of the building. Many county assessors provide web maps for accessing parcel (property) information. For this example in Nassau County, we use the Nassau Caounty LRV Internal Viewer.

Find the building you digitized in the parcel map. In neighborhoods like this example where there are long rows of similar buildings, you will want to search based on street names, intersections, and, in some cases, you may need to count buildings from street corners to find the correct property. In this case this house on Beechwood Street is on the Nassau County / Suffolk County border, making it a bit easier to find.

For a house, you should enter the address as five different tags:

Adding Tags in OpenStreetMap


When you have finished digitizing (or if you are in the middle of a long session of digitization) you will want to save and upload your changes. Changes you make in the browser will be lost unless you save.

Give some brief explanation for your changes.

You can return to regular OpenStreetMap view by clicking on the logo at the left top of the page.

Changes you upload will take some time to update the main map tiles, so you may not see them when you go back to regular view. However, you may want to check back in an hour or so to verify that your changes were successfully uploaded.

Saving and Uploading Edits