How to Edit OpenStreetMap Data

One of the advantages of the OpenStreetMap data used by our Ultra Mileage system, is that you can add your own corrections. Other commercial data providers typically take over a year for their changes to be taken into account. OpenStreetMap changes appear in their master database immediately, and we regenerate our road packs every 1-2 months.

A number of OpenStreetMap editors are available, and the OpenStreetMap Wiki maintains a list. iD and Potlach are online editors that run in a browser, but we prefer JOSM which is a desktop-based Java application.

JOSM is very similar to a conventional vector drawing program. Features are defined as nodes (points) and ways (polylines or linestrings of nodes). Restrictions can be used to define relationships between these – for example, a “no left turn” restriction. Tags can also be viewed or modified for all of these objects.

A number of visual base layers are available, including satellite imagery and the current OpenStreetMap tile renderings. Small extracts of the OpenStreetMap data can then be downloaded for the view area. Here is an example view showing a small area of Houston:

JOSM Screenshot with a section of Memorial Drive, Houston highlighted. Note tags on the right-hand side, and the menu on the left. (Click for larger view)

Here we have selected the eastbound lane of Memorial Drive, and JOSM has highlighted it in red. JOSM has also shown the direction of the way using red arrows. The tag information (on the right) shows the way is marked as a one-way secondary highway.

By downloading and examining parts of the road network it is possible to investigate possible issues and if necessary, fix them. Tags can be changed or added. Nodes can be moved. Or new nodes can be added. Updates can then be uploaded to the OpenStreetMap server.

New roads can also be mapped by importing GPX tracks from a GPS receiver.

JOSM supports a range of plug-ins. For example, the poly plugin adds support for osmosis’s .poly files. These can then be used with osmosis (a command line utility) to ‘cut’ new custom regions of OpenStreetMap PBF files for use with the Ultra Pre-Processor.


Useful Links

Before editing the OpenStreetMap data, it is strongly recommended you familiarize yourself with the OpenStreetMap schema and methodology. Good sources for this information can be found in the OpenStreetMap Wiki, OpenStreetMap Listservers,  and  OpenStreetMap: Using and Enhancing the Free Map of the World by Frederik Ramm, Jochen Topf, and Steve Chilton.

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