OpenStreetMap Inspector helps you improve OSM data

The OpenStreetMap contributors at GEOFABRIK have been doing good things for OpenStreetMap for years. One service, called OSM Inspector, highlights potential errors in the OSM database so that OSM contributors can inspect and correct them. The potential errors are presented in several themes including highways, waterways and administrative boundaries. Some of these layers examine OSM data in one area and others serve the entire planet.

New OSM Inspector routing layer

The most recent addition to the GEOFABRIK OpenStreetMap Inspector is a routing layer for the rest of the world. They’ve had a layer that tested routing in Europe for a while, the new part is that these tests are now extended to the rest of the world as well. And the result is an interesting view of some parts of North America.

OSM Inspector shows potential routing problems such as major roads that approach each other within 5m without connecting.

This view from OSM Inspector shows a pattern of duplicate ways in Indiana as blue lines, and a pattern of unconnected ways in Ohio as red dots.

This view of potential errors is very helpful to check and improve the data in your local area. While one could check OSM Inspector in one window with an editor in another window, GEOFABRIK makes it even easier. OSM Inspector can be used as a background layer in OSM editors.

OSM Inspector in JOSM

To use an OSM Inspector layer in JOSM install it as a background imagery layer.

Follow the numbered steps to add OSM Inspector layers to JOSM.

  1. Open the preferences dialogue and select the “WMS/TMS” tab.
  2. Add a new WMS/TMS layer by pressing the “+” button
  3. Add a name for this layer in the Menu Name text box. Perhaps “OSMI routing”.
  4. Add the WMS service URL in the Service URL text box.
  5. Press the “Get Layers” button.
  6. Select the Routing layer from the layer list.
  7. The Imagery URL will be filled in automatically when you select the layer from the list.
  8. Select “OK” to complete adding the new imagery layer.
  9. Select “OK” again, to complete your preference changes.

You should now see “OSMI Routing” as an option in the Imagery menu. If not, restart JOSM.

To use OSM Inspector layers select them from the Imagery menu. Try moving the OSMI Routing layer to the top of the layer stack, and reducing the opacity of the layer so that you can refer to both the OSMI routing layer, and an aerial imagery layer at the same time. Inspect the potential errors highlighted by the OSMI Routing layer and determine if they are, in fact, errors. If so, fix them!

OSM Inspector in Potlatch 2

OSM Inspector can be used as a background layer in Potlatch 2 as well. Use the GEOFABRIK site to find an area near you with potential routing errors. As ever, your contributions to OpenStreetMap are most valuable when you have personal knowledge of the places that you edit. Navigate to that area on and zoom in to a reasonable editing bounding box. Select the edit tab to start Potlatch 2.

  1. Select Background from the Potlatch Menu bar, then press the “Edit” button to add a new background layer.
  2. Press the “add” button at the bottom of the background imagery dialogue box.
  3. Add a suitable name such as “OSMI Routing” to the Name text box.
  4. Add the new URL$z/$x/$y.png
  5. Press “X” to close the background layer dialogue box.
  6. Select the OSMI Routing layer from the Background menu.

You might find that the potential errors highlighted by OSM Inspector are easier to see if you choose another map style. Try selecting “Wireframe” from the Map style menu.

Do you find OSM Inspector helpful?

Do you find OSM Inspector helpful? Many OpenStreetMap contributors do. Have a look some time at the other great services that GEOFABRIK provides to the OpenStreetMap community. I like the history animations, and the country and region planet extracts are very popular as well.

You can help GEOFABRIK to make OSM Inspector service even better through sponsorship. Sponsoring OSM Inspector will allow more frequent updates of the data, additional analyses and wider geographic coverage of the services.


OSM Inspector has little “P” and “J” icons above the map. Clicking those will open Potlatch or JOSM editing windows with the same bounding box as the OSM Inspector window. JOSM must be running already. Be sure to zoom in to a reasonable (small) bounding box size first.

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