This article was written for relatively experienced OpenStreeMap contributors. If you wish to learn how to contribute to OpenStreetMap, I recommend starting here.

Important tags for pedestrian ways

SonarVision’s itinerary router generates trips which uses pedestrian-only ways in priority.

Here are the most important ones.

Sidewalks

Wiki link

• highway=footway

• footway=sidewalk

Crossings

Wiki link

• highway=footway

• footway=crossing

The two following tags are very important for pedestrian routing and a blind user’s understanding of their surroundings. They will soon be integrated into our calculator.

• crossing=uncontrolled|traffic_signals|unmarked

• traffic_signals:sound=yes

Tags such as tactile_paving=* are interesting as well. Mapping them can help cities find missing or damaged tactile paving, and SonarVision could one day warn users they are missing as well.

Traffic islands

Wiki link

• highway=footway

• footway=traffic_island

We have prioritised this tag because a blind person is very vulnerable at crossings split into two or three sections by traffic islands. This tag is explicitly announced to users in the SonarVision app.

It is fair to sometimes wonder whether or not a traffic island is worth mapping in OpenStreetMap: my opinion is that you should only map traffic islands which are equipped with two tactile pavings, allowing blind users to confirm the information provided by SonarVision with their white canes or their feet and to have a large enough space to wait safely.

Stairs

Wiki link

• highway=steps

• incline=up|down en fonction du sens de la ligne

Unlike for wheelchair users, stairs aren’t a major obstacle for visually impaired SonarVision users. That said, they still pose a risk—especially when going down.

Stairs are explicitly announced in SonarVision.

Other pedestrian ways used by SonarVision

• highway=pedestrian Wiki link. Use this on pedestrian streets, where people can freely walk across the entire width of the road.

• highway=path Wiki link. Use this for paths and trails. This tag is currently given a negative weight in the SonarVision routing engine because the vast majority of our users rely on the VPS system, which does not work on most trails. Learn more: Visual Positioning System GNSS RTK

Mapping recommendations for routing

Map walkable ways using a line following a simple and obstacle-free path.

• Follow the “center” of a sidewalk, crossing, staircase…

• Avoid permanent obstacles (bus stops, benches, parking spaces…)

• A sidewalk becomes a crossing at the kerb. This might be a little bit of a pain to map, but mapping as closely as possible to reality allows us to deliver the instruction with perfect timing (SonarVision warns the user they are in front of a crossing exactly 1m50 before the mapped start of the crossing).

Here is what the ideal mapping of an intersection looks like :

Here is what an ideal mapping of a traffic island looks like. Note that, here too, the crossing becomes a traffic_island at the kerb.

Here is the ideal mapping of a staircase. Please note that the sidewalks and crossings on the bridge are tagged with layer=1 and bridge=yes to avoid them intersecting with the elements below.

Area based mapping

There exists regions where sidewalks are mapped as areas. This might allow for a pretty render on some maps, but it is almost never used for itinerary routing.

Every time SonarVision imports OpenStreetMap data, we filter (delete) all elements tagged with area=yes or type=multipolygon

Indoor routing

SonarVision now works indoors in select locations : Does SonarVision work indoors?

However, in most cases, SonarVision doesn’t work indoors, so we filter out all elements tagged with indoor=yes

Choosing an OpenStreetMap editor

ID

https://www.openstreetmap.org/

I recommend using ID for its great preset manager and its ease of use to edit a few elements at a time. All pedestrian presets it contains are compatible with SonarVision’s itinerary router.

JOSM

https://josm.openstreetmap.de/

For more ambitious mapping projects, you will need to create thousands of sidewalks and crossings. From the tagging perspective, any object you will add will be closely related to one of the 6 following presets :

• Sidewalk

• Unprotected crossing

• Unmarked crossing

• Crossing with traffic lights

• Crossing with traffic lights and audio signals

• Traffic island

Most of the other elements have long since been added to OpenStreetMap : highway=path, highway=pedestrian, highway=steps…

The problem is that ID does not yet have a good shortcut system for presets. You must draw the element, then go click on the preset on the left, so on and so forth, forever. That is where JOSM truly shines: you can import a preset file, add them to your toolbar, then create keyboard shortcuts for them.

1. Download our preset file :

2. Add it to JOSM

3. Add the presets to the toolbar

4. Add keyboard shortcuts for these presets.

It might take you ten minutes to set this up in JOSM, but it will save you a ton of time and help preserve your mental health if you plan on mapping large areas on OpenStreetMap.

Simplified routing engine overview

Each day, at midnight (UTC+01:00), SonarVision downloads all the changes made that day on OpenStreetMap and updates its own copy of the OSM world map.

Re-computing a routing graph and running a world scale routing engine is a task which requires a ton of RAM and processing power, so in order to lighten the load a little, we only keep a portion of the world and we filter out ways which will never be used by pedestrians anyway (essentially high-speed ways).

We then recompute the routing graph on all the remaining ways in this area.

Using SonarVision’s routing engine to validate your OpenStreetMap contributions

The quickest way is to test with Graphhopper’s web interface, the calculator we use and which we have left in public access for the time being.

Otherwise, if you really want to check how trips are generated for SonarVision’s end users, you can create an account.

Please reach out to us if you need anything else :
contact@sonarvision.fr