Clifford Snow bio photo

Clifford Snow

Clifford is described as an OpenStreetMap Supper Mapper. He started contributing to OSM in May 2011. Hosts OpenStreetMap-Central-Salish-Sea Meetup Group located in Mount Vernon, WA. He help organize the 2016 State of the Map US in Seattle. His prior endeavors include glassblowing, managing an art center facility and telecom management.

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Mapping Sidewalks a HowTo

How to Manually Map Sidewalks as Separate Ways

This guide will help you map your cities sidewalks as separate ways. The other method is mapping sidewalks is as an attribute to street centerlines. Without going into the pros and cons of the two methods, we are just going to focus on how to map sidewalks a separate ways. This was update on May 31, 2019 to include more images, features you’ll run into while mapping, and links to the OSM wiki.

The goal is to build a network of routable sidewalks, especially for people with limited mobility. AccessMap.io show the power of OSM to help people navigate their city on foot or in a wheelchair.

While I have you here, I want to give a shoutout to the University of Washington’s Taskar Center for Accessible Technology . The director, Anat Caspi and project lead, Nick Bolton, were the ones that convinced me that we need to change how we map pedestrian ways. They developed the OpenSidewalk Project and AccessMap.io. They are the inspiration behind mapping sidewalks in OSM.

Tools you’ll need

  1. JOSM - Note iD is very well adapted to mapping sidewalks. I’m just more accustomed to using JOSM.
  2. Tasking Manager to help break the area into manageable chunks.
  3. Good satellite imagery
  4. Street level imagery which can be Bing StreetSide, OpenStreetCam or Mapillary. The last two allow you to capture the street level imagery from your car, bike and even walking.
  5. JOSM sidewalk mapcss file. Download the file and point to it in JOSM.
  6. Tasking Manager to break the collections into small chunks
  7. QGIS to find sidewalk islands

Sidewalk terms

  1. footway. What we call sidewalks in the US is called a footway in England where OSM got it start. A footway is a pedestrian path between any two points. highway=footway
  2. sidewalks. A sidewalk is a footway that run parallel to a street. highway=footway + footway=sidewalk
  3. crossing. A street crossing is either a marked or unmarked crossing of a street. highway=footway + footway=crossing + crossing=marked|unmarked
  4. Marked/Unmarked Any crossing that is marked on the street should be tagged as crossing=marked. The marking can be just two parallel lines, stripping, or even intricate patterns. This interpretation differs from the wiki which is confusing.
  5. crossing islands. Crossing island are small places usually between two lanes of traffic. Tag the short way as crossing:island=yes
    Traffic Island
  6. curbs. In British English its kerb. There are many flavors of kerbs. Here are some of the common ones you’ll likely see:
  • Lowered A lowered curb cut should be wide enough for a wheelchair to use. There should be no more than a 1 inch difference between the street and the curb. also referred to as a sloped curb or curb ramp. kerb=raised lowered curb
  • Incline An attempt to create a lowered curb. Using JOSM to measure the length and estimate the height of the curb to determine incline. Most curbs are 6” high but not all. Split the way at the end of the regular sidewalk. Draw the way to indicate movement upward. highway=footway + footway=sidewalk + incline=8% asphalt lowered curb
  • Flushed A flush curb is level with the pavement kerb=flush flush curb
  • None If there is no curb, tagging the end of the footway with kerb=no
  • Raised A curb with more than a 1 inch difference with the street. kerb=raised raised curb
  • Rolled Rolled curbs still provide a gutter for water while being traversable by large wheeled vehicles, such as cars and bicycles, but not wheelchairs kerb=rolled No image available

Mapping

Sidewalks

A good place to start is to map sidewalks in city blocks around one intersection before adding the crossings. If the imagery is sufficiently sharp you should be able to easily add the sidewalks. Occasionally you’ll need to consult street level imagery to see below tree and other blocked views.

Add Sidewalks

The next logical step would be to add curbs. This is where street side imagery is needed. Both JOSM and iD have integrated the three street side packages into their editors.

Curbs

Determine if a curb ramp exists and if so, what type and is there a tactile pad. Adding the tactile pad is important for people with vision impairments. Adding a short footway between the curb with a ramp and the sidewalk would be a good idea. I don’t, basically because marking a curb ramp in the footway doesn’t impact routing for people with limited mobility and since most curb ramps extend into the way, it’s a good signal to someone with vision impairments that they reached a curb ramp.

Add Curb Raised Curb with Step

Tactile Pad

Crosswalk

Next add the crosswalks. Use highway=footway + footway=crossing + crossing=marked when the intersection is marked for pedestrians or crossing=unmarked when the crossing isn’t marked. Include a pedestrian crossing node where the street intersects with the crosswalk. It’s purpose is to notify vehicles of the crosswalk. While you are there, check for stop signs and traffic lights to add to OSM.

Add Crosswalk Raised Curb

Traffic Island

If there is a island between lanes of traffic, add a way, crossing:island=yesTraffic Island

Wheelchair Ramps

This is a special case where there is a wheelchair ramp, usually to a business. It should be mapped as highway=footway + incline=x%. Use JOSM to measure the length of the way and estimate the height to calculate the percent incline. Wheelchair_ramp.jpg

Mapping Tips

  • Mark sidewalks that end without access to the street as kerb=no
  • Mark sidewalks that end in the yard with kerb=no
  • If the sidewalk has a raised curb, add an extension to the sidewalk otherwise the router will thing their is a raised curb preventing wheelchair routing. Improper Raised Curb
  • Remove any existing footway that connects directly to the road without a crossing. Remember, we are trying to keep pedestrians on the sidewalk.
  • Include steps and ramps
  • Indicate obstruction areas that block wheelchair access with wheelchair=no Obstructions
  • Add surface=* especially if the surface is gravel or other material that would impair or prohibit wheelchair access.
  • If working from Tasking Manager, pick a strategy, such as working blocks from south to north and east to west. This will help you not miss intersections.

Finding Islands

No not that kind of island. We are looking for sidewalks that don’t connect to the pedestrian sidewalk network. For this you’ll need QGIS. Install QGIS using the directions provided on the website. In QGIS, using the Plugin manager, install the Disconnected Island plugin. The python module NetworkX is also required. It can be installed with pip install networkx --user

To get the data needed to find islands, run the following overpass-turbo script. Replace your_area with either the city or bounding box of your sidewalk network. The script collects curbs and traffic signs and signals in addition to footways. Having this additional information allows view the entire pedestrian network in QGIS.

[out:json][timeout:25];
// fetch area “your area” to search in
->.searchArea;
// gather results
(

  node["kerb"](area.searchArea);
  node["highway"="stop"](area.searchArea);
  node["highway"="traffic_signal"](area.searchArea);
  way["highway"="footway"](area.searchArea);

);
// print results
out body;
>;
out skel qt;

Export the results to a geojson and load into QGIS. Run Vector->Disconnected Island->Check for Disconnected Islands Disconnect Islands Plugin

The result should look like

Disconnect Islands

Unchecking just the most common footway results in

Disconnect Islands

Check each island to verify that no connections were missed.


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