As the OpenStreetMap community is pretty active here, the local map is quite good and it is very useful to me when doing urban geocaching or just to walk around, especially with OsmAnd, a very good map app.

I had contributed to OSM a while ago while I was in a different region, mainly by posting notes and telling other contributors to fix the map for me. Now I want to do something a bit better and actually contribute myself.

I added a public bookcase and tried to look a little deeper into how traffic signals are mapped because there was one right new to the bookcase. That got me to start a discussion on traffic signals having audio signals for blind people being activated using remotes in France.

I also started looking into two particular things: mapping public drinking fountains, which are commonly found in the city center here, and addings tags on public places with Wi-Fi access, as there are free Wi-Fi hotspots provided by the city among other things.

I also wrote about this on my French blog.

Tagging drinking fountains

• General tag: amenity=drinking_water
  Shown as “Potable water” in OsmAnd
• Specific tag: man_made=water_tap
  Shown as “Water fountain” in OsmAnd
• Potable water: drinking_water=yes/no
• Drinking is forbidden: drinking_water:legal=no
• Can refill bottles: bottle=yes/no
• Hot/cold water: cold_water=yes/no, hot_water=yes/no
• Has a fee: fee=yes/no
• Wheelchair accessible: wheelchair=yes/no
• Operator: operator=…

Tagging internet access

• internet_access
  • yes: Available, not more specific
  • no: Not available
  • wlan: Wireless hotpost (Wi-Fi)
  • terminal: Computers available with Internet access
  • wired: Ethernet plugs available
  • service: People are available to troubleshoot your connection
  • Specific values can be combined: wlan;terminal for example if there are both computers and WLAN.
• internet_access:fee
  • yes: A fee is required to get access
  • no: Free for all
  • customers: Only the customers get free access
• internet_access:operator: Operator of the service, if not the operator of the building itself (aka the general operator key)
• internet_access:ssid: ESSID of the Wi-Fi network.

Note that hotspots that are strictly restricted to a set of persons, even after paying a fee (e.g. Eduroam, company networks, etc.) should not be mapped.

Wi-Fi scanning

Ideally, we need a way to log both the current GPS position and the found networks with their signal strength, which would allow us to later do some triangulation and guess at where the network is. We also need to see the currently detected networks while on the go, as we might be able to guess where they are without having to do a mess of triangulation.

We tried to use an Android app, WiFi Tracker, but it does not work on my phone and is quite power-hungry. Additionally, on Android 9, Wi-Fi scanning is limited and lifting the restriction is only possible in the developer options in Android 10+.

We developed an ESP32-based scanner, and I worked on wrangling its output into a database to help with mapping. We blogged a lot about it:

• My friend’s post on the topic
• Importing GPX files into SpatiaLite
• Importing GPX files into PostGIS
• The Wi-Fi scanning adventure
• Importing Wi-Fi scan results into PostGIS
• Building a map of Wi-Fi access points
• Mapping Wi-Fi access points on OpenStreetMap
• Identifying Wi-Fi access point manufacturers
• Building a heatmap of Wi-Fi access points:
  • Counting the Wi-Fi results per pixel
  • Downloading a PNG map from OpenStreetMap in SQL
  • Generating an image of the Wi-Fi counts in SQL
  • Assembling the heatmap in SQL