Canton Basel-Stadt Building and Address Import

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Canton Basel Stadt Building and Address Import is an semi-automatic import of data provided by the local authorities, covering the canton Basel-Stadt in Switzerland. The import took place in the last quarter of 2017, gaining 98% address coverage. It built on a similar import effort in 2014/2015.

It is now in maintenance mode, filling remaining gaps and keeping up with real-world changes. In February 2018, we reached 99% address coverage.

Goals

The goal is to import building and address data into areas that are not well covered in that respect.

Schedule

The initial import of the badly covered neighborhoods will take place in the last quarter of 2017, and is estimated to consist of less than 4000 buildings/addresses. Later on, the same workflow can be used to further improve accuracy in already covered areas, and to keep up with real-world changes.

Import Data

Background

Data is provided by the authorities of the Canton Basel-Stadt (a Swiss "state", actually the smallest one, only 37km²). The data can be ordered in chunks of at most 3km², but not as a whole.

Data source site: http://shop.geo.bs.ch/geoshop_app/geoshop/
Data license: http://www.geo.bs.ch/geodaten/nutzungsbedingungen.html
Type of license: Public Domain with Attribution
Link to permission: In http://lists.openstreetmap.ch/pipermail/talk-ch/2014-January/002517.html the responsible person states that mentioning the source in the contributors list fulfills the requirement of attribution
OSM attribution (if required): https://wiki.openstreetmap.org/wiki/Contributors#Canton_Basel_Stadt
ODbL Compliance verified: yes, see https://sosm.ch/de/projekte/swiss-open-addresses/

OSM Data Files

Exemplary processed data, ready to be imported:

Import Type

This is a potentially recurring semi-automatic import, with a kickoff phase to gain full initial coverage.

Data Preparation

Tagging Plans

We will tag every building outline with building=yes (or some more specific building type, if known).

We will tag every address with the standard addr:street, addr:housenumber, addr:postcode and addr:city tags. Addresses will be mapped as entrances (as suggested by the imported data), so we will set entrance=yes.

Changeset Tags

Every changeset will be tagged with the source="Geodaten Kanton Basel-Stadt" and description=https://wiki.openstreetmap.org/wiki/Canton_Basel-Stadt_Building_and_Address_Import.

Data Merge Workflow

Team Approach

The neighborhoods to be imported will be listed in the Cantons' wiki page DE:Switzerland:Basel-Stadt. All local mappers are invited to reserve a piece and start the import according to the described workflow. Imports will be uploaded from separate accounts named [username]-import-geodaten-basel-stadt.

The import was discussed on the Swiss OSM local mailing list (talk-ch): http://lists.openstreetmap.ch/pipermail/talk-ch/2017-October/004266.html

Workflow

The import will happen in small chunks (size of one or multiple city blocks). A single changeset should not have more than 200 buildings and their addresses.

Step by step instructions:

  • Order the data for the area to import from the Geodaten-Shop http://shop.geo.bs.ch/geoshop_app/geoshop/ at "Amtliche Vermessung und Grundbuch" / "Amtliche Vermessung MOPublic", as "Esri Shapefile" in coordinate system LV95, select datasets "Bodenbedeckung" (ground coverage) und "Gebäudeadressen" (building addresses). Processing the data typically takes a few minutes, you will get an email with a download link. Unzip the received archive.
  • Add the buildings
    • Open BB_BoFlaeche.shp in JOSM. The JOSM plugin Opendata must be installed.
      • Buildings that have been constructed only recently might be found in BB_ProjBoFlaeche instead. Use this data only if you have verified that the respective building really exists.
    • Extract the buildings by searching for "-Typ=-Gebaeude -type:node or type:node -child" and deleting all selected entities.
    • Select all buildings and "Simplify Area" using the respective JOSM plugin, which removes superfluous nodes, and prunes nodes on round edges. We use the plugin's default settings.
    • Treat the few buildings with inner outlines (relations) manually.
    • For every building outline (not the nodes), add the tag building=yes (or a more specific building type such as "detached" (für ein freistehendes Einfamilienhaus), if you have additional information), and remove all other tags.
  • Add the addresses
    • Open GEB_Gebaeudeeingang.shp in JOSM.
    • For every address, add entrance=yes, rename the tags Lokalisati => addr:street, Hausnummer => addr:housenumber, Ortschafts => addr:city, and PLZ => addr:postcode, and remove all other tags
    • Remove duplicated addresses that are associated with auxiliary buildings.
  • Merge the two added layers
  • Move the entrances onto the building outlines and join them to the building outlines
    • Zoom in so much that entrances and outlines are clearly separate
    • Select all entrances that do not lie yet on a building outline (JOSM search "entrance=yes -child", create a shortcut for that search)
    • Execute "Move Node onto Way" (N) to move the entrances onto the closest segment of the enclosing building outline
      • If nothing happens, zoom out step by step until the nodes are moved
    • Repeat the above until all entrances are on the building outline
  • Conflate the import with existing data
    • Download the respective area from OSM
    • Remove buildings that are obsoleted by the import (e.g. just a single building outline for a whole row of houses)
    • Replace an existing building if its shape is of a much worse quality than the imported one. Preserve the existing tags, relations, and the history by using "Replace Geometry". Otherwise keep the building as is, so remove the to be imported one.
    • Remove existing address interpolations that are obsoleted by the import, and replace existing address nodes that do not match the entrance, again, keeping existing additional tags.
    • If there are many features to conflate in a changeset, you can treat them easily one by one using the TODO plugin.
  • Check everything for consistency, e.g. that
    • the buildings are in the right positions, compare with aerial imagery from the same source
    • the buildings do not overlap roads or natural features
    • the addresses match the adjacent roads (spot test)
    • you import only building outlines and address nodes, nothing else
    • that the validator does not complain about any imported features
  • Upload the change, specifying the changeset tags
  • Some time later, double-check the impact and quality of your imports using the respective QA tools found here: DE:Switzerland:Basel-Stadt#Adressabdeckung

In areas where building outlines already exist, it is at the mapper's discretion to import the addresses only.

If necessary, changesets can be reverted using the respective JOSM plugin. As the changesets are relatively small and little further editing is expected on the short term, few to no conflicts are expected in this case.

Conflation

Conflation will happen manually in JOSM, with the help of the Conflation plugin where needed. See the workflow above for detailed instructions.

Historical Note

An import following similar guidelines has been conducted in 2015/2016, but without review on the Imports mailing list. That import had already covered 80% of the buildings and addresses. For that reason, the import is already listed in Import/Catalogue. The import proposed here aims a continuation of this work backed by standard procedures.

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