invalidAccessTagCheck.md

Invalid Access Tag Check

Description

This check flags roads with misused access=no tags.

Misuse is measured by a lack of supporting tags. Tags, such as public_transport=yes, can be paired with access=no to indicate what does or does not have access. If one or more of these supporting tags are present, access=no is valid.

Live Example

The way id:440449063 has an invalid access=no tag, as there are no supporting tags.

Code Review

The first step is to filter out objects that contain tags that could be used to support an access=no tag.

The following is a filter that is defined in the configuration to do so.

"tags.filter":"public_transport->!yes&psv->!yes&bus->!yes&emergency->!yes&motor_vehicle->!no&vehicle->!no&motorcar->!no"

In Atlas, OSM elements are represented as Edges, Points, Lines, Nodes & Relations; in our case, we’re working with Edges and Lines.

The next step is to filter in roads, and make sure they have the tag access=no.

The following does so by looking for Edges and Lines with a highway tag containing a value greater than a minimum, and the access=no tag. In Atlas roads can only be Edges and Lines, and the minimum value ensures that things like trails and bicycle paths are not included.

@Override
    public boolean validCheckForObject(final AtlasObject object)
    {
        return AccessTag.isNo(object) && ((object instanceof Edge) || (object instanceof Line))
                && Edge.isMainEdgeIdentifier(object.getIdentifier())
                && !this.isFlagged(object.getOsmIdentifier()) && isMinimumHighway(object);
    }

The test for a minimum highway value is handled by the following. It uses built in Atlas methods and highway value priorities.

private boolean isMinimumHighway(final AtlasObject object)
    {
        final Optional<HighwayTag> result = HighwayTag.highwayTag(object);
        return result.isPresent()
                && result.get().isMoreImportantThanOrEqualTo(this.minimumHighwayType);
    }

Finally, there is a test made to see if the road is inside a military zone. Roads in military zones do not require any supporting tags to be validly tagged with access=no.

The following performs this test by checking for the road being checked inside all Areas and Relations that have a landuse=military or military tag.

private boolean isInMilitaryArea(final LineItem object)
    {
        for (final Area area : object.getAtlas()
                .areas(area -> Validators.isOfType(area, LandUseTag.class, LandUseTag.MILITARY)
                        || Validators.hasValuesFor(area, MilitaryTag.class)))
        {
            final Polygon areaPolygon = area.asPolygon();
            if (object.intersects(areaPolygon)
                    || areaPolygon.fullyGeometricallyEncloses(object.asPolyLine()))
            {
                return true;
            }
        }
        for (final Relation relation : object.getAtlas().relationsWithEntitiesIntersecting(
                        object.bounds(),
                        relation -> (Validators.isOfType(relation, LandUseTag.class, LandUseTag.MILITARY)
                                || Validators.hasValuesFor(relation, MilitaryTag.class))
                                && relation.isMultiPolygon()))
        {
            try
            {
                final MultiPolygon relationPolygon = new RelationOrAreaToMultiPolygonConverter()
                        .convert(relation);
                if (object.intersects(relationPolygon)
                        || relationPolygon.fullyGeometricallyEncloses(object.asPolyLine()))
                {
                    return true;
                }
            }
            catch (final MultiplePolyLineToPolygonsConverter.OpenPolygonException e)
            {
                continue;
            }
        }
        return false;
    }

To learn more about the code, please look at the comments in the source code for the check. InvalidAccessTagCheck.java